12VDC motor problems

U

Uriah

Guest
I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter. It stopped working and I have taken
it apart and am stuck. What it does is that it works for about a
minute then starts slowing down and then stops. If I turn it off and
wait a minute it will do it again. There doesn't appear to be any
shorts on the wires wrapped on the inside. I am a little confused on
how this thing works. It has three brushes, two are opposite at 12:00
and 6:00 and one wired to the frame is at about 8:00. There are also
two blue Varistors??? wired between the ground and each brush, at the
input plug, not in the motor. They have CNR written on them and then
100820k under that. What are they used for? And why the three brushes
in that kind of configuration? And... how are you supposed to wire
these up? being that there are three brushes? And why does it stop
running. The manufacture in AU said that it was losing magnetic
power??, is that possible? They want over $300.00 for a direct
replacement. I found surplus motors that are close for $20.00. Any
help on this one? Thanks so much
Russ
 
"Uriah" <uriahsky@hotmail.com> wrote in message
news:62f3bd34-1f29-4dc7-b34a-17da8340f661@r37g2000prr.googlegroups.com...
I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter. It stopped working and I have taken
it apart and am stuck. What it does is that it works for about a
minute then starts slowing down and then stops. If I turn it off and
wait a minute it will do it again. There doesn't appear to be any
shorts on the wires wrapped on the inside. I am a little confused on
how this thing works. It has three brushes, two are opposite at 12:00
and 6:00 and one wired to the frame is at about 8:00. There are also
two blue Varistors??? wired between the ground and each brush, at the
input plug, not in the motor. They have CNR written on them and then
100820k under that. What are they used for? And why the three brushes
in that kind of configuration? And... how are you supposed to wire
these up? being that there are three brushes? And why does it stop
running. The manufacture in AU said that it was losing magnetic
power??, is that possible? They want over $300.00 for a direct
replacement. I found surplus motors that are close for $20.00. Any
help on this one? Thanks so much
Russ
Click to expand...
Hi Russ,
Off hand I don't know your problem.
Sometimes the third brush is for phase control and sometimes its for a
tachometer arrangement. I really don't know. It sounds as though your
electronics control devices are overheating.
When it slows down, is anything hot?

Tom
 
On Dec 30, 6:13 pm, "Tom Biasi" <tombi...@optonline.net> wrote:
"Uriah" <uriah...@hotmail.com> wrote in message

news:62f3bd34-1f29-4dc7-b34a-17da8340f661@r37g2000prr.googlegroups.com...



I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter.  It stopped working and I have taken
it apart and am stuck.  What it does is that it works for about a
minute then starts slowing down and then stops.  If I turn it off and
wait a minute it will do it again.  There doesn't appear to be any
shorts on the wires wrapped on the inside. I am a little confused on
how this thing works.  It has three brushes, two are opposite at 12:00
and 6:00 and one wired to the frame is at about 8:00.  There are also
two blue Varistors??? wired between the ground and each brush, at the
input plug, not in the motor.  They have CNR written on them and then
100820k under that.  What are they used for? And why the three brushes
in that kind of configuration?  And... how are you supposed to wire
these up? being that there are three brushes?  And why does it stop
running. The manufacture in AU said that it was losing magnetic
power??, is that possible?  They want over $300.00 for a direct
replacement.  I found surplus motors that are close for $20.00.  Any
help on this one?  Thanks so much
Russ

Hi Russ,
Off hand I don't know your problem.
Sometimes the third brush is for phase control and sometimes its for a
tachometer arrangement. I really don't know. It sounds as though your
electronics control devices are overheating.
When it slows down, is anything hot?

Tom
Click to expand...
No it doesn't get hot at all. I have it hooked to a bench power
supply and it I can watch the current draw and as it slows it pulls a
little more current. I cut the blue variistors off and it made no
difference. I checked the three coils wired on the inside and best I
can tell they seem ok. wonder how they would use the third brush
being that it is a DC motor? Thanks for the help,
Russ
 
On Tue, 30 Dec 2008 17:39:53 -0800, Uriah wrote:

