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'[OT]: Robotics with PIC16F877 anyone??'
2000\12\07@112351 by Dan Michaels

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Henry Low wrote:
>Good Day to one and all,
>    I am currentlu using PIC16F877 for controlling a simple obstacle
>avoidance autonomous robot. Anybody has done anything similar before and is
>willing to share his/her experience with me?? You may email directly to me
>so that others will not get frustrated over our discussion. But of course,
>open discussion is beneficial to all and that's what this discussion list is
>all about.
>

Hello Henry,

Robotics is not too alien a topic for piclist. In november, there
was a lot of discussion of this in the thread called "How to control
a motor" -[threads don't always stay on the "original" issue].

Plus there are a few of us who have at least a passing interest in
robotics, and a strong interest in autonomous vehicles - me, for one.
I am currently designing a botboard SBC based around a PIC40 - 74/77/..

You should, however, change the topic to [OT]: to keep the hardcore
[PIC]:+purists happy.

How "autonomous" is your robot? Finding the '877 adequate to the
task?

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\07@124152 by Henry Low

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> Hello Henry,
>
> Robotics is not too alien a topic for piclist. In november, there
> was a lot of discussion of this in the thread called "How to control
> a motor" -[threads don't always stay on the "original" issue].
>
> Plus there are a few of us who have at least a passing interest in
> robotics, and a strong interest in autonomous vehicles - me, for one.
> I am currently designing a botboard SBC based around a PIC40 - 74/77/..
>
> You should, however, change the topic to [OT]: to keep the hardcore
> [PIC]:+purists happy.
>
> How "autonomous" is your robot? Finding the '877 adequate to the
> task?

hi Michaels,
   I have been surfing the net for similar robotic applications using the
PIC16F877 but I just could not find any useful materials. My robot is really
simple, its sole objective is obstacle avoidance and being able to move
around the room without getting stuck. After I have achieved that, I might
add on a mapping feature to it or a "seeking warmest object task".
Anyway, why did u ask "Finding the '877 adequate to the task?", isn't 877
quite sufficient for my application?? It has got PWM output, and sufficient
I/O lines for me i think. Actually, I am a real newbie in programming this
chip, in fact this is my first time working with microcontroller. I wonder
if source code of other PIC chips are useable for 877?? I hope to get some
relevant source code of similar nature (like motor control, sensor
interface) for reference so that I may pick up the fun faster.
   Hope to hear from you soon.

Regards,
Henry

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2000\12\07@125553 by jamesnewton

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If you are new to microcontrollers, I would recommend
http://www.piclist.com/piclist/begin

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{Original Message removed}

2000\12\07@130211 by rchock, Steve

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Henry,

I am doing a project that is exactly like yours. I am using a PIC16F873
running at 4MHz. I am using 2 dual H-BRIDGE ckts to drive my motors. I am
using two DC motors for movement. My vehicle uses a set of tank tracks.
Using
this set-up I am able to move FWD, RVS, CCW (slow), CCW (fast), CW (slow)
and
CW (fast). I am using 4 optic reflective sensors to tell the MCU that there
is something by the robot (not quite perfected yet, some materials don't
reflect
very well!!). The optic sensors are interfaced to the PIC using
a quad comparator (LM339). It has 7 LEDs (3 green, 4 red) to display
different
patterns, depending on it's "behavior". I just started writing the code,
this
will be the "fun" part. It is going to be a XMAS present for my son, working

like crazy to get it done in time. Talk about a DEADLINE ................

Once everything is finished I will put all the info on my webpage. Until
then,
I hope this helps!!

Best regards,
Steven


Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

"Great spirits have always encountered violent
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2000\12\07@142451 by Dan Michaels

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Henry Low wrote:
.......
>hi Michaels,
>    I have been surfing the net for similar robotic applications using the
>PIC16F877 but I just could not find any useful materials.


Yes, I have searched the web a lot voer the past several weeks myself,
and found that the vast majority of available boards use the 68HC11
processor, no doubt stemming from those originally developed at MIT
- course 6.270. There appear to be few PIC-based boards available
- so being a PIC enthusiast, I decided to produce my own :).

Being a "premier" hacker, I have put up a lot of links dealing
especially with robo-hacking on my site, including links to 68HC11
controller boards/etc:

http://www.oricomtech.com/emerge5.htm#Hobby2
================

My robot is really
>simple, its sole objective is obstacle avoidance and being able to move
>around the room without getting stuck. After I have achieved that, I might
>add on a mapping feature to it or a "seeking warmest object task".
>Anyway, why did u ask "Finding the '877 adequate to the task?", isn't 877
>quite sufficient for my application?? It has got PWM output, and sufficient
>I/O lines for me i think.


I just asking since I wasn't too sure how far along the project you were
[and also fishing for some MotHC11 user to comment]. And yes, I think
the '877 chips have plenty of capability for this type of project.
================

Actually, I am a real newbie in programming this
>chip, in fact this is my first time working with microcontroller. I wonder
>if source code of other PIC chips are useable for 877?? I hope to get some
>relevant source code of similar nature (like motor control, sensor
>interface) for reference so that I may pick up the fun faster.
>    Hope to hear from you soon.
>

Yes, all of the 2nd generation-PIC source is pretty much interchangeable
between processors - although you do have to take into account the
different pinouts and memory mapping as the chip resources grow.

I haven't written any source for this project yet, but am currently
working on design of a pcb that will include motor control, IR and
ultrasonic sensors, general digital I/O, 40-pin PIC, etc. It will
be a small board with L293D chips for direct control of a couple
of small motors.

best regards,
- Dan Michaels
==============

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2000\12\07@155915 by Robert C. Gates

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I would like to find out what you are using for drive train and track.  I
have been looking for a suitable platform but have been cursed with wanting
to do it as small as possible.  Any input would be appreciated.

Thanks,

Rob

{Original Message removed}

2000\12\07@165656 by rchock, Steve

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Rob:

I am using 2 "Tracked Vehicle Chasis" from TAMIYA (http://www.tamiya.com/).
as the mobile platform. I found a better hackable one at http://www.robotstore.com

3-354 - Bulldozer Kit - $37.95

Or you can buy just the motor:

3-709 - Twin Motor Gear Box Kit - $19.95

The tread on the kit I am using can be made small or large (connect
together).
This way I could make the kit very small, depending on what I want. I hope
this helps.

Best regards,
Steve

Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

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oppposition from mediocre minds."--A.Einstein

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2000\12\07@173025 by Dan Michaels

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Robert Gates wrote:
>I would like to find out what you are using for drive train and track.  I
>have been looking for a suitable platform but have been cursed with wanting
>to do it as small as possible.  Any input would be appreciated.
>

Rob, to answer your question for Steve [as if it were intended for
me - he, he], I am planning to use the Tamiya dual-motor geartrain,
about $15. I believe it is the same as used in some of the hobby
tanks for sale - possibly Radio Shack's:

http://www.sinerobotics.com/twinmotor.html

The Tamiya site has a list of states with local dealers. Several
carry this motor in my area:

http://www.tamiya.com/america/ta.htm

- danM

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2000\12\07@220734 by Dan Michaels

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Steven Kosmerchock wrote:
>Rob:
>
>I am using 2 "Tracked Vehicle Chasis" from TAMIYA (http://www.tamiya.com/).
>as the mobile platform. I found a better hackable one at http://www.robotstore.com
>
>3-354 - Bulldozer Kit - $37.95
>
>Or you can buy just the motor:
>
>3-709 - Twin Motor Gear Box Kit - $19.95
>

Hi Steve, as you are using the exact motor system I have been
planning to buy, and as they never seem to publish the info I
want, can you tell me about how much current the motors draw in
various loading situations?

I want to use the L293D H-bridge chips, which are rated for 600mA
tops [ie, with good heat sinking]. Did you need to use an H-bridge
rated greater than this?

thanks,
- dan michaels
==============

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2000\12\07@234718 by Tom Handley

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  Steve, Dan and I are also building PIC-based robots and have looked at
the TAMIYA gearbox. My main concerns with using it is the torque and the
ability to hack a tach onto each motor. Right now I'm hacking a Radio SHack
R/C car and replaced the motor with decent results but it's just a test-bed
until I build a decent platform with dual motors. I've tested both optical
and Hall-Effect sensors for the tach with the latter using a fraction of the
current of optical versions. I used 1/8" rare-earth magnets from Radio
Shack. The problem is that it requires more space than an optical wheel.
Anyway, can you give us a rough idea how powerful that gearbox/motor set is
in it's lowest gear ratio? I'm looking at a platform at least 8" long and
6-8" wide. I'm also favoring sealed lead-acid batteries over nicads so there
will be some weight there.

  As far as IR sensors, I lost the link but there's a simple design using a
PIC12C508, two IR LEDs pointing front-left and right, and a typical Sharp IR
receiver. You can adjust the sensitivity via software by changing the
modulation frequency. The code is trivial and can be used with any PIC.
Also, look into simple bumper switches which will tell you when you actually
hit something. There are dozens of ways to make them. Check the following
links which should point the way to the IR receiver:

     Portland Area Robotics Society
     http://www.rdrop.com/~marvin/

     Seattle Area Robotics Society
     http://www.seattlerobotics.org/

     Robotics Magazine
     http://www.robotmag.com/default.htm

  - Tom

At 04:54 PM 12/7/00 -0500, Steve Kosmerchock wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\08@003303 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

Dan, there are two very cheap, common and good motor driver
chips, the BA6209 and BA6219. These are the same size as
L293 and are good for 1.2A and 2.0A respectively. We use them
all the time in VCRs. They have direction/speed control with
two input pins. Speed control is analogue. They are about
$1.50 to $2 US if you shop around.

I have full datasheets if you are interested, or you can get
datasheets at
http://www.rohm.com/products/databook/motor/pdf/

These are a great cheap little chip.
:o)
-Roman

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2000\12\08@010037 by Dan Michaels

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Tom Handley wrote:
>   Steve, Dan and I are also building PIC-based robots and have looked at
>the TAMIYA gearbox. My main concerns with using it is the torque and the
>ability to hack a tach onto each motor.


