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'Signal filtering through code'
1999\08\25@140729 by Dwornik, Sebastian

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My current robotics project requires me to design and build an accurate
and stable IR proximity detection sensor system. It should give feedback
of objects up to 5 feet. My chosen tools are the PIC16F84, the
LTC1298 12-bit ADC, and the VTR24F1 optosensor from EG&G.
The sensor simply contains an IR LED and a photodarlington in a single
package.

My current solution involves simple noise filtering through code. The
opto proximity method is through the use of intensity or signal
strength,
reflected off an object.

Algorithm:
       Pulse HIGH!     ; LED ON.
       Read ADC        ; Result A = Signal + Noise

       Pulse LOW!      ; LED OFF.
       Read ADC        ; Result B = Noise

       SUB A-B ; Result C = (Signal+Noise) - (Noise)

       C = pure signal strength.

This has proven to work well for distances up to 8 inches using an 8-bit
ADC. This is the first time I'm trying to extend the range, with a more
sensitive sensor and a 12-bit ADC.

Is there a better algorithm of filtering which would provide greater
results? A better sensor, or maybe a better method to the entire
project. I have played with Sharps' GP2D02 module as well; and have
gotten rather unsatisfactory results. If the current method cannot be
improved upon, then my next step is to try one of those 40 khz
Sharp IR modules. They won't give me proximity ranging, but
maybe reliable object detection; and atleast that's a start.


Sebastian

1999\08\25@141805 by Erik Reikes

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At 02:08 PM 8/25/99 -0400, Dwornik, Sebastian wrote:
>My current robotics project requires me to design and build an accurate
>and stable IR proximity detection sensor system. It should give feedback
>of objects up to 5 feet. My chosen tools are the PIC16F84, the
>LTC1298 12-bit ADC, and the VTR24F1 optosensor from EG&G.
>The sensor simply contains an IR LED and a photodarlington in a single
>package.
>

Does it have to be IR?  I think the biggest problem going out ot 5 feet
would be to get decent returns from the reflections.  I think the easiest
way to improve your SNR would be with a bigger LED, lenses and reflectors
to focus the IR energy, or an IR laser.

Other than this I would try an acoustic approach.  Then you could use temp
compensated timing to give really accurate results.

Good luck!

-E

1999\08\25@154332 by Dan Creagan

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An Everlight or Sharp 40Khz detector, when on frequency and
properly modulated, will give you 30 to 40 inches of
detection - depending on the object reflectivity. I've
gotten hits at over five feet before, but that certainly
wasn't very reliable and such a range is pretty useless on
my robots.  I usually tune the osc off frequency to get the
range down to less than a foot.  Since I wasn't trying for
long range, I would imagine that you could do a few things
to get it - like driving multiple LEDs, making sure they are
pumping at max current, focusing the beam, etc.

Be sure you shield the LEDs with foil. Ground the case of
the detector if you are using the Sharp module (already
grounded with the Everlight).

I've used the GP2D02 and there was just a discussion on it
on the SRS list. You need to ground the case of it for a
start.  The case is plastic, but it is conductive.  One
problem with it is its narrow beam - good for ranging, but
not for general object detection.  The other is that it
really requires a separate PIC or something to handle the
code overhead for triggering and shifting in the range
(IMHO).  Acroname was publishing PIC code for driving it -
look on their website and under the GP2D02 advertisement.

Range detection by signal strength with IR is not very
reliable unless the target is stable,  has known
reflectivity and has consistent shape.  Which is not the
case for any target I'm looking for.

The GP2D02 detectors have very good noise filtering, the
Everlight and Sharp 40 Khz detectors are OK. I have not seen
a homebrew filter that would compete - though I'm sure it
could be done with PLL control of some sort.

If you want to see a PIC driver for an IR detector using an
Everlight module, then I've made one using a 12C508/9 and it
is on my site at: http://204.233.101.40/robots/brb.html . It
was also in last month's Encoder at http://www.seattlerobotics.org
.


Finally, before venturing into long range IR, why not try
Sonar? I get very consistent results with the Polaroid sonar
pack and it works out to 35 feet and in to about 6-11
inches.  You can see one at http://www.acroname.com .