I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter. It stopped working and I have taken it
apart and am stuck. What it does is that it works for about a minute
then starts slowing down and then stops. If I turn it off and wait a
minute it will do it again. There doesn't appear to be any shorts on
the wires wrapped on the inside. I am a little confused on how this
thing works. It has three brushes, two are opposite at 12:00 and 6:00
and one wired to the frame is at about 8:00. There are also two blue
Varistors??? wired between the ground and each brush, at the input plug,
not in the motor. They have CNR written on them and then 100820k under
that. What are they used for? And why the three brushes in that kind of
configuration? And... how are you supposed to wire these up? being that
there are three brushes? And why does it stop running. The manufacture
in AU said that it was losing magnetic power??, is that possible? They
want over $300.00 for a direct replacement. I found surplus motors that
are close for $20.00. Any help on this one? Thanks so much
Russ
Click to expand...
Does it slow down and stop forever, or does it recover after sitting?

If it stops forever, and it's not a rare-earth magnet type, and if you're
using way more current than the manufacturer calls out, then chances are
you're demagnetizing the field magnets.

If it stops forever, and it's getting _really_ hot, then chances are
you're overheating it and demagnetizing the field magnets (although I
think you'd notice the smoke and glowing things before then).

If it grinds to a stop then recovers, have you tried manually turning
it? It may be mechanically binding due to heat.

If it's not one of those, I'm stumped, too.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
 
Uriah wrote:
I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter. It stopped working and I have taken
it apart and am stuck. What it does is that it works for about a
minute then starts slowing down and then stops. If I turn it off and
wait a minute it will do it again. There doesn't appear to be any
shorts on the wires wrapped on the inside. I am a little confused on
how this thing works. It has three brushes, two are opposite at 12:00
and 6:00 and one wired to the frame is at about 8:00. There are also
two blue Varistors??? wired between the ground and each brush, at the
input plug, not in the motor. They have CNR written on them and then
100820k under that. What are they used for? And why the three brushes
in that kind of configuration? And... how are you supposed to wire
these up? being that there are three brushes? And why does it stop
running. The manufacture in AU said that it was losing magnetic
power??, is that possible? They want over $300.00 for a direct
replacement. I found surplus motors that are close for $20.00. Any
help on this one? Thanks so much
Russ
I would suggest that the 3rd brush is wired to another external terminal
Click to expand...
- It's for running the motor at a higher speed - It's probably a 2 speed
automotive windscreen (windshield) wiper motor after all.
I've not seen one with the 'varistors' as described, but they're most
likely to be small capacitors to provide brush noise suppression.
Does the motor slow down when run from an alternative source? The
problem may lie in the supply of the unit...
What's an 'animal crane' btw?

Jon
 
Uriah wrote:

On Dec 30, 6:13 pm, "Tom Biasi" <tombi...@optonline.net> wrote:
"Uriah" <uriah...@hotmail.com> wrote in message


news:62f3bd34-1f29-4dc7-b34a-17da8340f661@r37g2000prr.googlegroups.com...



I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter.  It stopped working and I have
taken it apart and am stuck.  What it does is that it works for
about a minute then starts slowing down and then stops.  If I turn
it off and wait a minute it will do it again.  There doesn't appear
to be any shorts on the wires wrapped on the inside. I am a little
confused on how this thing works.  It has three brushes, two are
opposite at 12:00 and 6:00 and one wired to the frame is at about
8:00.  There are also two blue Varistors??? wired between the
ground and each brush, at the input plug, not in the motor.  They
have CNR written on them and then 100820k under that.  What are
they used for? And why the three brushes in that kind of
configuration?  And... how are you supposed to wire these up? being
that there are three brushes?  And why does it stop running. The
manufacture in AU said that it was losing magnetic power??, is that
possible?  They want over $300.00 for a direct replacement.  I
found surplus motors that are close for $20.00.  Any help on this
one?  Thanks so much Russ

Hi Russ,
Off hand I don't know your problem.
Sometimes the third brush is for phase control and sometimes its for
a tachometer arrangement. I really don't know. It sounds as though
your electronics control devices are overheating.
When it slows down, is anything hot?

Tom

No it doesn't get hot at all. I have it hooked to a bench power
supply and it I can watch the current draw and as it slows it pulls a
little more current. I cut the blue variistors off and it made no
difference. I checked the three coils wired on the inside and best I
can tell they seem ok. wonder how they would use the third brush
being that it is a DC motor? Thanks for the help,
Russ
Click to expand...
Pulling more current as it slows could indicate seizing ! Are you
slowing it by adding load or is it slowing all by itself ? If the
latter it sounds like its seizing up somewhere. The third brush is
part of the speed control and may or may not be in use in your
application.