Hello again, Tom,

I was wondering if you were still going this route, or whether the
flame had sputtered. Well, you're building, I'm still dreaming, in
betweenst <-- :) --> all the other projects. I am however designing
my own botboard based upon a PIC74/77, and hope to send away for pcbs
in a week or so. Most available boards use the 68HC11 chips.
Preliminary info:

http://www.oricomtech.com/projects.htm

I have been researching various motor options and plan to use the
Tamiya twin-motor set on my initial effort. Not wanting to do a lot
of mechanical fabs, I plan to build it using a couple of "spare"
AOL CDROMs for the body. I figure 9 drilled holes will do the whole
thing.

Once I know a little more about motor current reqs, I can design
the motor drive on my SBC. Hopefully the L293D chip @ 600 mA will
handle the small motors for a small bot - but probably not for a
larger one.
====================

.............>
>   As far as IR sensors, I lost the link but there's a simple design using a
>PIC12C508, two IR LEDs pointing front-left and right, and a typical Sharp IR
>receiver. You can adjust the sensitivity via software by changing the
>modulation frequency.


I put up a lot of robo-hack links on my page, with special emphasis
to sites with motor control and IR sensor stuff. There are also some
ultrasonic sensor systems and cool bat detectors. K.Leang has some
good all-around info.

http://www.oricomtech.com/emerge5.htm#Hobby2
http://www.leang.com/robotics/info/roboinfo.html

best regards,
- Dan Michaels
Oricom Technologies
===================

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2000\12\08@050458 by Simon Nield

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tom:
>and Hall-Effect sensors for the tach with the latter using a fraction of the
>current of optical versions. I used 1/8" rare-earth magnets from Radio
>Shack. The problem is that it requires more space than an optical wheel.


just curious about this tom, but how have you assembled your magnetic sensor ?
i always assumed that the way this would be done would be to have a hall sensor pointing at the edge
of a metal gear, with a small permanent magnet the other side of the sensor from the gear... is this
how it works or do you have the magnet fixed to the rotating parts, a little like a digital odometer
for a bicycle ?

regards,
Simon

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2000\12\08@124456 by Dan Michaels

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Roman Black wrote:

>Dan, there are two very cheap, common and good motor driver
>chips, the BA6209 and BA6219. These are the same size as
>L293 and are good for 1.2A and 2.0A respectively. We use them
>all the time in VCRs. They have direction/speed control with
>two input pins. Speed control is analogue. They are about
>$1.50 to $2 US if you shop around.
>
>I have full datasheets if you are interested, or you can get
>datasheets at
>http://www.rohm.com/products/databook/motor/pdf/
>
>These are a great cheap little chip.


Thanks Roman, I'll check these chips out. Probably need
a big heat sink and external clamping diodes, I would imagine.

How much trouble have you seen with motor noise getting back
through this kind of chip to the uC pins? I imagine the problem
is worse at the higher currents. Are you using any specific
filters to deal with this? I was thinking it might be good idea
to put RC filters between PIC and the L293 control pins to be safe.

- danM

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2000\12\08@230513 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

Dan, I haven't used these in a project but I work with them
all the time in VCRs. They usually drive a small motor about
200mA with no heatsinking (just the built in tag on the chip)
and they don't get that warm. I have seen them used to drive
much larger motors in older VCRs with a small heatsink. As
they are a flatpack heatsinking is easy, you can even bolt
them to the case.

The datasheet recommends that they be used with a series
resistor to the power rail and a large filter cap close to
the power pin of the chip. I think this would kill a lot
of the noise. It is always a good idea to put a cap across
the dc motor pins on the motor and a snubber at the chip
across the motor connections. I wouldn't expect these chips
to make the RF that a L293 makes. By the way, the L298 is
a 2A version of the L293 (1A).

-Roman

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2000\12\09@080457 by Duane Brantley

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Does anyone make a bridge that will handle, say, in the order of 15 - 20
amps peak (stall)?  I haven't done a full load test on the gear head motors
that I'm going to use, but I know they can easily pull 12 Amps.

Happy Holidays,

Duane

{Original Message removed}

2000\12\09@125225 by Dan Michaels

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Duane Brantley wrote:
>Does anyone make a bridge that will handle, say, in the order of 15 - 20
>amps peak (stall)?  I haven't done a full load test on the gear head motors
>that I'm going to use, but I know they can easily pull 12 Amps.
>

I have a feeling that Duane Brantley makes this type of
a circuit.

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2000\12\09@132701 by Dan Michaels

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Tom Handley wrote:
>   Steve, Dan and I are also building PIC-based robots and have looked at
>the TAMIYA gearbox. My main concerns with using it is the torque and the
>ability to hack a tach onto each motor. Right now I'm hacking a Radio SHack
>R/C car and replaced the motor with decent results but it's just a test-bed
>until I build a decent platform with dual motors.
................


Hi Tom,

Got some follow-up info --> good stuff available NO-wheres else that
I could ever find. Went down and got the Tamiya twin-motor gear-train
[$11.50 at one of the local hobby shops]. They use the "130" motors,
apparently identical to the bantam weight FA130RA2270 shown in the
Jameco catalog. Spec'ed at 1.5-3v, 200mA, 9100RPM, $0.99.

Set it up for the slower 203:1 gearing, uses 4 gearsets with about
4:1 reduction each. It is actually quite torque-y, and hard to stall
by squeezing the output shaft. You cannot move the motor shaft by
trying to hand-turn the final "gear".

Runs well at ~2.0v on the motor, drawing ~500mA @ 48RPM output
--> motor doing about 9700RPM. 3v on the motor is a little much,
drawing ~1000mA.

All in all, looks pretty good for my first project, using "free" AOL
CDROMs for the body, and running off a couple of L293D H-bridges
and 3-4 AA's. Got enough info now to go ahead and design my new SBC.

Ever get your car to run "slow" enough?

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\09@161623 by Duane Brantley

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I'm beginning to think he does to....

-----Original Message-----
From: Dan Michaels [spamBeGoneoricomspamBeGonespamUSWEST.NET]
Sent: Saturday, December 09, 2000 11:52 AM
To: TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
Subject: Re: [OT]: Robotics with PIC16F877 anyone??


Duane Brantley wrote:
>Does anyone make a bridge that will handle, say, in the order of 15 - 20
>amps peak (stall)?  I haven't done a full load test on the gear head motors
>that I'm going to use, but I know they can easily pull 12 Amps.
>

I have a feeling that Duane Brantley makes this type of
a circuit.

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2000\12\10@010702 by dre Domingos F. Souza

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>Got some follow-up info --> good stuff available NO-wheres else that
>I could ever find. Went down and got the Tamiya twin-motor gear-train
>[$11.50 at one of the local hobby shops]. They use the "130" motors,
>apparently identical to the bantam weight FA130RA2270 shown in the
>Jameco catalog. Spec'ed at 1.5-3v, 200mA, 9100RPM, $0.99.

       Where can I find it? No local hobby shops uses to sell tamya merchandise!


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       RemoveMExandinhospamTakeThisOuTinterlink.com.br
       Linux User #85093

--------------8<-------Corte aqui-------8<--------------

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2000\12\10@052910 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

Hi Dan, use some light machine oil on the bronze motor bearings,
will extend motor life a lot. Also see if you can get some
"super-grease" for the multiple gear gearbox, it will make it
quieter and reduce wear. This super sticky grease will even
help a bit with backlash. If you can enclose around the gears
with anything this is even better, just fill it with a couple
cc's of grease. You can get good long term results from these toy
motors with some professional lubing.
-Roman

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2000\12\10@140624 by Dan Michaels

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Roman Black wrote:
>
>Hi Dan, use some light machine oil on the bronze motor bearings,
>will extend motor life a lot. Also see if you can get some
>"super-grease" for the multiple gear gearbox, it will make it
>quieter and reduce wear. This super sticky grease will even
>help a bit with backlash. If you can enclose around the gears
>with anything this is even better, just fill it with a couple
>cc's of grease. You can get good long term results from these toy
>motors with some professional lubing.
>-Roman
>

Tamiya includes some grease with the geartrain. Haven't used
it yet. Don't know how super it is. So far tried w/o same, and
very noisy. The way the cage is built, it would be quite easy
to enclose. All in all, the Tamiya dual-motor is a nice system
for the price.

best regards,
- Dan Michaels
===============

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2000\12\10@140633 by Dan Michaels

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Roman Black wrote:
>>
..........
>The datasheet recommends that they be used with a series
>resistor to the power rail and a large filter cap close to
>the power pin of the chip. I think this would kill a lot
>of the noise. It is always a good idea to put a cap across
>the dc motor pins on the motor and a snubber at the chip
>across the motor connections. I wouldn't expect these chips
>to make the RF that a L293 makes. By the way, the L298 is
>a 2A version of the L293 (1A).
>


Roman, thanks for the info. I'll breadboard the L293D to Tamiya
motor/geartrain to the PIC this week, and see what kind of
noise I get. And how hot the L293's run.

The L298's would probably be better, but not as convenient
for a small pcb. Seems to me, however, for high power, if you
simply run the 4 outputs of the L293 out separately, rather
than tying them together 2-by-2, you could directly drive an
external H-bridge made up of nothing more than 2 hi-current
PMOSFETs and 2 hi-current NMOSFETs. The L293's can handle
the hi-voltages, and PWMing its outputs should work with the
2nd H-bridge.

At least this is my perception. And maybe a more flexible
route than worrying about putting a high-current H-bridge
on the small pcb from the get-go.

best regards,
- Dan Michaels
==============

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2000\12\10@140635 by Dan Michaels

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Alexandre Souza wrote:
>>Got some follow-up info --> good stuff available NO-wheres else that
>>I could ever find. Went down and got the Tamiya twin-motor gear-train
>>[$11.50 at one of the local hobby shops]. They use the "130" motors,
>>apparently identical to the bantam weight FA130RA2270 shown in the
>>Jameco catalog. Spec'ed at 1.5-3v, 200mA, 9100RPM, $0.99.
>
>        Where can I find it? No local hobby shops uses to sell tamya
merchandise!
>

Check the websites. Tamiya has a list of dealers in the US by state,
maybe for other countries. The 130 motor is Jameco P/N 166676, but
Jameco does NOT sell the twin-motor geartrain.

http://www.tamiya.com
http://www.jameco.com

- danM

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2000\12\10@154046 by Bob Blick

face
flavicon
face
get it at http://www.towerhobbies.com. They also have a neat tracked vehicle
chassis kit. The search function works, but the part numbers are:

Tower#   Tamiya#
LXHA15   70097 TWIN MOTOR GEAR BOX 10.59
LXGZ87   70108 TRCKD VEHICLE CHASSIS KT 15.19

Cheers,

Bob

At 02:06 PM 12/10/2000 -0500, you wrote:
{Quote hidden}

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2000\12\10@155059 by Dan Michaels

flavicon
face
Bob Blick wrote:
>get it at http://www.towerhobbies.com. They also have a neat tracked vehicle
>chassis kit. The search function works, but the part numbers are:
>
>Tower#   Tamiya#
>LXHA15   70097 TWIN MOTOR GEAR BOX 10.59
>LXGZ87   70108 TRCKD VEHICLE CHASSIS KT 15.19
>

There are also 2 other Tamiya tracked chassis -[note - HWVTech shipping
costs to US are prohibitive].

http://www.hvwtech.com/gearsets.htm

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2000\12\10@184128 by Mitchell D. Miller

picon face
Who makes the L293 and 298?  Ie: Where can I find data sheets?