Good luck,

Dan
{Original Message removed}

1999\08\25@161457 by Gordon Varney

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If you want something different, I don't know your cost restrictions, but
for $25.00 each and $18.00 in small qty. Siemens offers a 2.4 GHz Doppler
radar sensor, with antenna built in. (Part number KMY 24) A complete sensor
that will determine distance and direction by monitoring 2 sensor outputs
with your A/D microcontroller. Up to 15 feet possible,and very small in
size. (1.125"x1.5"x.375" approx.) I use them there are great. The Marshal
distributor in Kansas City MO. has stock.

Gordon Varney


{Original Message removed}

1999\08\25@164403 by Adam Davis

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The PDFs I've pulled up on this sensor indicate it will not tell you absolute
distance.  Is there a way you are getting around this?

-Adam

Gordon Varney wrote:
{Quote hidden}

> {Original Message removed}

1999\08\25@164412 by Larry Woods

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I have two points of confusion:

1. You show prices of $25 and $18, but only one part number (KMY 24)?  What
is the difference?

2. Since the KMY 24 is a Doppler device, it will not recognize an object
that is NOT
  in motion, correct?  Is this why you are using two devices?

Thanks for the clarification....

Larry Woods

> {Original Message removed}

1999\08\25@170043 by Dwornik, Sebastian

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Sounds almost perfect to what I need, except for one thing. They state,
"As the microwave radiation penetrates many materials, such as plastics
and ceramics which are opaque to light, the sensor modules can for many
applications be located hidden from view. ".  This is great for human
presence detection in automatic door opener applications, but I have no
way of telling what kind materials will come in front of the sensor
system. Have you tested it with many objects and surfaces? What kind of
results do you get? What are you using it for?

Thanks.

Sebastian

>{Original Message removed}

1999\08\25@175729 by Andy Kunz

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>Sounds almost perfect to what I need, except for one thing. They state,
>"As the microwave radiation penetrates many materials, such as plastics
>and ceramics which are opaque to light, the sensor modules can for many

Have you considered optical (laser) ranging?

Two laser transmitters set to converge at a spot at the far end of your
expected range.

Use a CCD to accurately measure the distance between the dots.  This is
linearly proportional to the distance.

Simple geometry --> simple code.

Andy

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1999\08\25@183453 by eplus1

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How do you know that the CCD is seeing a laser dot and not some other bright
dot of light?
Isn't a CCD kinda expensive?
Can you modulate the Lasers and use a photo diode with a filter with Q at
modulation frequency directed by a mirror on a pager motor? the filter
output pluses only when it sees the correct frequency and the time between
the two pluses is proportional to the distance.

James Newton, webmaster http://get.to/techref
(hint: you can add your own private info to the techref)
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{Original Message removed}

1999\08\25@184320 by Andy Kunz

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>How do you know that the CCD is seeing a laser dot and not some other bright
>dot of light?

With a CCD, you can measure the dot.  If it's not the size of the laser
(within reason), you got the wrong dot.  Also, the color would be a good clue.

>Isn't a CCD kinda expensive?

They are pretty cheap any more.  Any small camera module (<$100) will do it.

>Can you modulate the Lasers and use a photo diode with a filter with Q at
>modulation frequency directed by a mirror on a pager motor? the filter
>output pluses only when it sees the correct frequency and the time between
>the two pluses is proportional to the distance.

Don't know - why not give it a try?

Andy

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1999\08\25@191457 by Peter van Hoof

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> Two laser transmitters set to converge at a spot at the far end of your
> expected range.
>
> Use a CCD to accurately measure the distance between the dots.  This is
> linearly proportional to the distance.

there is actually no need for two lasers and two dots if the camera is
mounted a fixed distance from the laser simple trigonometry and quite
accurate if the distance between laser and camera is large enough compared
to the measured distance

The position of the dot is easy to determine
laser on, store image, laser off store image, subtract images , difference >
threshold .... this is the spot

Peter

1999\08\25@192740 by Dan Larson

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On Wed, 25 Aug 1999 18:42:01 -0400, Andy Kunz wrote:

>>How do you know that the CCD is seeing a laser dot and not some other bright
>>dot of light?
>
>With a CCD, you can measure the dot.  If it's not the size of the laser
>(within reason), you got the wrong dot.  Also, the color would be a good clue.
>

Not to mention that you can turn the laser off, take a frame, and if the
dot is still there, it wasn't the laser.  Actually, you could just take
two frames. One with lasers on and the other with lasers off.  Subtract
them.  What's left are only the laser dots and some noise, which could be
easily filtered.  Motion in the video between frames might be
a bit more work to deal with, but you can still use the afformentioned
techniques to filter it even further.

