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PICList Thread
'motor direction'
1998\07\25@014626 by Aldi Navarro

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Good day !

Presently I'm doing a counter for my transformer winder machine using
this 16C84.
However, I need to determine the direction of the rotation in order to
know the
correct no. of turns by considering the addition and subtruction of
turns which depends
on the direction of the rotation of my motor.

Can anybody  give an idea on the way to detect the direction of the
motor in simplest
manner or any.

Thank you gentlemen!

aldi.

1998\07\25@061001 by Peter L. Peres

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On Fri, 24 Jul 1998, Aldi Navarro wrote:

> Good day !
>
> Presently I'm doing a counter for my transformer winder machine using
> this 16C84.
> However, I need to determine the direction of the rotation in order to
> know the
> correct no. of turns by considering the addition and subtruction of
> turns which depends
> on the direction of the rotation of my motor.
>
> Can anybody  give an idea on the way to detect the direction of the
> motor in simplest
> manner or any.

Use two reflective photo-sensors in quadrature to detect a piece of
reflective aluminium mirror glued to a rotating part in the machine. The
point must be after the friction slip clutch (I hope that your machine has
one).

hope this helps,

       Peter

1998\07\25@094425 by paulb

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Peter L. Peres wrote:

> On Fri, 24 Jul 1998, Aldi Navarro wrote:
>> Presently I'm doing a counter for my transformer winder machine using
>> this 16C84.
>> However, I need to determine the direction of the rotation in order
>> to know the correct no. of turns by considering the addition and
>> subtraction of turns which depends on the direction of the rotation
>> of my motor.

> Use two reflective photo-sensors in quadrature to detect a piece of
> reflective aluminium mirror glued to a rotating part in the machine.

 I suspect a magnet, or pair of magnets opposite, and reed switches
would suffice.
--
 Cheers,
       Paul B.

1998\07\25@115238 by Thomas McGahee

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Aldi,
The simplest way to determine the direction and # of revolutions
of your transformer winding machine would probably be a quadrature
detector. If you only need one pulse per rev, then you can get
by with a single shaft marker and two detectors or pickups.

The actual type of 'marker' and 'detector' is up to you. You
can use:

1) a reflective material and two photo-refelective detectors.

2) a magnet on the shaft and two reed switches as pickups.

3) a magnet on the shaft and two Hall effect pickups.

4) A commercial quadrature shaft decoder (see my recent post).

If making a home-made quadrature shaft decoder, keep in mind that
the fundamental signal desired is an overlapping signal like so:

                -----                     -----
A----------------|   |---------------------|   |-------------

                  -----                     -----
B------------------|   |---------------------|   |-----------

As the shaft rotates CW the A and B inputs will change as follows:

A B
0 0
1 0
1 1
0 1
0 0 etc.

As the shaft rotates CCW the A and B inputs will change as follows:

A B
0 0
0 1
1 1
1 0
0 0 etc.

The program keeps a copy of the previous state of A and B, and
compares them with the current state. When there is a change, then:

1) Register the current state in CurrentAB (as it may bobble).

2) you can determine whether the rotation was CW or CCW. You save
this info in a direction register.

3) You also update the Counter by either adding or subtracting, based
on the current Direction.

4) You replace OldAB with CurrentAB.

Note that is there is bobble, then the next time the program segment
is run the count and direction will be updated, so bobble is not
really a problem at all!

You can initialize the system by
setting the OldAB to be the same as the sensor detected AB, and the
direction as either CW or CCW (it will get updated as shaft rotates).

Hope this helps.
Fr. Tom McGahee


----------
{Quote hidden}

1998\07\25@132638 by Peter L. Peres

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On Sat, 25 Jul 1998, Paul B. Webster VK2BZC wrote:

> Peter L. Peres wrote:
>
> > On Fri, 24 Jul 1998, Aldi Navarro wrote:
> >> Presently I'm doing a counter for my transformer winder machine using
> >> this 16C84.
> >> However, I need to determine the direction of the rotation in order
> >> to know the correct no. of turns by considering the addition and
> >> subtraction of turns which depends on the direction of the rotation
> >> of my motor.
>
> > Use two reflective photo-sensors in quadrature to detect a piece of
> > reflective aluminium mirror glued to a rotating part in the machine.
>
>   I suspect a magnet, or pair of magnets opposite, and reed switches
> would suffice.