-- Mitch

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2000\12\10@190713 by dre Domingos F. Souza

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>Who makes the L293 and 298?  Ie: Where can I find data sheets?

       ST comes to mind...


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       xandinhoEraseMEspam.....interlink.com.br
       Linux User #85093

--------------8<-------Corte aqui-------8<--------------

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2000\12\10@210954 by Dan Michaels

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Mitchell D. Miller wrote:
>Who makes the L293 and 298?  Ie: Where can I find data sheets?
>

ST and Unitrode. Also, TI has same pinout - SN754410.

http://www.us.st.com/stonline/products/selector/58.htm

I have some links to boards [Handyboard ....] and ckts using them:

http://www.oricomtech.com/emerge5.htm#Hobby2

Also, Roman gave a link other day to Rohm H-bridge chips.

- dan michaels

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2000\12\11@000751 by Tom Handley

picon face
  Simon, in my `hack' I glued two 1/8" rare-earth magnets on opposite sides
of a gear shaft on the motor. Normally, I would mount several around a disk
for this application. I'm using Panasonic DN6852As available from Digi-Key.
These are unidirectional with all the signal conditioning in the sensor. The
output is open-collector. The package is a small 3-lead SIP. It operates
from 3.6 to 16V with a supply current of around 5.5ma.

  - Tom

At 10:02 AM 12/8/00 +0000, Simon Nield wrote:
>tom:
>>and Hall-Effect sensors for the tach with the latter using a fraction of the
>>current of optical versions. I used 1/8" rare-earth magnets from Radio
>>Shack. The problem is that it requires more space than an optical wheel.
>
>
>just curious about this tom, but how have you assembled your magnetic
sensor ?
>i always assumed that the way this would be done would be to have a hall
sensor pointing at the edge
>of a metal gear, with a small permanent magnet the other side of the
sensor from the gear... is this
>how it works or do you have the magnet fixed to the rotating parts, a
little like a digital odometer
>for a bicycle ?
>
>regards,
>Simon


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\11@000759 by Tom Handley

picon face
  Dan, well I'm working on it in spare time but I really want to wait for a
dual motor platform instead of spending much more time on this R/C car. I've
got various things bolted onto it for testing. I finally hacked an RC servo
to control the steering but I have not done much code for a crude AI. Right
now the speed control works and if it bumps into something, it backs up,
turns for a second or two, and tries again. There's not much else to do with
a typical car chassis other than using the IR sensor (or Ultrasonic) to
detect objects and try to avoid them. If there is no path inbetween, then
stop and backup again. I'm running the car in reverse to provide front-wheel
drive and rear-wheel steering but two motors with an idler wheel are the way
to go for my application.

  I noticed Roman mentioned the BA6209/6219. When I tore apart an old VCR
looking for motors and gears, I found a BA6209 and could'nt find anything on
the chip. I had forgot about R-Ohm. (Thanks Roman!). I want to take a look
at those chips.

  I'm using multiprocessing with a 16F876 for testing, 12C508 for the IR
detector, 12C671 as a dual RC servo controller (I needed the TMR0
interrupt), and a 16F84 as a dual H-Bridge controller. I plan on another
12C508 for the Ultrasonic detector. They all talk over a serial interface.
The whole idea is to keep it modular with a standard interface so I can
easily add or remove modules (kind of like Leggo's system). The 16F876's
Port B goes to a standard 74x30 8-Input NAND gate used to expand the
interrupts to 7 channels with the output going to RB0/INT. Since I'm
planning on adding other goodies such as a Vector 2X compass, I'll
definitely be using a 16F877. If I can just pin down the platform... I'm
real interested to hear your experiences with that TAMIYA gearbox!

  The CDROM's are a good idea. I save them for coasters ;-) You know, they
might make good wheels if you could find a way to add a rubber O-ring or
something around the edge. Maybe glue 2-3 CDs together. You could easily
drill holes or mount magnets on them to count revoloutions. It would'nt be
practical for a tach but you could sense how far you traveled. I haven't got
that far yet on my hack.

  - Tom

At 01:00 AM 12/8/00 -0500, Dan Michaels wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\11@002127 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

Cool. Shame Tamiya is so expensive here in Aust. :o(
-Roman

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2000\12\11@004033 by David Duffy

flavicon
face
>Roman Black wrote:
>Cool. Shame Tamiya is so expensive here in Aust. :o(
>-Roman

I've been following this thread with interest as my son is keen
(OK, me too !) to make something that zips about the room.
I have a pile of used CD spindle motors,etc and a couple of
steppers from 5.25" drives. Is it worth trying to use the stepper
motors as 1:1 direct drive? (wheel on motor shaft) I suspect
that there may not be enough torque to drive it along. I was
thinking of a platform about 150mm (6") x 200mm (8") made
from 2mm (3mm?) sheet aluminium. The biggest problem is
making it carry around the battery pack & all the other bits
that will probably get tacked on as the project progresses.
Jaycar have some motors & a gearbox that I've ordered to
play around with. Looks like a never ending kind of project!
Regards...

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2000\12\11@011615 by Roman Black

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face
David Duffy wrote:
>
> >Roman Black wrote:
> >Cool. Shame Tamiya is so expensive here in Aust. :o(
> >-Roman
>
> I've been following this thread with interest as my son is keen
> (OK, me too !) to make something that zips about the room.
> I have a pile of used CD spindle motors,etc and a couple of
> steppers from 5.25" drives. Is it worth trying to use the stepper
> motors as 1:1 direct drive? (wheel on motor shaft) I suspect
> that there may not be enough torque to drive it along. I was
> thinking of a platform about 150mm (6") x 200mm (8") made
> from 2mm (3mm?) sheet aluminium. The biggest problem is
> making it carry around the battery pack & all the other bits
> that will probably get tacked on as the project progresses.
> Jaycar have some motors & a gearbox that I've ordered to
> play around with. Looks like a never ending kind of project!
> Regards...

David, ask around for an old fax or check local garage sales
and flea markets. You can get old faxes for a couple of bucks
or even free. They usually have two matched motors with small
simple gearboxes attached, about 7:1 is typical. There are
also rubber rollers that you can cut into wheels and tyres.
I have a little desk robot made from two of these motors,
only problem you need about 16v to get decent torque so you
need a few NiCds, my little robot positions in about 0.25mm
steps, and makes the coolest mechanical whine from the
steppers, just like a real robot. I drive the motors with
ULN2003 chips.

If you want to use your own steppers, check dick smith
stores, (also altronics/jaycar) they have small plastic
gear sets and stuff for hobby robot use. :o)
-Roman

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2000\12\11@015607 by Roman Black

flavicon
face
Duane Brantley wrote:
>
> Does anyone make a bridge that will handle, say, in the order of 15 - 20
> amps peak (stall)?  I haven't done a full load test on the gear head motors
> that I'm going to use, but I know they can easily pull 12 Amps.
>
> Happy Holidays,
>
> Duane


Hi Duane, do you have a solution for this? I often need
high power drivers and usually design from scratch.

The main problem with high power h-bridge chips is the
barbaric saturation voltages. They try and sell a chip
as a 2amp h-bridge when it has 4v saturation at 1A!!
This disgusts me, I build h-bridges from junk bipolar
transistors I find lying around, with 0.2v sat per device
even that is only 0.4v total saturation. It's disgusting
that a high-tech h-bridge chip has 10 times worse
performance than something I built from junk.

Now if you can tell me about a 2A to 10A h-bridge with
good sat voltage I would be *very* happy!! I have been
looking for something like this for a long time. :o)
-Roman

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2000\12\11@080016 by rchock, Steve

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face
Dan:

Looking at the motors, they were drawing about 400mA (MAX) EA continous.
Not sure of the exact amount,... doing this from memory after 3 days off.
My robot is at home, but I can check tonight, and let you know tomorrow.

Steve


Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

"Great spirits have always encountered violent oppposition from mediocre
minds."--A.Einstein

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2000\12\11@080227 by rchock, Steve

flavicon
face
Tom:

I check tonight and let you know how much my robot weighs and
the dimensions. My robot weighs at least a couple of pounds, seems
to go pretty fast. I will let you know tomorrow.

Steve

Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

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2000\12\11@081712 by rchock, Steve

flavicon
face
Dan:

Great to hear that it will be working for you.
The price of those TAMIYA kits are well worth what you get.

Steve

--

Hi Tom,

Got some follow-up info --> good stuff available NO-wheres else that
I could ever find. Went down and got the Tamiya twin-motor gear-train
[$11.50 at one of the local hobby shops]. They use the "130" motors,
apparently identical to the bantam weight FA130RA2270 shown in the
Jameco catalog. Spec'ed at 1.5-3v, 200mA, 9100RPM, $0.99.

Set it up for the slower 203:1 gearing, uses 4 gearsets with about
4:1 reduction each. It is actually quite torque-y, and hard to stall
by squeezing the output shaft. You cannot move the motor shaft by
trying to hand-turn the final "gear".

Runs well at ~2.0v on the motor, drawing ~500mA @ 48RPM output
--> motor doing about 9700RPM. 3v on the motor is a little much,
drawing ~1000mA.

All in all, looks pretty good for my first project, using "free" AOL
CDROMs for the body, and running off a couple of L293D H-bridges
and 3-4 AA's. Got enough info now to go ahead and design my new SBC.

Ever get your car to run "slow" enough?

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\11@090848 by Henry Low

flavicon
face
hey guys, I tot this was suppose to be a thread abt the PIC16F877?? hahahah
It's ok though, just that I always thought that help is coming until I read
the full mail.....