Learned this from a fellow at our local robotics club.

Dan

1999\08\25@235341 by Tjaart van der Walt

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{Quote hidden}

What I would add is an AGC circuit. Do the switching faster
than the time constant of the AGC circuit, and you should
have more sensible readings.

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1999\08\26@082340 by Dwornik, Sebastian

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Can you elaborate on this "AGC" circuit? Any examples on the web would
help.

Thank you.

Sebastian


>{Original Message removed}

1999\08\26@093109 by Gordon Varney

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> The PDFs I've pulled up on this sensor indicate it will not tell you
absolute
> distance.  Is there a way you are getting around this?
>
> -Adam
>
> Gordon Varney wrote:
> >
> > If you want something different, I don't know your cost restrictions,
but
> > for $25.00 each and $18.00 in small qty. Siemens offers a 2.4 GHz
Doppler
> > radar sensor, with antenna built in. (Part number KMY 24) A complete
sensor
> > that will determine distance and direction by monitoring 2 sensor
outputs
> > with your A/D microcontroller. Up to 15 feet possible,and very small in
> > size. (1.125"x1.5"x.375" approx.) I use them there are great. The
Marshal
> > distributor in Kansas City MO. has stock.
> >

No, actually I am using it to determine that something has indeed stepped
into or has crossed its path.
The problem is the larger the object the more signal returned. Hence, if
small is it further away?
I may be wrroonnngggg... not right, but this might not be your solution.

Gordon Varney

1999\08\26@093532 by Gordon Varney

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> I have two points of confusion:
>
> 1. You show prices of $25 and $18, but only one part number (KMY 24)?
What
{Quote hidden}

one piece at @ $25 ea.
one hundred pieces @ $18 ea.
Same part, sorry for the confusion

With Doppler, a non moving object will appear as a higher level of DC, but
not in proportion, to its size or distance.
This device is for motion detection and direction.

Gordon Varney

1999\08\26@094746 by Gordon Varney

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> Sounds almost perfect to what I need, except for one thing. They state,
> "As the microwave radiation penetrates many materials, such as plastics
> and ceramics which are opaque to light, the sensor modules can for many
> applications be located hidden from view. ".  This is great for human
> presence detection in automatic door opener applications, but I have no
> way of telling what kind materials will come in front of the sensor
> system. Have you tested it with many objects and surfaces? What kind of
> results do you get? What are you using it for?
>
> Thanks.
>
> Sebastian
>
Most plastics and cloth materials have little or no effect on RF, There fore
it will only detect objects of mass like humans, animals, walls, vehicles
and other such items. Example if you have a robot and would like to have a
detector that will tell the controller to turn or avoid an object, this
would be a great item for steering and avoidance, however the more complex
the robot the more sensors needed to determine distance and depth.
I have used it for motion control and the detector will pick up on most
objects. The larger and closer the object, the stronger the return. By
approximating the speed and  direction of the device that is carrying the
sensor, it is possible to determine if an object that is near, is standing
still or moving in relation to the sensor. A moving vehicle can then
determine if it is nearing a wall or tree, or if the object is passing it
by, or determine the rate of closure.

Gordon Varney

1999\08\26@110142 by eplus1

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<BLOCKQUOTE AUTHOR="Andy Kunz">...Have you considered optical (laser)
ranging? Two laser transmitters set to converge at a spot at the far end of
your expected range.  Use a CCD to accurately measure the distance between
the dots.  This is linearly proportional to the distance. Simple
geometry --> simple code.
</BLOCKQUOTE>

<BLOCKQUOTE AUTHOR="Peter van Hoof">...no need for two lasers and two dots
if the camera is mounted a fixed distance from the laser...</BLOCKQUOTE>

<BLOCKQUOTE AUTHOR="Dan Larson"> ...you can turn the laser off, take a
frame, and if the dot is still there, it wasn't the laser.  Actually, you
could just take two frames. One with lasers on and the other with lasers
off.  Subtract them.  What's left are only the laser dots and some noise,
which could be
easily filtered.</BLOCKQUOTE>

I've been hearing this solution for a while and I'm sure it would work
nicely. It is further described at:
http://www.cyberg8t.com/pendragn/actlite.htm