I deduce from the use of the word 'motor' in the original posting that the
speed of the unit might slightly exceed the capability of micro-switches.

Peter

1998\07\25@151055 by Bob Blick

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>> > Use two reflective photo-sensors in quadrature to detect a piece of
>> > reflective aluminium mirror glued to a rotating part in the machine.
>>
>>   I suspect a magnet, or pair of magnets opposite, and reed switches
>> would suffice.
>
>I deduce from the use of the word 'motor' in the original posting that the
>speed of the unit might slightly exceed the capability of micro-switches.

Note that you might be able to save a little processing power if you use a
d-type flip-flop hooked to the sensors, instead of determining direction
with the PIC. Hook one sensor to the flip-flop clock and also to the PIC,
and the other sensor to the data in of the flip-flop. Use the q output of
the flip-flop as the direction signal to the PIC. You still use two PIC
pins, but one will be clock, the other direction.

Cheers,
Bob

http://www.bobblick.com/

1998\07\25@174510 by Morgan Olsson

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At 12:06 1998-07-25 -0700, you wrote:
{Quote hidden}

- Warning! -
Just don«t use this for exact position feedback!

Ive seen this setup even in my schoolbook for postioning :(
For postioning it has a severe bug:
Consider the case that the movement go back and forth only so much that the
clock, but not the data change state.

You will then be feeding the PIC with clock pulses, but the same direction.
SO the PIC will believe there is acontinuous motion, although there may
only be mecanical vibration!

For only direction and speed detection it is OK to use this cirquit,
altgough I would prefer using a PIC port with interrupt on change.

Regards
/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrtspamKILLspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\07\26@095226 by paulb

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Peter L. Peres wrote:

> I deduce from the use of the word 'motor' in the original posting that
> the speed of the unit might slightly exceed the capability of micro-
> switches.

 I wouldn«t have thought the winding bobbin was directly driven by the
motor, so it shouldn«t be *that* fast.  My presumption was that the
lifetime of a *reed* switch would cover the number of turns on a
reasonable number of custom-made transformers or whatever is being
considered.

 Actually, I made further assumptions.  The reference to the need to
count back suggested that the number of turns was critical.  This
further implies the number is relatively low and not particularly fast.
The tone of the posting suggested a non-commercial application (i.e.,
you don«t cut costs on sensors on factory equipment ;-).

 For a (mass-)production system I would change my recommendation to
hall-effect switches immediately.  Either way, the idea of mounting two
magnets diametrically opposite for balance, but offsetting two sensors
on opposite sides so that they are not quite 180Ó (specifically,
adjusted so their overlap dwell equals their non-overlap dwell) seems a
neat way to do it.

 I think of coil-winding machines in the same fashion as lathes (comes
from using one for the other) in which environment optical sensors are
a no-no!

 Cheers,
       Paul B.

1998\07\26@104032 by Chuck Rice

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At 1:11 AM -0700 7/24/98, Aldi Navarro wrote:


> Good day !
>
> Presently I'm doing a counter for my transformer winder machine using
> this 16C84.
> However, I need to determine the direction of the rotation in order to
> know the
> correct no. of turns by considering the addition and subtruction of
> turns which depends
> on the direction of the rotation of my motor.
>
> Can anybody  give an idea on the way to detect the direction of the
> motor in simplest
> manner or any.

If you just want simple, connect a magnet to the shaft, and put a coil
around it. It then becomes a small generator. Add a diode, and a zero
voltage is CCW or stopped (or really slow), and + voltage is CW.
Should be good enough for a winding machine. -Chuck-

__________________________________________________________________________
Chuck Rice                                     <.....ChuckKILLspamspam.....WildRice.com>

1998\07\26@120204 by Peter L. Peres

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 First, I'll answer your posting, Paul, and then I'll show in detail how
I once built a very good and safe coil winding machine from a scrapped
dot-matrix printer stepper motor, that could be revived as a PIC project
imho.