{Original Message removed}

2000\12\11@100651 by Roman Black

flavicon
face
Sorry Henry, just to answer your question I do think the
F877 is an *excellent* chip to run a small robot. I bought
a few just for that purpose. If you post a specific question
re the robot you are building I'm sure that either I can help,
or the really smart PIC people here can help.

I think many people here are pretty comfortable with making
our PICs do whatever we want so the topics turn to the things
we attach to our PICs, hope that makes sense. :o)
-Roman




Henry Low wrote:
>
> hey guys, I tot this was suppose to be a thread abt the PIC16F877?? hahahah
> It's ok though, just that I always thought that help is coming until I read
> the full mail.....
>
> {Original Message removed}

2000\12\11@101719 by Henry Low

flavicon
face
yeah.....finally....I did post one before...but only a few replied....
anyway, I just want to use a single PIC chip (16F877) to control an
autonomous wheeled robot. So the I/Os here will only be the sensors input
and output control to drive the motor.
Very possibly I will also buy those ready-made expensive wheel encoders for
my speed feedback so I will need to have velocity control of both motors
(one motor for each wheel, my robot is only 2 wheel-drive). I would want to
make sure I know how to use the encoders before I buy them. (I need 2 for
the 2 motors). I know I will need a quadrature decoder but the details I am
not sure....furthermore, I am also not sure how to bring out PWM output from
this PIC and how to adjust the duty cycle. Can I use PWM to vary the
direction of the motor rotation??

Regards,
Henry

{Original Message removed}

2000\12\11@113732 by Dan Michaels

flavicon
face
David Duffy wrote:

Is it worth trying to use the stepper
>motors as 1:1 direct drive? (wheel on motor shaft) I suspect
>that there may not be enough torque to drive it along.

David,

If you are wondering about torque, try firing up the stepper
and seeing how difficult it is to stall it by squeezing the
shaft. As I mentioned last time, with the little Tamiya drive
set for 200:1 reduction, I have to exert quite a bit of force
to slow down the motor. Difficult to stall. And I cannot even
budge the motor by trying to turn the final gear [not the shaft].

A very common robo-hack is to take model airplane servo motors, eg
S-148 and HS300, and convert them for full rotation. Apparently,
they have enuf torque for minibots. However, even the cheapo
servos are expensive, $15 min apiece. I have some links to
servo and stepper motor robohacking:

http://www.oricomtech.com/emerge5.htm#Hobby2

best regards,
- Dan Michaels
Oricom Technologies
===================

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2000\12\11@122937 by Dan Larson

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On Sun, 10 Dec 2000 22:13:05 -0200, Alexandre Domingos F. Souza wrote:

>>Who makes the L293 and 298?  Ie: Where can I find data sheets?
>
>        ST comes to mind...
>
>

And Mouser is one place that sells them.  The L293D is $2.00 Qty 1.

Dan

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2000\12\11@124201 by Bob Blick

face
flavicon
face
> >>Who makes the L293 and 298?  Ie: Where can I find data sheets?
> >
> >        ST comes to mind...
> >
> And Mouser is one place that sells them.  The L293D is $2.00 Qty 1.

Remember that the L293D consumes 80 milliamps when idling. In a robot that
spends a lot of time not moving, this can kill your batteries in a hurry.

Bridges made by Rohm, and also my design, do not have this problem, draw
nothing when idle:

http://www.bobblick.com/bob/projects/hbridge/index.html

Cheerful regards,

Bob Blick

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2000\12\11@131104 by Dan Michaels

flavicon
face
Henry Low wrote:
>hey guys, I tot this was suppose to be a thread abt the PIC16F877??
.............


To inject some PIC back into this thread ..... here is a rough
sketch of my PICoBotboard plans:

- modify my existing PIC40 SBC for use as a botboard. This board can
 use '74/77/etc:

    http://www.oricomtech.com/sbc40.htm

- new layout - remove SRAM and add cktry for motor control, plus
 sound, IR, ultrasonic, and bumper sensors:

         --------+       bank of 8 uncommitted LEDs + series-Rs
                 |
                 |  1 A/D
                 |<---/-- 4-input R-divider [input from bumper sw,
                 |                       output to PIC A/D channel]
                 | 2 DI/O
                 |<---/--> IR LED + QSE156QT optologic detector
           PIC40 |
                 |  2 A/D
                 |<---/--- LM324 [4 opamps - setup as 2-stage hi-gain AC-
                 |            coupled amps for mike and ultrasonic rcvr]
                 | 10 DI/O
                 |---/----> L293D [2 ea - setup as H-bridges]
                 |   2 PWM [motor speed - to enable inputs]
         --------+   8 DI/O [control signal inputs]

- LEDs can be jumpered to provide visual indication of subsystem operation.

- The L293D chips can be setup as 2 H-bridges to drive the Tamiya
 twin-motors. For other apps, the channels can be separated to drive
 up to 8 individual motors.

- Still working out sensor details. For IR object detector, can
 drive IR LED directly off PIC pin at 20-40Khz, and pickup using a
 QSE156QT optologic sensor --> straight to PIC. This sensor could
 also pickup up signals from a TV remote or Palm.

- For long-range ultrasonics, I have a transducer set from Jameco, but
 minimal spec data is available [Jameco doesn't even know the name of
 the maufacturer!!]. However, plan to use BJT inverter to drive xmtr,
 and run rcvr --> 1st LM324 2-stage amp --> integrator --> PIC A/D.

- For sound pickup, electret --> 2nd LM324 2-stage amp --> PIC A/D.

- For bumpers, 4 microswitches --> 4-input R-divider --> PIC A/D.

I figure I can squeeze this all onto my SBC40 form-factor, 2.5"x3.6",
and still have plenty of pins left over for RS-232, an I2C serial
EEPROM chip, up to 5 more A/D channels, and up to 6-8 digital I/O
channels.

so much for now,
- Dan Michaels
Oricom Technologies
===================

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2000\12\11@141924 by Dan Michaels

flavicon
face
Bob Blick wrote:
>Remember that the L293D consumes 80 milliamps when idling. In a robot that
>spends a lot of time not moving, this can kill your batteries in a hurry.
>

Good point - this might kill my project too - hadn't gotten to
breadboarding it yet. No wonder those MIT Handyboards with the L293's
have a hi-current battery charger built right in :o).
=============

>Bridges made by Rohm, and also my design, do not have this problem, draw
>nothing when idle:
>
>http://www.bobblick.com/bob/projects/hbridge/index.html

You've got some nice hot [big, not smoky] motors there too.

- danM

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2000\12\11@144045 by Dan Michaels

flavicon
face
Bob Blick wrote:
>
>http://www.bobblick.com/bob/projects/hbridge/index.html


Bob, I was looking at your H-bridge and you mention that
separate free-wheeling diodes are not required since the TIP
transistors have diodes internally. Are these really robust enough
to handle the inductive surges?

BTW, it looks like your ckt could almost handle the currents
Duane Brantley is requiring. Can you possibly parallel the
TIP's to get more drive? Tried power MOSFETs?

thanks,
- dan michaels
==============

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2000\12\11@161654 by Bob Blick

face
flavicon
face
> >www.bobblick.com/bob/projects/hbridge/index.html
> > Bob, I was looking at your H-bridge and you mention that
> separate free-wheeling diodes are not required since the TIP
> transistors have diodes internally. Are these really robust enough
> to handle the inductive surges?

Yes, the internal diodes are rated for full current. The circuit is very
inexpensive and relatively simple because of this.

> BTW, it looks like your ckt could almost handle the currents
> Duane Brantley is requiring. Can you possibly parallel the
> TIP's to get more drive? Tried power MOSFETs?

You can use TIP14x instead of TIP12x and have double the ratings. The
drawback is that these are Darlington transistors and produce a bit of
heat.

Someday when I get inspired I'll do a circuit with MOSFETs and also put
current limiting in it, but MOSFETs really add to the complexity unless
you use P-Channel MOSFETs in the upper rail, which I am loathe to do as I
am a cheapskate.

Cheers,

Bob

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2000\12\11@192448 by Byron A Jeff

face picon face
>
> Bob Blick wrote:
> >
> >http://www.bobblick.com/bob/projects/hbridge/index.html
>
>
> Bob, I was looking at your H-bridge and you mention that
> separate free-wheeling diodes are not required since the TIP
> transistors have diodes internally. Are these really robust enough
> to handle the inductive surges?
>
> BTW, it looks like your ckt could almost handle the currents
> Duane Brantley is requiring. Can you possibly parallel the
> TIP's to get more drive? Tried power MOSFETs?

Probably easier to just get bigger TIPs. the TIP14X series handles twice
the current of the TIP12X series. You can then go up to 10 amps.

BAJ

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2000\12\11@221805 by Dan Michaels

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Tom Handley wrote:
>   Dan, well I'm working on it in spare time but I really want to wait for a
>dual motor platform instead of spending much more time on this R/C car.

Still interested in that Radio Shack tank? I wonder if it has the
Tamiya twin-motor in it. [you could buy one and tell me].
===============

>   I'm using multiprocessing with a 16F876 for testing, 12C508 for the IR
>detector, 12C671 as a dual RC servo controller (I needed the TMR0
>interrupt), and a 16F84 as a dual H-Bridge controller. I plan on another
>12C508 for the Ultrasonic detector. They all talk over a serial interface.

You connecting all the chips to the same RS-232 channel? How are you
doing this? Ever think of using just a single PIC40 for the whole
thing? But, I guess, servo control would be a problem if you have to
keep feeding signals to it.
===============


>The whole idea is to keep it modular with a standard interface so I can
>easily add or remove modules (kind of like Leggo's system).

I'm thinking along the same lines, but with several stacked PIC40
boards. Lowest one would do most of low-level processing, as I
described earlier in the day. Next one up would have a 32KB SRAM
and be used to store real-time "mapping" data obtained by the
low-level board as the beastie runs around the room. Basically
build up an internal representation of the environment - would
need some kind of external landmarks for this - IR beacons or
something.
=====================

 The 16F876's
>Port B goes to a standard 74x30 8-Input NAND gate used to expand the
>interrupts to 7 channels with the output going to RB0/INT.

Why do you need all these interrupts? I figure my thing wouldn't
be moving very fast, so I can poll the sensor ports. Also, with the
L293 chips controlled by dedicated I/O pins and the 2 PWM channels
used for speed control, it wouldn't require any processor cycles
for real-time control over the motors.