The problem(s) is(are):
1. CCDs are in the under a $100 range. Ok for the dedicated hobbyist but it
makes it hard for kids, producible products, or wife/kid limited budgets
(me).
2. Reading a CCD and finding the right spot requires
  A. Speed. the standard 4Mhz PIC just ain't going to do it in real time.
Maybe an SX.
  B. Lots of RAM, especially to take two shots and compare. And the PIC
ain't got it.
3. It just seems to me (and I wish I had time to prove it) that its not
necessary. Again, modulate the Laser(s) and use a photo diode to a filter
with Q at modulation frequency directed by a mirror on a pager motor. The
filter outputs pluses only when it sees the correct frequency and the time
between the two pluses (or from the pulse to a reference provided by a
sensor that watches the mirror spin when using only one laser) is
proportional to the distance. Easily PICable, very low cost, etc...

Actually Scott Dattalo has done a brilliant page at
www.interstice.com/~sdattalo/technical/theory/dtmf.html
on how to pick out the presence a frequency by just sampling the signal at a
regular interval (ISR) and doing a DFT on it. He uses it for 0 hardware
DTMF. Scenix did it in their single chip modem. It could be used in a PIC to
eliminate the filter and just connect the photo-diode to the PIC. Another
pin for the reference pulse and maybe a PWM out for the motor speed.

Sigh... another for the "someday" bin.

James Newton, webmaster http://get.to/techref
(hint: you can add your own private info to the techref)
@spam@jamesnewtonKILLspamspamgeocities.com
1-619-652-0593 phoneÊ



{Original Message removed}

1999\08\26@114154 by Andy Kunz

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>1. CCDs are in the under a $100 range. Ok for the dedicated hobbyist but it

I thought it was for a commercial venture from the early part of the thread.

>   A. Speed. the standard 4Mhz PIC just ain't going to do it in real time.

We used a 20MHz PIC16C73 and had time to spare.  Used NTSC input to PIC.

>   B. Lots of RAM, especially to take two shots and compare. And the PIC
>ain't got it.

But you should already KNOW where the spot is (which lines) and only need
to scan them for which columns.  Using RLL encoding (how many pixels across
_didn't_ have the spot, when it appears, how many pixels does it occupy,
then how many don't again.  Three 1-byte entries per line.  Very little RAM.

Andy

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1999\08\26@125559 by Scott Dattalo

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On Thu, 26 Aug 1999, James Newton wrote:

> <BLOCKQUOTE AUTHOR="Dan Larson"> ...you can turn the laser off, take a
> frame, and if the dot is still there, it wasn't the laser.  Actually, you
> could just take two frames. One with lasers on and the other with lasers
> off.  Subtract them.  What's left are only the laser dots and some noise,
> which could be
> easily filtered.</BLOCKQUOTE>
>
> I've been hearing this solution for a while and I'm sure it would work
> nicely. It is further described at:
> http://www.cyberg8t.com/pendragn/actlite.htm

Lawrence Livermore developed a verson of this technique to track rifle
projectiles. Apparently it was used in Bosnia to determine the source of
sniper fire.

> 3. It just seems to me (and I wish I had time to prove it) that its not
> necessary. Again, modulate the Laser(s) and use a photo diode to a filter
> with Q at modulation frequency directed by a mirror on a pager motor. The
> filter outputs pluses only when it sees the correct frequency and the time
> between the two pluses (or from the pulse to a reference provided by a
> sensor that watches the mirror spin when using only one laser) is
> proportional to the distance. Easily PICable, very low cost, etc...

It's one of those theory and practice dilemmas... The only problem with
this approach is that it only takes light 3ns to travel a meter. Now it is
possible to resolve this kind of resolution with fairly simple
electronics. I could envision two square waves: one being the square wave
gating the laser on and off and the other being the reflected signal. If
you took the difference between these and ran it through an integrator
then 'theoretically' you'd have a dc signal proportional to the phase
difference. The phase difference is proportional to the time-of-flight of
the laser pulse. The 'difference' circuit could be a 2-input AND gate and
the 'integrator' could be a low-pass RC filter. Now the major problem will
be multiple reflections. Additional problems would be calibration and
drift (specifically propogation delay changes through the various
components [because of temperature changes]). But it does sound fun...