On Sun, 26 Jul 1998, Paul B. Webster wrote:

{Quote hidden}

Hmm. Assuming 1E6 life, and 1000 turns total per unit to be done, the
switches (being two of them) would be about dying after 700 units done.
Ok, that's a lot for amateur use, but then if one has very few to do, then
one can wind by hand and count ;) Also, I suppose that the user would go
on hearing click-click click-click in his head for a long time after
stopping the unit.

>   Actually, I made further assumptions.  The reference to the need to
> count back suggested that the number of turns was critical.  This
> further implies the number is relatively low and not particularly fast.
> The tone of the posting suggested a non-commercial application (i.e.,
> you don4t cut costs on sensors on factory equipment ;-).

The one sound use for counting back on windings is when doing accurate
balanced transformers and hybrids for high-end valved audio. Nobody winds
600 ohm bal/unbal transformers by hand anymore. Also, metal detector
loops, but those are done by hand on a jig due to size ;)

- snip -
>   I think of coil-winding machines in the same fashion as lathes (comes
> from using one for the other) in which environment optical sensors are
> a no-no!

imho, 2 big mistakes here:

1. Lathes are NOT coil-winding machines, unless the shaft can be equipped
with a torque limiter. This is not a matter for joking or experimenting,
take it very seriously. This includes small table lathes, unless
hand-driven. Foot-driven ones are dangerous for coil winding. Also, no
lathe should EVER be operated with an improvised jig to hold ANYTHING in
it, unless the jig is correctly machined and tested for strength.
Human-operated lathes are among the most dangerous work machines in use.
They have all the work piece and the tool exposed to touch and in case of
accidental fragmentation the probability that the operator is hurt is in
the 30-40% range. If, additionally, the operator can be pulled by a tether
(such as, winding wire) to the moving parts, things can get even worse.
Very, very, very bad.

2. Optical sensors are used a lot in lathes, both reflective and
transmissive, but only in locations where they are capsulated and
protected from debris. Hall sensors are 'out' near the parts and work head
in most fine mechanics part processing machines because many times pieces
and materials get to be processed that cannot be exposed to magnetic
fields of any kind, or are themselves strongly magnetic, and the sensing
tolerance of hall sensors is not good enough. Instead differential HF
proximity (Q) sensors are used, and more recently, low power laser-based
sensors that can be placed pretty far from the work piece and head (in CNC
only). Precision position sensors with great travel are almost always
optical (quadrature or Gray using Moire effect, precision-geared to the
moving part), and there is no replacement in sight. Most optical sensors
use infrared, except high precision, which use visible but are totally
capsulated.

 Last, I'd like to say that I once made a coil winding machine using a
large stepper motor from an old printer. It worked out to be very good,
durable, simple to build, and could be a PIC project. The motor was driven
by a 555 timer, a CD4017 decoded decade counter used to count to 8
(obtained by connecting the 9th output to the reset pin of the 4017), and
4 Darlington transistors. 8 1N4148 diodes turned the 8-phase output from
the 4017 into 4-phase half-stepping drive (chosen for smoother torque) for
the motor. Power was 12 Vdc / 0.8 A or so, and the machine was very simple
mechanically, yet powerful enough to wind 1 mm wire on a 25 mm core. The
speed range was small but the stepper motor gave constant speed (unlike
the runaway of an uncontrolled DC motor), solid torque, including holding
torque, and is an inherent torque limiter, all this without using any kind
of gears.

 The speed control was a potentiometer in the 555 circuit. Its switch
would cut out the output of the 555 completely by opening the charge
cap. resistor circuit completely. This gave stopped motor+holding torque,
without glitches at switching.