The bot will either run very slowly or else run a few inches, and
stop and take sensor readings. Slow-lane robotics here.
===============

Since I'm
>planning on adding other goodies such as a Vector 2X compass, I'll
>definitely be using a 16F877. If I can just pin down the platform... I'm
>real interested to hear your experiences with that TAMIYA gearbox!
>

Maybe GPS, too?  BTW, the latest/greatest GPS apps I have heard
about are: a) herding cows, and b) finding free spots in parking
lots. a) works by "cow whispering", b) works by having a satellite
photograph the parking lot from space, and downloading a map
to the computer in your Cadillac SUV. A traveling salesman
algorithm routes you to the open space before any other cars
can get to it - Cadillacs rule [what a gas].

Re Tamiya, will breadboard a PIC, L293 and Tamiya together
this week. Look for possible motor noise/heating/etc problems.
===================

>   The CDROM's are a good idea. I save them for coasters ;-) You know, they
>might make good wheels if you could find a way to add a rubber O-ring or
>something around the edge. Maybe glue 2-3 CDs together. You could easily
>drill holes or mount magnets on them to count revoloutions. It would'nt be
>practical for a tach but you could sense how far you traveled. I haven't got
>that far yet on my hack.
>

Nice thing, for a botbody, you can stack any #of AOL disks [I
must have millions] till you have it as rigid as you want. For
wheels, CDs are too big, I think. I bought some 1.75" rubber
airplane wheels for the Tamiya. Friction, plus small size for
good torque.

Also, with CDs, you can easily build a multi-level bot.

For distance measurements, I'll probably just relie on
"no"-slippage initially.
=============

BTW, Walgreens is advertising 3 little RC cars for $12
altogether. Heckuva deal for radio links - if can get different
frequencies. This way one xmtr-rcvr in bot, another in
base station --> 2-way comm. Slow, but that's probably ok
if the bot has some minimal brains.

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
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2000\12\11@222829 by Dan Michaels

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Steve Kosmerchock wrote:

>Great to hear that it will be working for you.
>The price of those TAMIYA kits are well worth what you get.
>

Hi Steve,

Tom's worried about the torque on this lashup, but looking
at the internals of an older Tamiya tank, I see they did not
use the geartrain I bought, but one that is clearly geared
much higher:

   http://www.modeltanks.fsnet.co.uk/tamiyam1a1.htm

They have only 3 sets of gears giving about 4x4x4 --> 64:1
wheras my geartrain has 4 sets --> 203:1. So mine may be
slower and higher torque, assuming similar motors.

- danM

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2000\12\12@013131 by Blars Blarson
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Something I found on the TLC web site: (http://www.tlc.com, search for robots
or junkyard then look at the "new series" page) If you are interested
in being on a TV program competing to build robots, send mail to
robotsEraseMEspamrbiproductions.com.  Let the list know if you'll be on it, even
if you wind up not using a PIC.
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2000\12\12@020210 by Blars Blarson

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>If you are interested
>in being on a TV program competing to build robots, send mail to
>EraseMErobotsspam@spam@rbiproductions.com.

Oops, that should be @spam@robotsspam_OUTspam.....rbiproductionsinc.com

If I get on the show, I get to travel to the exotic wilds of --
the city I live in.
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2000\12\12@023533 by Roman Black

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This is a bit of an ask, would it be possible to
have four h-bridge chips to allow two uni/bipolar
steppers driven, (or 4 dc motors) rather than just
2 for 2 dc motors? This would make it very attractive
for some of the projects I do. Also it is the perfect
size for micromouse competition which many people
prefer steppers. :o)
-Roman





Dan Michaels wrote:
{Quote hidden}

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2000\12\12@083710 by rchock, Steve

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Tom & Dan:

My little robot weighs about a pound. I am in the process of
trying to trim some of the weight off. The weight is too much
for the motors at 3VDC. They don't start to move the unit until I reach
about
3.5VDC. To be honest, I'm not sure what the torgue would be, (not
sure how I could go about figuring it). Looking at the instructions
on building the platform you are given two choices when building
the motor Normal Speed(203.7:1) or High Speed(58.2:1). As for the
the current rating, the P-CHANNEL MOSFETs I am using the 2SJ412
( http://pdf.toshiba.com/taec/components/Datasheet/2SJ412.pdf ) that
are available from Digikey at US $1.54 EA. The N-CHANNEL MOSFETs are
YTA640 from Digikey at US $1.54. I wanted an H-BRIDGE that could handle
at least 1A. Using these MOSFETs, the H-BRIDGE doesn't even get warm when
running. This is my first try at a robot, so ALOT of the stuff being
talked about here is a little over my head at this time, but I catch on
fast.

Best regards,

Steve


Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

"Great spirits have always encountered violent
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2000\12\12@113542 by Roman Black

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BEBBINGTON, LEE wrote:
>
> Hi Roman,
>
> I'm interested in robots but have not built much as yet. With three children
> I do not get much time, but I'm very interested in small robots and would
> like to see a picture of your desktop robot, so if you would not mind
> sending me a picture I would appreciate it.
>
> Thank you in anticipation,
>         Lee

Hi Lee, for yourself and maybe Dan and anyone who was looking
at small tank-style bot designs, I put up a simple page with
pictures of my little bot that uses stepper motors. The steppers
came from faxes with the integral gearboxes attached, perfect
speed and good torque for small bot. I think James asked me
once about the fax steppers too.
See it at:
http://www.ezy.net.au/~fastvid/deskbot.htm

-Roman

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2000\12\12@122951 by Dan Michaels

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Roman Black wrote:
>This is a bit of an ask, would it be possible to
>have four h-bridge chips to allow two uni/bipolar
>steppers driven, (or 4 dc motors) rather than just
>2 for 2 dc motors? This would make it very attractive
>for some of the projects I do. Also it is the perfect
>size for micromouse competition which many people
>prefer steppers. :o)


Um, not with maintaining the present SBC footprint. Also,
adding 4 chips would pretty much eat "all" the PIC I/O pins.
Each chip requires 4 control and 2 enable lines - and I am
keeping them as separated as possible to allow flexibility.

However, you "can" use the 4 separate drivers of the H-bridge
chips individually, so you can drive 8 separate windings as
it is. Wouldn't this run 2 stepper motors ok?

I guess because 2 drivers are hi-side and 2 lo-side, you could
not handle a stepper with any common lines common to all 4
windings. Have to mix and match:

Hi-side-drvr-----+           Vss
                |            |
          W1  @@@@@        @@@@@  W2
                |            |
               gnd       lo-side drvr

Wouldn't this work?
- danM

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2000\12\12@123003 by Dan Michaels

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Steve Kosmerchock wrote:
>Tom & Dan:
>
>My little robot weighs about a pound. I am in the process of
>trying to trim some of the weight off. The weight is too much
>for the motors at 3VDC. They don't start to move the unit until I reach
>about
>3.5VDC. To be honest, I'm not sure what the torgue would be, (not
>sure how I could go about figuring it). Looking at the instructions
>on building the platform you are given two choices when building
>the motor Normal Speed(203.7:1) or High Speed(58.2:1).


Yeah, that wooden dozer + tracks is probably quite heavy. Makes
me glad I decided to go with AOL CDs for the body - quite light.

BTW, did you set up the geartrain for 203 or 58? Makes a really
big difference with the little '130' motors.

- danM

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2000\12\12@125032 by Dan Michaels

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Roman Black wrote:
>
.......
>http://www.ezy.net.au/~fastvid/deskbot.htm
>

Darn, Roman, sure is nice to have a milling machine!!
[just kidding :)]. I see you did exactly what I don't want
to do - spend all my spare time building the mechanics. I
figure 9 holes in a couple of stacked AOL CDs, and I'm in
business. Maybe you should rename yours ClipBot - since its
mainstays are paper clips - good recycling use. I'll have
to get a hotglue gun - sounds like fun, quick, and easy remodeling
[I know AliceC even has a quick-draw hip holster for hers].

Sounds like yours has a lot more torque than the Tamiya
geartrain I am using. BTW, what is the big round doohicky on
the front-end? How autonomous is it?

- danM

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2000\12\12@133151 by rchock, Steve

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Dan:

I went with the 203.7:1. Less speed more torque. The wood is actually
quite lite, almost weighs nothing. I think it is called "balsa" wood (I
might be wrong).
The heavy part is the rest of the body, it is for my 3 year old son so I am
trying
to enclose everything so he can't get to the electronics.

Best regards,

Steve


Steven Kosmerchock
Radio Frequency Systems
Phoenix,  Arizona  USA
(WORK) http://www.rfsamericas.com

http://www.geocities.com/researchtriangle/lab/6584

"Great spirits have always encountered violent
oppposition from mediocre minds."--A.Einstein

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2000\12\12@134638 by Dan Michaels

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Steve wrote:

>I went with the 203.7:1. Less speed more torque. The wood is actually
>quite lite, almost weighs nothing. I think it is called "balsa" wood (I
>might be wrong).

The old balsa wood was lighter than feathers and only about
1/10 as strong. Could squeeze it flat between your fingers.
I think termites secrete it.
===============

>The heavy part is the rest of the body, it is for my 3 year old son so I am
>trying
>to enclose everything so he can't get to the electronics.
>

Thanks, I'll have to keep weight in mind, as I am using the
same motor lashup. Begins to sound like they must just something
more powerful in the Radio Shack tanks.

- danM

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2000\12\12@161642 by steve

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> >I went with the 203.7:1. Less speed more torque. The wood is actually
> >quite lite, almost weighs nothing. I think it is called "balsa" wood (I
> >might be wrong).
>
> The old balsa wood was lighter than feathers and only about
> 1/10 as strong. Could squeeze it flat between your fingers.
> I think termites secrete it.

Termites ? !!!

There are different grades of balsa wood, some denser/stronger than
others. Probably different cuts out of the log. The model aircraft
folks use an iron-on, heat shrinking film that should be available
from the same place you get balsa wood. You can make a very light and
strong composite by ironing some of that stuff onto both sides of a
sheet of balsa. Lots of fancy colours too.

Steve.