Scott
PS thanks for the plug

1999\08\26@132733 by eplus1

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<BLOCKQUOTE AUTHOR="Scott Dattalo">It's one of those theory and practice
dilemmas... The only problem with this approach is that it only takes light
3ns to travel a meter. Now it is possible to resolve this kind of resolution
with fairly simple electronics. I could envision two square waves: one being
the square wave gating the laser on and off and the other being the
reflected signal. If you took the difference between these and ran it
through an integrator then 'theoretically' you'd have a dc signal
proportional to the phase difference. The phase difference is proportional
to the time-of-flight of the laser pulse.</BLOCKQUOTE>

Err... I think you may have misunderstood me. I was suggesting the use of a
rotating mirror to direct the attention of the photo diode across the plane
of the laser. For example, if the laser and mirror are mounted horizontally
from one another, the laser reflection will be somewhere on the horizontal
line scanned by the mirror. As the mirror turns, different points along that
line become visible to the photo diode. When the mirror reflects the point
that the laser "dot" is illuminating, the signal from the photo diode begins
oscillating at the frequency of the lasers modulation. This signal is
detected by a filter (analog or digital) and produces the pulse that is
detected by the processor. If the laser is on the left and the mirror on the
right, closer objects will cause the reflected "dot" to appear further to
the left from the viewpoint of the scanning mirror (pulse appears sooner)
and more distant objects will cause it to appear farther to the right (pulse
appears later) . The purpose of the modulation is only to quickly
distinguish the laser "dot" from other light sources as the mirror scans
across it.

The first picture at
http://www.cyberg8t.com/pendragn/actlite.htm
shows the mechanical setup except that I would replace the laser with the
photodiode so that different lasers could be used.

<BLOCKQUOTE AUTHOR="Andy Kunz">... NTSC input to PIC. ... already KNOW where
the spot is (which lines) and only need  to scan them for which columns.
Using RLL encoding (how many pixels across _didn't_ have the spot, when it
appears, how many pixels does it occupy, then how many don't again.  Three
1-byte entries per line.  Very little RAM. </BLOCKQUOTE>

Andy, you are absolutely clever... the CCD NTSC to PIC pin and count the
lines then the level is brilliant. If the laser modulation was genlocked to
the NTSC frame then you could look for the dot to be there then not be there
etc... just one bit to hold the expected value. The final data after 2
frames is just the depth of the point the laser is hitting. My only
objection left is the cost of the CCD. And the advantage of the CCD is that
any of the scan lines can be searched which would allow a laser with a beam
to line lens to produce an entire (vertical) 3d profile using only as much
memory as you wanted to store the results. Shifting that side to side
(slowly) would get you an entire 3d map of the objects in front.

James Newton, webmaster http://get.to/techref
(hint: you can add your own private info to the techref)
spamBeGonejamesnewtonspamBeGonespamgeocities.com
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1999\08\26@164534 by Anne Ogborn

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Just sweep the laser -
get a rotating mirror (lots of them around surplus).
Put a photodiode in front of the laser as it starts it's sweep
across, and another behind a lense focused on the scene ahead.
When the laser reaches a given point, it will reflect off the
scene into the receiver. The time difference is a one to one function
of the range

Optical problem with this (and the CCD idea) is where to focuse
the lense.

BUT, what all these approaches fail to deal with is the
case where the "range" isn't constant across the
field of view. Imagine a robot approaching the corner of
a cubical box at
a 45 deg. angle to the sides. What the range is depends on where
you measure.

You can get an array of range measurements by combing my approach above
with the CCD approach. Scan the laser slowly, and take an
angle measuring snapshot with the CCD every degree or so. Work out
the trig and you'll get a set of points that should represent the
reflecting surface.


::Annie is seen dragging a glass topped table down the hall,
a look of gleam in her eyes::

The really serious hi tech solution

Use two CCD's - mount them a distance apart to make stereo vision.

Use the morphing algorithm to map pixels in one "eye" to pixels in the
other. The distance between pixels is a function of 1/distance, so
you have a map of distances.

Voila! Depth perception.


--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\08\26@165406 by Anne Ogborn

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OK - my sickest range finder yet.

I take the issue is to get some overall sense of the proximity of
an obstructing object, with information about it's proximity
(more than one bit).

(And, I raise the question, do you need more than one bit? If
it's collision detection, probably not).

Put a fan on the front of the robot. Off to the sides mount
small aluminum foil "flags" on a low - friction bearing (say
a length of fine thread) and photodetectors to sense the
position of the foil.

When the robot approaches an obstruction, the wind will be
reflected back and move the foil flags.

