12 volt electric motor problem

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12 volt electric motor problem

This topic has 24 replies, 16 voices, and was last updated 3 September 2022 at 18:48 by bernard towers.

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1 September 2022 at 22:11 #612037
David Tocher
Participant
@davidtocher94033
I want to power the X and Z axes on my Sieg SX2.7 mill. I recovered two window winder motors from a Renault Scenic which have integral worm drives which might be up to the job.

The motors have two fat and three thin wires emerging from a black box mounted on the motor which contain, I'd guess, some electronics. After removing this box there are two fat connections going into the motor. I connected these to a power supply and the motor spins but only runs in short but consistent bursts – maybe a second or two.

I removed the brush end bearing cap to see if I could see something unusual inside but it's a plain permanent magnet motor with the brushes directly connected to the two terminals. I applied power, with the bearing end cap missing, and I can get the motor to spin normally some of the time but not always. Cleaning the brushes and commutator doesn't seem to be the answer. The brushes seem to be solid copper rather than carbon – is this usual?

Thinking the motor has duff rotor windings I tried the other with it spinning in exactly the same burst mode. I don't believe they are both faulty but . . . .

Any ideas as to what could be wrong?

Edited By David Tocher on 01/09/2022 22:12:45
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1 September 2022 at 22:11 #11301
David Tocher
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@davidtocher94033
1 September 2022 at 22:45 #612040
noel shelley
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@noelshelley55608
May be the self parking function is operating ! the brushes may be of powdered copper/carbon. Silly me, yes winder motors, was thinking of wiper motots which might be a better bet as rated for long running as opposed to intermittant. noel

Edited By noel shelley on 01/09/2022 23:08:46
1 September 2022 at 22:55 #612042
Frances IoM
Participant
@francesiom58905
the thin wires probably go to 1 or 2 hall devices that seem to determine if the motor has stalled.

Those I’ve acquired run constantly when power is applied
2 September 2022 at 00:40 #612048
duncan webster 1
Participant
@duncanwebster1
Window winders have a system which detects if a child's neck is trapped, and some have a sensor built into the motor to tell the control system when it's fully up/down
2 September 2022 at 05:45 #612053
David Tocher
Participant
@davidtocher94033
As I wrote in the OP I removed the electronics and was applying power directly to the two brush terminals.
2 September 2022 at 06:46 #612054
not done it yet
Participant
@notdoneityet
Forgive me for asking, but are there only the two fat wires going into the motor? You make it clear that there are two other wires emerging (or entering) the black box, but not that there are only two fat wires to the motor.
2 September 2022 at 06:59 #612055
David Tocher
Participant
@davidtocher94033
Only the two motor connectors go into the motor as everything else has been stripped out. There's only the two stator permanent magnets, brushes and the rotor/commutator left inside the motor.
2 September 2022 at 07:24 #612061
John Haine
Participant
@johnhaine32865
DC geared motors are so cheaply available these days off eBay that trying to use old car motors is just a waste of effort, as I think you may be finding.
2 September 2022 at 07:29 #612062
Werner Schleidt
Participant
@wernerschleidt45161
It is difficult to say what is wrong. Please apply power at the brushes or the wires to the brushes over a controllable power supply. If you have no controllable 12 V power take a 12 V battery and connect in serial a 12 Volt light from a car front lamp 12 V 45/50 W H3 or H4 . If you connect your motor the current flow over the lamp to the battery. A normal Ok motor needs about 2 to 3 A during running whithout load and the lamps starts to glow with low light.

With your faulty motor in case of a shortage the lamp glow bright. If there is no connection it is off.Try to turn the output shaft if possible, then you can see if the current flow over the brushes by glowing of the lamp. So you can see if there are shortages in the windings or no connection.

The next issue can be shortage in the commutator. Look to the small slots at the commutator. There can be metall dust of the brushes make a shortage. Clean it with a small knife or tool where you can go through the slot. The brushes are sinter bronce material and the grinding can short coils of the motor if the dust is in the slots. This you can see with the simple lamp setup or more sophisticated with a controllable power suplly with amp meter by turning the motor.