 To reduce the torque, I simply turned the bench PSU voltage that powered
this unit down to 9 or 6 V. The circuit continued to work well, with some
speed change from the 555, and lower max. speed.

 The motor was biphase (6 wires, 2 center-tapped coils), and I used BDX53
Darlingtons and 1N4007 kickback damper diodes for each phase coil.

 Mechanically, I used a piece of 1mm mild steel sheet to hold the motor
in a small desk vise. The sheet was cut in a rectangular piece as wide as
the motor and three times longer. The sheet was screwed to the motor using
its mount holes at one end of the sheet and the protruding 'tail' of the
sheet was twisted 90 degrees to have the axle parallel with the desk edge
when the lower end was held in the vise. The motor would rest on the tail
end of the vise by bending the sheet towards the desk. The electronics
were on a bread-board and connected to the bench PSU and to the motor, the
latter using the original connector from the printer.

 Jigs to hold coils were affixed with 2 or 4 machine screws to the
cylindrical aluminium hub that was originally on the motor shaft. I just
bored and threaded the 4 holes symmetrically placed on a circle at the
front end of the hub, for 3 mm machine screws. I used to make jigs out of
rigid PVC tubing, cardboard and Balsa wood. I did not use a counter, there
was a paint dot on the hub ;) The shaft attained 4-5 rot/sec (300 rpm)
which is easy to count ;).

 This could be a PIC project too. A PIC and a ULN 2803 would be all
that's needed. And it's MUCH safer than a misused electric drill or lathe.

hope this helps, and sorry for the long posting,

       Peter

1998\07\26@123201 by Peter L. Peres

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On Sun, 26 Jul 1998, Chuck Rice wrote:

- snip -
> If you just want simple, connect a magnet to the shaft, and put a coil
> around it. It then becomes a small generator. Add a diode, and a zero
> voltage is CCW or stopped (or really slow), and + voltage is CW.
> Should be good enough for a winding machine. -Chuck-

Beware the 'real slow'. Winding machines tend to be run very slowly, and
you need a multi-pole generator for reliable operation, which is more
expensive than a commercial optical quadrature encoder. So use a
quadrature encoder. If on a tight budget, examine the possibility to use
your previous mouse's innards (2 very good quadrature encoders provided,
some assembly required ;). Belt-coupling should be ok, use a flat & wide
VCR belt and a medium VCR belt wheel on the encoder shaft, running the
belt directly on the winding machine's shaft in a safe flat place. Belt
slip should not be a problem with the torque (not) required to turn the
encoder, just don't make the belt too tight.

Peter

1998\07\26@140935 by wft

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1)   attach a small DC motor to your motor.  voltage polarity from DC
motor will change when direction changes.  (use small DC motor as
generator.
2)   Use hall effect sensor and little magnets   (north/south detection
will reverse when direction reverses.
3)    put a cog on the shaft which pushes a whisker wire attached to a
switch (or opto interupter) one way when rotating CCW and the other way
when rotating CW.

Gus
--
Gus Calabrese    Lola Montes      WFT Electronics
4337 Raleigh Street      Denver, CO 80212
303 964-9670......voicemail      EraseMEwftspam_OUTspamTakeThisOuTfrii.com   http://www.frii.com/~wft

EMERGENCY:   791 High Street     Estes Park, CO  80517
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1998\07\27@133609 by Harrison Cooper

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               Use a hall effect sensor, two magnets seperated for
forward, single magnet for reverse.  Two pulses would then indicate
forward, one for reverse.  Key is the be able to see both pulses (so
depends on speed of the motor).  If its running too fast, then you won't
see em both.  Otherwise, if this motor is be controlled from a starter,
then use an aux contact and feed it to the pic.