::Annie is seen dragging a roll of chicken wire down the
hall, cackling with glee::



--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\08\26@171506 by Dan Creagan

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We are now aiming for the Rube Goldberg award.  However, I
think this is weird enough to almost work. If some method of
getting the resolution down to, say, the width of a chair
leg (chair legs are not nice - office chairs with those five
different arms that trap unsuspecting 'bots are EVIL) then
it would be a hoot to make one.

Dan

{Original Message removed}

1999\08\26@172308 by Gordon Varney

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> OK - my sickest range finder yet.
>
>
> ::Annie is seen dragging a roll of chicken wire down the
> hall, cackling with glee::
>
>
>
> --
> Anniep

Stand back Anne is on a roll.

Anne,
I am impressed, your ideas might just work. Do you hold patent's on these
ideas?
Can I use them? how much do you want in royalties?

Gordon Varney

1999\08\26@172915 by Andy Kunz

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>Optical problem with this (and the CCD idea) is where to focuse
>the lense.

Sorry,  I assumed you all know that because the laser is intense, you can
cut the aperture _waaaay_ down.  This allows you to have a VERY WIDE focus
range.

Andy
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1999\08\26@202533 by Anne Ogborn

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Dan Creagan wrote:
>
> We are now aiming for the Rube Goldberg award.  However, I
> think this is weird enough to almost work. If some method of
> getting the resolution down to, say, the width of a chair
> leg (chair legs are not nice - office chairs with those five
> different arms that trap unsuspecting 'bots are EVIL) then
> it would be a hoot to make one.
>
> Dan
>

Years ago MIT had a robot maze race, and the winner was
a wall follower made, if I recall, from a fan ducted
under a piece of styrofoam board to make a tiny hovercraft.
Seems like a natural for such a beasty.

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1999\08\27@005011 by Tjaart van der Walt

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Anne Ogborn wrote:
>
> Just sweep the laser -
> get a rotating mirror (lots of them around surplus).
> Put a photodiode in front of the laser as it starts it's sweep
> across, and another behind a lense focused on the scene ahead.
> When the laser reaches a given point, it will reflect off the
> scene into the receiver. The time difference is a one to one function
> of the range

I had an idea that I've been trying one of my buddies
(Hi Jules!) to try in his security R&D business.

It goes like this :
You suspend a light circular mirror from a stiff nylon fibre
with the reflective surface pointing down (dia = 3cm)
Stuck to the back of the mirror, there are three small magnets
(pointing up). Above the magnets, there are three small coils
with enough pull to deflect the mirror 45deg. Now you can scan
360deg. with a laser diode pointing upwards. Next to the diode
you have a light dep diode. As you scan the mirror, you record
the light intensity levels in, say 90 steps. These values are
saved in RAM, and the average calculated. The average is used
to normalise the saved values. This set of normalised, saved
values is compared to a pre-saved set of values (RMS sounds OK
for an indication), and any funny values will indicate an object
that shouldn't be there.

You could also use an AGC (Automatic Gain Control) circuit to
keep the measured values useable. For an AGC circuit, I think
the easiest would be to use a MOSFET like a VN10KM (Supertex)
in series with the Ri of an opamp. You need a non-inverting
amplifier for it to work. Stick the light level ouput of the
optical device into Ri. Use an integrated version of the output
to drive the MOSFET.

I probably didn't make any sense...

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1999\08\27@005026 by Tjaart van der Walt

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"Dwornik, Sebastian" wrote:
>
> Can you elaborate on this "AGC" circuit? Any examples on the web would
> help.

I did in another post.

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1999\08\27@104058 by Dwornik, Sebastian

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I must thank you all for the excellent input to my
dillemma. It has been very helpful, and amusing.

I have experimented some more with just the VTR24F1
retro-reflective opto-sensor, and the results are
excellent for short range (4-8 inches). Which I
may then use as a downward looking sensor for path
correction. As for a reliable frontal object
detection with greater range; I will do some more
R&D and experiment with some of Sharps' modulated
IR devices. This seems to be a popular and proven
method, used by many robots. Proximity detection
and path prediction of the object being sensed
will come a bit later. I speculate that a variety
of IR sensing methods will be used to determine
as much valuable information of whats up ahead
as possible. Maybe three different sensing methods.
Long, medium, and short range tracking. Such a
combination, with added redundancy might prove
to be accurate and reliable
(hopefully fast too, 50+ Hz).

The economics of such a solution might be
high ($100+ for full setup), but worth it if
the results are good.

Thanks.


Sebastian


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