======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: spamBeGonesteveb@spam@spamtla.co.nz      fax +64 9 820-1929
======================================================

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2000\12\12@170035 by Tony Nixon

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picon face
Roman Black wrote:
>
> Duane Brantley wrote:
> >
> > Does anyone make a bridge that will handle, say, in the order of 15 - 20
> > amps peak (stall)?  I haven't done a full load test on the gear head motors
> > that I'm going to use, but I know they can easily pull 12 Amps.
> >
> > Happy Holidays,
> >
> > Duane

> Now if you can tell me about a 2A to 10A h-bridge with
> good sat voltage I would be *very* happy!! I have been
> looking for something like this for a long time. :o)
> -Roman


I used this circuit in the virtual car project. It is set up to run
isolated from the PIC supply.

FETs are good to 60 or so amps and are used for automotive seat
positioners and such.

http://www.picnpoke.com/projects/mdrive.pdf

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Tony

mICro's
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2000\12\12@172952 by Duane Brantley

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Tony, thanks for the schematic!

-----Original Message-----
From: Tony Nixon [Tony.Nixonspam@spam@ENG.MONASH.EDU.AU]
Sent: Tuesday, December 12, 2000 4:02 PM
To: EraseMEPICLISTRemoveMEspamSTOPspamMITVMA.MIT.EDU
Subject: Re: [OT]: Robotics with PIC16F877 anyone??


Roman Black wrote:
>
> Duane Brantley wrote:
> >
> > Does anyone make a bridge that will handle, say, in the order of 15 - 20
> > amps peak (stall)?  I haven't done a full load test on the gear head
motors
{Quote hidden}

I used this circuit in the virtual car project. It is set up to run
isolated from the PIC supply.

FETs are good to 60 or so amps and are used for automotive seat
positioners and such.

http://www.picnpoke.com/projects/mdrive.pdf

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Tony

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2000\12\12@174623 by Bill Westfield

face picon face
> Now if you can tell me about a 2A to 10A h-bridge with
> good sat voltage I would be *very* happy!! I have been
> looking for something like this for a long time. :o)

The darlington transistor configurations used to get high current gains
ALWAYS leave the output transistor short of saturation - this was one of
the "lightbulbs" that went off in college when we were analyzing
transistor circuits - I was quite shocked!  (Unfortunately, I don't
remember exactly WHY this is true...)

I think this means that to get low power dissipation in your h-bridge
circuits, you'll need to use MOSFETs...  (Are P-channel mosfets really
that expensive?  Can you use a charge pump or secondary supply volatge
and get the ability to use N-channel mosfets in the "high side"
drivers?)

BillW

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2000\12\12@181853 by Bob Blick

face
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> I think this means that to get low power dissipation in your h-bridge
> circuits, you'll need to use MOSFETs...  (Are P-channel mosfets really
> that expensive?  Can you use a charge pump or secondary supply volatge
> and get the ability to use N-channel mosfets in the "high side"
> drivers?)

Hi Bill!

P-MOSFETs have twice the resistance for the same die size, and are 50%
more expensive, so they end up being more than twice as expensive. It all
boils down to extra complexity. If you are running with 5 to 12 volt
supply, it's not so bad, but when you go higher, you must worry about
popping the gate with too much voltage. It gets messy. That's why so many
companies make high side chips, the IR2110 was the last one I messed with.

Cheerful regards,

Bob

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2000\12\12@233848 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

I think it would, but 8 wire steppers are very rare. Normally
they are 5 and 6 wire, especially the "free" type you strip
from old printers etc. When you buy steppers new sometimes
you can ask for 8 wire format. :o)
-Roman




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2000\12\12@235151 by Roman Black

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Dan Michaels wrote:
>
> Roman Black wrote:
> >
> .......
> >http://www.ezy.net.au/~fastvid/deskbot.htm
> >
>
> Darn, Roman, sure is nice to have a milling machine!!
> [just kidding :)].

Actually I have got one! :o) But i still like the speed
of wire metal frames, and the strength/weight factor.

> I see you did exactly what I don't want
> to do - spend all my spare time building the mechanics. I
> figure 9 holes in a couple of stacked AOL CDs, and I'm in
> business. Maybe you should rename yours ClipBot - since its
> mainstays are paper clips - good recycling use. I'll have
> to get a hotglue gun - sounds like fun, quick, and easy remodeling
> [I know AliceC even has a quick-draw hip holster for hers].

Ha ha! Actually it didn't take long to build. A couple of
hours on a rainy night. In all the days you've been talking
about CD platforms I could have built a couple of these.:o)

> Sounds like yours has a lot more torque than the Tamiya
> geartrain I am using. BTW, what is the big round doohicky on
> the front-end? How autonomous is it?
> - danM

The round thing is a ballast weight, he is meant to have
different attachments on the front. Mainly a vacuum motor.
It has plenty of torque but the main advantage is the stepper
positioning. Speed is absolute re stepper speed, so he will
trundle across the table and not even slow down when he
hits the 1kg weight, just instantly pushes it at the same
speed. I've also worked with DC motors and encoders, and
its not the same, hunting, overshoot, lag, load dependent
resonance problems, etc etc. If I can use steppers that I
have lying around I prefer that.
His main use is to act as a platform to test things,
sensors, software, etc. I can glue and solder things on in
seconds and test them easily. At the moment he's not
autonomous at all as his brain is elsewhere. :o)
-Roman

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2000\12\12@235343 by Roman Black

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Tony Nixon wrote:

> I used this circuit in the virtual car project. It is set up to run
> isolated from the PIC supply.
>
> FETs are good to 60 or so amps and are used for automotive seat
> positioners and such.
>
> http://www.picnpoke.com/projects/mdrive.pdf
> Tony


Thanks Tony, nice circuit!
-Roman

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2000\12\12@235958 by Dan Michaels

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Roman Black wrote:

>>
>> Hi-side-drvr-----+           Vss
>>                  |            |
>>            W1  @@@@@        @@@@@  W2
>>                  |            |
>>                 gnd       lo-side drvr
>>
>> Wouldn't this work?
>> - danM
>>
>
>I think it would, but 8 wire steppers are very rare. Normally
>they are 5 and 6 wire, especially the "free" type you strip
>from old printers etc. When you buy steppers new sometimes
>you can ask for 8 wire format. :o)


Hi Roman,

5-wire would definitely be a problem - one common for all
windings - but 6-wire sounds ok, if you simple think of doubling
the scheme shown above. Got any idea how popular 5- vs 6-wire
steppers are?

Further, with 2 L293's on the pcb, seems you could handle
2 5-wire steppers ok by driving 1/2 of the windings of each
stepper from one of the L293's and the other half from the
other L293. The common of one stepper would be hi and that
of the other would be low, of course, so I imagine the
control s.w. would be mirror images, or else you would have
to shuffle the order of the windings.

Would this be too much trouble?

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
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2000\12\13@002853 by Dan Michaels

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Roman Black wrote:
>>
>> Darn, Roman, sure is nice to have a milling machine!!
>> [just kidding :)].
>
>Actually I have got one! :o) But i still like the speed
>of wire metal frames, and the strength/weight factor.
>

[I know - that's why I said it].
================

>
>Ha ha! Actually it didn't take long to build. A couple of
>hours on a rainy night. In all the days you've been talking
>about CD platforms I could have built a couple of these.:o)
>

I coulda drilled 9 holes in a CD too, but I keep having to
go back and redesign my SBC every time someone mentions
something new on piclist :).
================

>
>The round thing is a ballast weight, he is meant to have
>different attachments on the front. Mainly a vacuum motor.

Where did you get a vacuum cleaner small enuf to fit on
your ClipBot, and how does it know where to go? I didn't
see much in the way of sensors on it.

And it's a he, is it? How can you tell?
==============


>It has plenty of torque but the main advantage is the stepper
>positioning.
I've also worked with DC motors and encoders, and
>its not the same, hunting, overshoot, lag, load dependent
>resonance problems, etc etc. If I can use steppers that I
>have lying around I prefer that.

Have you tried servos? They seem to be very popular with
the Handyboard set.

- danM

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2000\12\13@004057 by Roman Black

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William Chops Westfield wrote:
>
> > Now if you can tell me about a 2A to 10A h-bridge with
> > good sat voltage I would be *very* happy!! I have been
> > looking for something like this for a long time. :o)
>
> The darlington transistor configurations used to get high current gains
> ALWAYS leave the output transistor short of saturation - this was one of
> the "lightbulbs" that went off in college when we were analyzing
> transistor circuits - I was quite shocked!  (Unfortunately, I don't
> remember exactly WHY this is true...)
>
> I think this means that to get low power dissipation in your h-bridge
> circuits, you'll need to use MOSFETs...  (Are P-channel mosfets really
> that expensive?  Can you use a charge pump or secondary supply volatge
> and get the ability to use N-channel mosfets in the "high side"
> drivers?)
>
> BillW

What's with the MOSFET craze? Manufacturers of stuff we work on are
turning away from FETs in droves, all going back to bipolar NPN
for power stuff. FETs aren't the only new technology, there have
been big gains in bipolar transistor technology now too, like
low sat voltages, very high beta, high voltage, high current,
fast switching.

About 6 years back I was seeing a lot of FET switching psu's
BUT NOW they are all using NPN transistors like the:

2SC4024 100v 10A 35w lo-sat, hi-Beta, hi-Ueb TO-220 insulated

2SC4553 100v 7.5A 30W 100MHz = lo-sat, hi-Beta, internal diode
2SC4554 as above but 15A
(both in TO-220 insulated pack with Beta over 500)

2SC4558 100v 6A 30W, lo-sat B>700 TO-220 insulated

(most of these lo-sat bipolars run about 0.2vce at about half
rated current, ie the 2SC4554 I used last was about 0.2v c-e
at 7A) And remember these are NOT darlingtons. These are just
some of the TO-220 packs, if you can go to a larger package
you can get some very impressive bipolars.

For 110v/240v mains switchers they are all using bipolars like:

2SC4130 500v 7A 30w hi-speed TO-220 insulated
(a few years back they were all using FETS)

Now NONE of the major manufacturers are using FETs in their
high power or high voltage power stages, they have universally
changed to the new bipolars. Like us lowly repairers they found
that FETs are unreliable, subject to spontaneous destruction,
(especially when hot), much more subject to destruction
from transients. And more likely to destruct in a way that
damages many other components.

Many of the TV/VCR manufacturers have released modsheets
for their products showing how to replace the FET with a
bipolar, for sets that were having reliability problems.
I have never seen a modsheet that replaces a FET with a FET!
That says something...