1998\07\27@133634 by Joe McCauley

picon face
If you want reasonably accurate results you could use an optical encoder
unit from HP.
These give out two pulse trains. One of them leads or lags the other by 90
degrees depending on the direction of rotation. This can be detected by
connecting one pulse train to the D input of a D-type flip flop, and
connecting the other to the clock input of the same flip flop. Now what you
do is to count the pulses from one of the channels of the optical encoder
to get rotation info and read the output of the flip flop to get the
direction info. You can also dispense with the flip flop and do all inside
the pic by sampling the state of one channel when the other changes state.
You may get some jitter on the count if you change direction often, but as
the encoder has 1024 pulses/rev you might be OK. I am doing this for a coil
winding machine I am building which requires high accuraccy (I'm making 2
coils which have to "see" the exactly the same ammount of magnetic flux for
high field measurements, therefore all errors in the coil construction are
important. For transformer winding this may be overkill).

Joe

At 07:39 26/07/98 -0700, you wrote:
{Quote hidden}

1998\07\27@133715 by : Cassie Carstens

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Aldi
You might want to look at the HCTL-2000, 2016 and 2020 Quadrature
Decoder/Counter Interface ICs from Hewlett Packard. It does a lot in
hardware and your pic has to read the 8 data lines and some other
pins. I can give you a sort description if you Email me direc.
Regards
Cassie

{Quote hidden}

1998\07\27@141726 by Mark Winters

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>>> Harrison Cooper <spamBeGonehcooperspamBeGonespamES.COM> 07/27/98 8:09 AM >>>
               Use a hall effect sensor, two magnets seperated for
forward, single magnet for reverse.  Two pulses would then indicate
forward, one for reverse.  Key is the be able to see both pulses (so
depends on speed of the motor).  If its running too fast, then you
won't
see em both.  Otherwise, if this motor is be controlled from a
starter,
then use an aux contact and feed it to the pic.

1998\07\27@150333 by paulb

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Peter L. Peres wrote:

> I once built a very good and safe coil winding machine from a scrapped
> dot-matrix printer stepper motor, that could be revived as a PIC
> project imho.

 Yeahh.  Love the idea.  Something useful to do with one of *all* those
steppers I have this compulsive urge to collect.

> Hmm. Assuming 1E6 life,

 I kind of thought (vacuum) reed switches had a life expectancy *much*
greater than this.

> Also, I suppose that the user would go on hearing click-click
> click-click in his head for a long time after stopping the unit.

 More like "tink-tink".  I know what my telephone exchange is doing
when I'm sitting in the office, though my secretaries don't seem to make
the same connections(!).

> 1. Lathes are NOT coil-winding machines, unless the shaft can be
> equipped with a torque limiter.

 Quite so.  This has proven a major limitation in the past, and the
stepper motor idea will amuse my father (chief coil-winder) no end!

> 2. Optical sensors are used a lot in lathes, both reflective and
> transmissive, but only in locations where they are encapsulated and
> protected from debris.

 Thus my comment to the effect; not for the amateur/ cheap job.  I have
however picked up some Logitech trackball assemblies from a local
disposals source.  The difference in the mechanics to a "cheapie" is
impressive.

 They contain three bearing points for the ball which appear to be
(synthetic) jewels (but could just be ceramic/ glass), and a
cantilever/ spring assembly to hold the "followers" against the ball.
The follower is a roller of fairly stiff foam which might wear if used
against an uneven surface, but has tremendous grip and shouldn't be put
off by dust.  I could envisage "hacking" this mechanism to follow a
slow, dry, smooth shaft quite well.  But not precision.

>  This could be a PIC project too. A PIC and a ULN 2803 would be all
> that's needed. And it's MUCH safer than a misused electric drill or
> lathe.

 Hmmm.  I'm thinking, along with the multiplexed seven-segment display,
it would automate really well.  No point using a PIC if it doesn't do
all the precision counting!  I can visualise a joystick or lever
forward/ backward control ("jog shuttle").

> hope this helps, and sorry for the long posting,

 Naah, for you, Peter, it was brief!
--
 Cheers,
       Paul B.

1998\07\27@233551 by ssj

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> Peter L. Peres wrote:
>
>

Dismount a mouse, it's cheaper and have either a dual optical sensor or an
encoded wheel, you can even use the whole mouse to count up and down...:)))))

{Quote hidden}

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