--
Best Regards:
Baron.
 
lt will slow down and stop forever, and not get hot at all. I have it
on a small bench PS and it was pulling maybe 1 amp. I don't think I
could get it going by turning it but I am not sure I tried that. It
runs fine with 12VDC for about a minute then slows and within another
minute stops. No load on the motor at all. I will check it again to
make sure I didn't miss anything. Thank you.
 
On Dec 31, 3:54 am, JonSutton <j...@killspam.com> wrote:
Uriah wrote:
I have a 12VDC wiper motor that is being used in one of those animal
cranes as a drive for a platter.  It stopped working and I have taken
it apart and am stuck.  What it does is that it works for about a
minute then starts slowing down and then stops.  If I turn it off and
wait a minute it will do it again.  There doesn't appear to be any
shorts on the wires wrapped on the inside. I am a little confused on
how this thing works.  It has three brushes, two are opposite at 12:00
and 6:00 and one wired to the frame is at about 8:00.  There are also
two blue Varistors??? wired between the ground and each brush, at the
input plug, not in the motor.  They have CNR written on them and then
100820k under that.  What are they used for? And why the three brushes
in that kind of configuration?  And... how are you supposed to wire
these up? being that there are three brushes?  And why does it stop
running. The manufacture in AU said that it was losing magnetic
power??, is that possible?  They want over $300.00 for a direct
replacement.  I found surplus motors that are close for $20.00.  Any
help on this one?  Thanks so much
Russ

I would suggest that the 3rd brush is wired to another external terminal
- It's for running the motor at a higher speed - It's probably a 2 speed
automotive windscreen (windshield) wiper motor after all.
I've not seen one with the 'varistors' as described, but they're most
likely to be small capacitors to provide brush noise suppression.
Does the motor slow down when run from an alternative source? The
problem may lie in the supply of the unit...
What's an 'animal crane' btw?

Jon
Click to expand...
That makes sense. The third brush has to do with speed. It is a wiper
motor. Those blue things could be caps. They show cap values and
test open. Maybe I don't have a strong enough PS, so I will try from
another larger PS. The crane is actually called Chocolate Factory by
ICE. Very similar to regular animal cranes but you pick up candy
bars. It drops them on a platter and then the platter pushes them
forward and if your lucky some will fall in to your arms. That
platter is the problem. You know you might be right about the PS not
being strong enough. When I found the crane broken it lost the 12
volts and the platter wasn't turning. A bridge rectifier went out so
I replaced that and I thought the motor caused the problem because of
the results I got with it on the bench. So I had ordered a surplus
motor that almost fits and the machine is back up working. I was just
puzzled about this motor and why it stops. I will test again on a
bigger PS today. I bet that that is the problem not enough
amps.....
Thank you
Russ
 
"Uriah"

I will test again on a
bigger PS today. I bet that that is the problem not enough
amps.....
Click to expand...

** So you did not even bother to monitor the DC voltage on the motor while
testing ??

How about you use a car battery for you next damn test - eh ?


...... Phil
 
On Dec 31 2008, 6:18 pm, "Phil Allison" <philalli...@tpg.com.au>
wrote:
"Uriah"

I will test again on a
bigger PS today.  I bet that that is the problem not enough
amps.....

**  So you did not even bother to monitor the DC voltage on the motor while
testing ??

How about you use a car battery for you next damn test  - eh ?

.....  Phil
Click to expand...
It is a 12VDC wiper motor. It looks like it was the low amp output of
my cheap little bench PS. I hooked it up to something bigger and it
it seems to be fine. I guess what happened was somehow the bridge
rectifier failed on the board supplying the 12VDC to the motor on the
crane. It was after I fixed the board when I tested the motor on my
bench and I assumed that because the motor would stop after a minute
that the motor was the cause of the problem. I am glad I didn't spend
the $350.00 for a replacement motor. I only lost out on about $22.00
for the surplus one. I wonder why the bridge failed? Thank you
everyone. It is a learning experience and that is why I wanted to
figure it out.
Russ
 
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