So when you can get a 15A bipolar with a Beta over 700,
that will drive a 7A load at about 0.2vce saturation,
with 10mA base current supplied directly from a PIC pin,
with internal hi-speed flyback diode, that is more heat
and transient proof than any similar FET, comes in a
compact TO-220 package that is fully insulated so you can
just screw it to the metalwork, what do you want a
FET for?? FETs are obsolete technology guys... :o)
-Roman

PS. Now you can see why I get annoyed at 2A h-bridge chips
with 4v sat at 1A.

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2000\12\13@005046 by Roman Black

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Dan Michaels wrote:
{Quote hidden}

Hi Dan, 6 wire are most common, you get them in everything.
Maybe I misundertand your circuit? I don't think there
is any way you can drive two steppers at the same time
with two h-bridges?? Normally it takes 2 h-bridges to
drive the 2 windings in 1 motor.
-Roman

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2000\12\13@013501 by Dan Michaels

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Roman wrote:
>
>Hi Dan, 6 wire are most common, you get them in everything.
>Maybe I misundertand your circuit? I don't think there
>is any way you can drive two steppers at the same time
>with two h-bridges?? Normally it takes 2 h-bridges to
>drive the 2 windings in 1 motor.


Aww, nuts, time to reboot. Now I mucked everything up here.
Forget the last couple of messages.

Looking again, there are 4 "separate" drivers in each L293
chip that you can wire up in different ways. Each driver
output has both PNP pullup and NPN pulldown. So it only
takes 2 drivers to form one H-bridge. And obviously you
can control a 5-wire stepper with a single chip in a
straightforward manner. No funny games. Sorry.

- danM

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2000\12\13@014347 by Tom Handley

picon face
At 10:18 PM 12/11/00 -0500, Dan Michaels wrote:
>Still interested in that Radio Shack tank? I wonder if it has the
>Tamiya twin-motor in it. [you could buy one and tell me].

  Dan, I'm going to get the twin gearbox.

>>   I'm using multiprocessing with a 16F876 for testing, 12C508 for the IR
>>detector, 12C671 as a dual RC servo controller (I needed the TMR0
>>interrupt), and a 16F84 as a dual H-Bridge controller. I plan on another
>>12C508 for the Ultrasonic detector. They all talk over a serial interface.
>
>You connecting all the chips to the same RS-232 channel? How are you
>doing this? Ever think of using just a single PIC40 for the whole
>thing? But, I guess, servo control would be a problem if you have to
>keep feeding signals to it.

  As far as the RS-232, for devices that receive data, I used a simple
address scheme. Since none of the motor control modules need 8-Bit
resolution, I had plenty of room. For example, the drive motor PWM only
required 8 speeds since there is a small range of values that had any
effect. You have to experiment with this for a given motor/gearbox. In the
final version I'll be using an SPI-style interface. The two motor control
channels can share the same PIC host output using the High Bit as an address
select. The SPI inputs will require chip selects and an interrupt in some
cases.

>>The whole idea is to keep it modular with a standard interface so I can
>>easily add or remove modules (kind of like Leggo's system).

  Originally, I was going to do it all on one chip but Timer resources
became a problem with the PWM channels and the Tach. Since I tested various
parts of the design with PIC 12C5/6x and 16Fx chips, I had built up
functional blocks.

{Quote hidden}

  I could use polling but I wanted to know immediately if there was a
bumper switch hit. I had intended on 4 switches. The 74x30 was a simple hack
to expand the RB0/INT capability. I want an event-driven system so the
processor (16F877) can spend it's time on the AI responding to sensory
inputs as needed. I'm also adding external SRAM. I have a couple of CPLD
designs that provide a 19-Bit address bus and 3-4 external chip selects. One
version is for a parallel bus (Port D, CS, RD, WD) and the other uses an
SPI-style interface. We talked about this a few months ago. I have the files
on my web site, all you need to do is build a simple cable with one 74x367
and a few passives, and download the free software from Lattice. You don't
need the full package just the ispDownload software. Anyway, I'm going to
use that and a Dallas NVRAM/RTCC chip which has battery backup built-in as
well as the NVRAM in a JEDEC 28-32 pin package. I've used them in several
designs and, though spendy, they are real convenient. I may modify the CPLD
to add an interrupt priority encoder but I have to sacrifice pins somewhere.
In anycase, nothing is cast in stone yet...

  - Tom

>best regards,
>- Dan Michaels
>Oricom Technologies
>http://www.oricomtech.com


------------------------------------------------------------------------
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New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\13@014410 by Tom Handley

picon face
  Dan, thanks for the info! Ok, I'm sold. There appears to be at least one
other version of that twin gearbox. What's the P/N of the one you bought?
I checked TAMIYAs American site and got the numbers of several local dealers
but I haven't had time to call them yet. I hope to find it locally so I can
shop for shaft extensions, wheels, and a castor wheel. I want front drive
with the castor in the rear.

  As far as my R/C hack, after tearing apart old tape recorders I've had
since the 70's (I'm a real pack rat ;-), I found a decent motor and the car
can now scale the thick rugs downstairs. Again, I'm anxious to get started
on the final platform so I've got the R/C hack on hold.

  - Tom

At 01:27 PM 12/9/00 -0500, Dan Michaels wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\13@120041 by Roman Black

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Dan Michaels wrote:

> Aww, nuts, time to reboot. Now I mucked everything up here.
> Forget the last couple of messages.
>
> Looking again, there are 4 "separate" drivers in each L293
> chip that you can wire up in different ways. Each driver
> output has both PNP pullup and NPN pulldown. So it only
> takes 2 drivers to form one H-bridge. And obviously you
> can control a 5-wire stepper with a single chip in a
> straightforward manner. No funny games. Sorry.
>
> - danM


Dan, you're a legend. I was too stupid to realise
that the L293 has DUAL h-bridges. I read through my
datasheet. :o)

So your new board will drive two steppers fine!
Will the L293 be DIL style packs or the flat pack
(easier to heatsink)? I am looking forward to buying
a couple of single board units, this dual h-bridge
option will be a dream come true for many of the
applications I build.
-Roman

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2000\12\13@152549 by Dan Michaels

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face
Tom Handley wrote:
>   Dan, thanks for the info! Ok, I'm sold. There appears to be at least one
>other version of that twin gearbox. What's the P/N of the one you bought?
>I checked TAMIYAs American site and got the numbers of several local dealers
>but I haven't had time to call them yet. I hope to find it locally so I can
>shop for shaft extensions, wheels, and a castor wheel. I want front drive
>with the castor in the rear.
>

Hi Tom,

I found only one Tamiya twin-motor, but if there is another stronger
one, would be good to know about. The one I bought is seen here:

http://www.sinerobotics.com/twinmotor.html --> P/N 70097
http://www.hvwtech.com/gearsets.htm --> bottom of page

Just remember, Steve is apparently using the same one I got, and said
it does have minimal power for his 1# dozer. Still I think it will do
ok for my minibot.

The shafts stick out 1.125" [28mm] on each side of the box, total
4.25" [107mm] end to end. They are hexagonal and accept a std model
airplane wheel with .125" [3mm] diam hole with a bit of slop.
================


>   As far as my R/C hack, after tearing apart old tape recorders I've had
>since the 70's (I'm a real pack rat ;-), I found a decent motor and the car
>can now scale the thick rugs downstairs. Again, I'm anxious to get started
>on the final platform so I've got the R/C hack on hold.
>

I went to Walgreens to check out their 3 tiny R/C cars for $12,
unfortunately all the cars are 27 Mhz. Still want to hack them to
have RF comms both ways, bot<->base, but chaos with only 1 freq.
I'll go to ToysRus today and see what cheapo R/C goodies are there.

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\13@152554 by Dan Michaels

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face
Tom Handley wrote:
>
>>>   I'm using multiprocessing with a 16F876 for testing, 12C508 for the IR
>>>detector, 12C671 as a dual RC servo controller (I needed the TMR0
>>>interrupt), and a 16F84 as a dual H-Bridge controller. I plan on another
>>>12C508 for the Ultrasonic detector. They all talk over a serial interface.
>>

Do you have specs or good xmtr ckts for any ultrasonic transducers?
I got some from Jameco, but specs are minimal.
==========

>   I could use polling but I wanted to know immediately if there was a
>bumper switch hit. I had intended on 4 switches. The 74x30 was a simple hack
>to expand the RB0/INT capability. I want an event-driven system so the
>processor (16F877) can spend it's time on the AI responding to sensory
>inputs as needed. I'm also adding external SRAM.


Did you think about using the RB4-7 interrupt on change for the
bumpers? I am wavering between 4 bumper switches to RB4-7 IRQ or
feeding same to 4-way R-ladder for sampling by 1 A/D channel. It
would be polled, but I think my bot will have minimal real-time
tasks due to using the L293 chips plus hw PWM for motor control,
and not driving servos/steppers in real-time. OTOH, I did plan to
have servo capability available, so ?????????  [lotsa possibles]

My plan is to do the multi-level hierarchy mentioned a few
weeks ago. The lowest board will have a PIC40 doing all the stuff
I mentioned 2 days ago, and I'll stack above it one of my SBC40-SRM
boards [with 32KB SRAM + PIC40] for higher level stuff. Lower bd
will probably do ok with 4 Mhz xtal, higher will go 20 Mhz.
Maybe add a gameboy camera and scenix board eventually [ha].

The lower board will have some basic algorithms built-in, like
move around, don't get trapped in a corner, and find your way
around any object you encounter. Basically brainless tasks. Bump,
back up, and go the other direction. Also, find you way back home
for feeding - ie, acquire light blinking at XX hz. So using the
lower board only, the bot will be able to survive and stay fed.

The upper board will eventually have algorithms for more sophisticated
stuff. Area map building [in SRAM], remembering [SRAM memory backup
in serial EEPROM - probably have to stop the bot every minute or
so to update], sensor integration, behavior strategies, etc. The
multilevel scheme is the way living organisms work of course.
===============

I have a couple of CPLD
>designs that provide a 19-Bit address bus and 3-4 external chip selects. One
>version is for a parallel bus (Port D, CS, RD, WD) and the other uses an
>SPI-style interface. We talked about this a few months ago.

Yes, no doubt much more powerful than my SBC40-SRM PIC+SRAM pcb, but
then I built it so I guess I am obligated to use it :).
==================

>In anycase, nothing is cast in stone yet...

Story of my very life -[luckily].

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\13@153341 by Dan Michaels

flavicon
face
Roman Black wrote:
>Dan Michaels wrote:
>
>> Aww, nuts, time to reboot. Now I mucked everything up here.
>> Forget the last couple of messages.
>>
>> Looking again, there are 4 "separate" drivers in each L293
>> chip that you can wire up in different ways. Each driver
>> output has both PNP pullup and NPN pulldown. So it only
>> takes 2 drivers to form one H-bridge. And obviously you
>> can control a 5-wire stepper with a single chip in a
>> straightforward manner. No funny games. Sorry.
>>
>> - danM
>
>
>Dan, you're a legend.

Yeah - tell me about it.
=============

I was too stupid to realise
>that the L293 has DUAL h-bridges. I read through my
>datasheet. :o)
>

Bingo.
============

>So your new board will drive two steppers fine!

yes.
=========

>Will the L293 be DIL style packs or the flat pack
>(easier to heatsink)?


Present plan is 16-pin DIPs to keep the pcb low profile.
I realize this will compromise max motor size, but 1) will
have as much copper as possible devoted to heatsinking,
2) can glue small DIP-package heatsinks to chips, 3) should
handle currents ok for small bots, 4) due to 2 H-bridges in
each chip, outputs can be paralleled, and still run 2 motors,
5) big guns can use a separate H-bridge board. So........
=========

I am looking forward to buying
>a couple of single board units, this dual h-bridge
>option will be a dream come true for many of the
>applications I build.

Wow, a dream come true :). Ok, you can send the $$$ "anytime"
via PayPal. We're all in the same loop now.

best regards,
- Dan Michaels
Oricom Technologies
http://www.oricomtech.com
=========================

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2000\12\13@163016 by Alice Campbell

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Date sent:              Wed, 13 Dec 2000 15:25:54 -0500
Send reply to:          pic microcontroller discussion list <RemoveMEPICLISTRemoveMEspamEraseMEMITVMA.MIT.EDU>
From:                   Dan Michaels <KILLspamoricomspamspamBeGoneUSWEST.NET>
Subject:                Re: [OT]: Robotics with PIC16F877 anyone??
To:                     PICLISTspamspamMITVMA.MIT.EDU

{Quote hidden}

same as piezo.  either hang between 2  pins driving
oppositely, or use a transistor switch to run from highside
rail. or drive off of one pin, lowest sound. use microphone
to detect, rectify with led and use to drive a optologic
reciever to decode pulses.  :)

some code:

http://www.wizard.org/sonarcode.html


> >   I could use polling but I wanted to know immediately if there was a
> >bumper switch hit. I had intended on 4 switches. The 74x30 was a simple hack
> >to expand the RB0/INT capability. I want an event-driven system so the
> >processor (16F877) can spend it's time on the AI responding to sensory
> >inputs as needed. I'm also adding external SRAM.

alice

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2000\12\13@165225 by Peter L. Peres

picon face
>The darlington transistor configurations used to get high current gains
>ALWAYS leave the output transistor short of saturation - this was one of
>the "lightbulbs" that went off in college when we were analyzing
>transistor circuits - I was quite shocked!  (Unfortunately, I don't
>remember exactly WHY this is true...)

Thyristors are worse. A conducting thyristor has 1.2V (-0.005/deg K)
across it. The Darlington has always at least 0.6V across it because this
voltage is required to open the BE junction of the 2nd transistor
(assuming that the first saturates). I have discovered that the power
dissipation on a triac is so high and requires such a large heatsink that
I might use two diode-less MOSFETs back to back instead in a project !

P-type MOSFETs are available and not that expensive. They are often used
in audio amplifiers and in dc power grid switching (automotive among other
things). You can obtain them in TO3 which allows dissipations up into the
150W-ish (forced cooling).

Peter

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2000\12\13@165235 by Peter L. Peres

picon face
>how to measure torque

You can build a small Prony brake. Here is a crude quick and dirty way:

1. Hold motor firmly (press jaws, desk clamp etc) with axis horizontal.

2. Place shiny smooth pulley on motor axle (rubber belt pulley or wheel
pulley without tyre).

3. Take a length of thread (packing thread etc) make one turn on the motor
pulley (not overlapping). Attach the upper end of the thread to a small
weak spring (leaf spring, you can use 1/2 of a safety razor blade) fixed
above the motor. Attach the lower end of the thread to a handheld
dynamometer (or pull type letter scale, or small platen or bag to hold
scale weights).

4. Operate the motor such that it tries to pull the thread from the
dynamometer towards the leaf spring (the thread will be slipping on the
pulley). Now adjust the dynamometer force until the leaf spring is at rest
(not bending either way). The torque exerted by the motor is then: F/r
where F is the force indicated by the dynamometer and r is the radius of
the pulley. Use your favorite (non metric == aargh) measuring units. You
also need a way to count RPM at the same time. You can do this by 'eye' if
the pulley is fairly slow. Keep an eye on the ammeter while you do this.

FYI the 'best' operating area for PM and series wound dc motors is between
50 and 75% of free-run RPM for any given voltage. 'Universal' motors
designed for temporary operation and high speed motors often run at 80-90%
of free-run RPM for 'best operation'.

This kind of dynamometer is very simple, very easy to improvise and VERY
DANGEROUS. Use only with small, slow motors, and at your own risk. Big
versions of this type of dynamometer were common for motor testing until
when electrical and electronic and hydraulic dynos took over X years ago.

good luck,

Peter

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2000\12\15@101326 by Tom Handley

picon face
At 03:25 PM 12/13/00 -0500, Dan Michaels you wrote:
>Tom Handley wrote:
>>
>Do you have specs or good xmtr ckts for any ultrasonic transducers?
>I got some from Jameco, but specs are minimal.

  Dan, I haven't really spent much time on ultrasonic sensors yet. I
know several ways to build them and even have an old Heathkit intrusion
alarm around here as well as two Murata transducers. I've seen several
projects on the net. I have a lot of experience with RADAR an SONAR from
`way back when' so I may just roll my own. I remember at least one PIC-based
design somewhere. There is a lot of info on hacking Polaroids that you can
get from E-Bay for under $10.

{Quote hidden}

  I first looked at the Interrupt on Change option bearing in mind the
limitations of using that interrupt. I've used that feature in a variety of
projects. You still have to read Port B to figure out who caused the
interrupt. By using a cheap 74x30 with pull-ups on the inputs and the output
connected to RB0/INT, you get 7 interrupts. Any device pulling an x30 Input
Low, will bring RBO/INT High for the duration. Obviously, you have to plan
ahead before using this scheme. First, it takes so many cycles to get the
interrupt and read Port B, etc, so any device must keep their interrupt Low
for at least that amount of time. Then there is the problem of switch-bounce
so you could get mutliple interrupts for several ms.

>best regards,
>- Dan Michaels
>Oricom Technologies
>http://www.oricomtech.com


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\15@103410 by Tom Handley

picon face
  Dan, thanks. That's the same P/N I've seen all over the net. I saw
Steve's comments and the twin motor/gear box is too small for my needs so
once again, I'm back on first base... Option #2 is the TAMIYA High Power
or worm gear boxes. It's frustrating that TAMIYA has no specs on their web
site but if you check around the net, you can start to piece some of it
together. Tower Hobbies seem to have the best price but I have not checked
local dealers yet. I also checked Mabuchi's site for more powerful versions
of the motor used in the twin unit but I could'nt find anything that would
fit in that tight space.

  Well, *Like and Idiot!*, I tore apart my last tape deck, a Radio Shack
Optimus dual dubbing deck I bought in the early 80's. (I can hear Roman
laughing ;-) It has two Mabuchi motors that were a little more powerful
(9-15V) than the twin unit. I hacked up some old STD Bus PCB's that failed QC
back when I was designing 6809-based cards in the 80's (Told you I'm a pack
rat ;-) and used them to support the motor and gears. I had enough for two
sets and they would be identical. Well, after fumbling through all the junk
gears the best I could do was a 10:1 ratio which ended up at 320 RPM with
great torque. At 9V, good torque but still too fast. The assembly did turn
out fairly nice though. The bottom line, I'm buying a gear box...

  - Tom

At 03:25 PM 12/13/00 -0500, Dan Michaels wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2000\12\15@104814 by M. Adam Davis

flavicon
face
Well that's perfect - it'll give you 1ft/second of movement - If you use
.72 inch diameter wheels... ;-)

-Adam

Tom Handley wrote:
> Well, after fumbling through all the junk
> gears the best I could do was a 10:1 ratio which ended up at 320 RPM with
> great torque. At 9V, good torque but still too fast. The assembly did turn
> out fairly nice though. The bottom line, I'm buying a gear box...
>
>    - Tom

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2000\12\15@122116 by Dan Michaels

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The one good thing about the Tamiya is 48RPM with 203:1
gearing, so a std 1.75" diam model airplane wheel gives
you ~ 4"/sec.


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2000\12\15@122131 by Dan Michaels

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Tom wrote:
Option #2 is the TAMIYA High Power
>or worm gear boxes. It's frustrating that TAMIYA has no specs on their web
>site but if you check around the net, you can start to piece some of it
>together.

My very words. Buy it, measure it, then you know - ha.
=================

>gears the best I could do was a 10:1 ratio which ended up at 320 RPM with
>great torque. At 9V, good torque but still too fast. The assembly did turn
>out fairly nice though. The bottom line, I'm buying a gear box...
>

Check out those Tamiya single-motor geartrains. Lots more power
than the twin-motor, and all you need is 2 more screws.

-->>>  http://www.hvwtech.com/gearsets.htm --> bottom of page

I'd say also, look for something that will run at higher voltage
and draw lower current than the twin-motor.

- danM

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2000\12\15@225047 by Roman Black

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Dan Michaels wrote:

> Check out those Tamiya single-motor geartrains. Lots more power
> than the twin-motor, and all you need is 2 more screws.
>
> -->>>  http://www.hvwtech.com/gearsets.htm --> bottom of page
>
> I'd say also, look for something that will run at higher voltage
> and draw lower current than the twin-motor.

Dan, I looked at the page, the worm gearbox would be my choice.
Gearing 336:1 and no-load current 220mA. This is similar
to worm gearboxes and small motors I have played with,
they use very little power and would rip your arm off with
a little over 300mA. Depends how big your bot is going to be??
-Roman

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