Good luck

Werner
2 September 2022 at 07:37 #612064
Chris Kirby 1
Participant
@chriskirby1
You can get a similar stop start effect from trying to run a dc motor from a switched mode power supply if the motor is taking too much current. If so try a car battery or an old fashioned transformer supply, maybe a battery charger.
2 September 2022 at 08:47 #612072
AJAX
Participant
@ajax
Posted by Chris Kirby 1 on 02/09/2022 07:37:13:

You can get a similar stop start effect from trying to run a dc motor from a switched mode power supply if the motor is taking too much current. If so try a car battery or an old fashioned transformer supply, maybe a battery charger.

I agree with this analysis. Likelihood is too much current is being drawn and so the PSU is resetting itself.

Edited By AJAX on 02/09/2022 08:47:55
2 September 2022 at 10:53 #612088
Circlip
Participant
@circlip
Running a wiper motor in reverse is courting disaster, only designed to run in one direction.

Regards Ian.
2 September 2022 at 11:00 #612090
not done it yet
Participant
@notdoneityet
Posted by Circlip on 02/09/2022 10:53:24:

Running a wiper motor in reverse is courting disaster, only designed to run in one direction.

Regards Ian.

Some, but not all.
2 September 2022 at 12:16 #612096
martin haysom
Participant
@martinhaysom48469
Posted by Circlip on 02/09/2022 10:53:24:

Running a wiper motor in reverse is courting disaster, only designed to run in one direction.

Regards Ian.

i know they should only run one way but the one i fitted to my mill table does not seem to mind which way it turns.

bough new from a Internet auction site made by a German company very common design and cheap
2 September 2022 at 12:33 #612098
Andrew Tinsley
Participant
@andrewtinsley63637
It isn't a wiper motor! It is a window winder motor, designed to run in BOTH directions.

Andrew.
2 September 2022 at 12:44 #612099
bernard towers
Participant
@bernardtowers37738
Can you explain the courting disaster bit as mine on my mill table has been running for over 20 years with no trouble.
2 September 2022 at 16:24 #612114
Speedy Builder5
Participant
@speedybuilder5
Off Topic:- Some wiper motors do not have their brushes perpendicular to the commutator and when run in the wrong direction make the brushes jump up and down ie "courting disaster"..

David's motor is a WINDOW WINDER MOTOR . It would be interesting if David followed others advice and tried a 12 volt battery. If that still didn't work, reverse the 2 black cables and if that didn't work, probably bin them ??
2 September 2022 at 20:03 #612135
not done it yet
Participant
@notdoneityet
Wiper motors draw about 4A, window winders take about 20A. Little wonder it would not work if the power supply was inadequate.
2 September 2022 at 20:20 #612137
David Tocher
Participant
@davidtocher94033
I used a high output switching mode supply when I tested the motors. Using an old transformer PU both the motors work – forward and reverse with no problems.

Thanks for the solution
3 September 2022 at 10:49 #612195
Circlip
Participant
@circlip
Wiper motors? It's a backlash thing. Reversing gearbox for preference.

Regards Ian
3 September 2022 at 11:33 #612203
noel shelley
Participant
@noelshelley55608
Wiper motors with their worm drive produce a heavy axial thrust load, shaft often runs on a ball bearing (1ball). oposite rotation of this type will cause a problem. Noel..
3 September 2022 at 11:36 #612205
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Speedy Builder5 on 02/09/2022 16:24:03:

Off Topic:- Some wiper motors do not have their brushes perpendicular to the commutator and when run in the wrong direction make the brushes jump up and down ie "courting disaster"..

…

Glad Speedy posted that, I recalled non-reversible motors sometimes have offset brushes but couldn't confirm it on the web or in my books.

I believe it's done because offset brushes wear less quickly compared with perpendicular brushes because the leading edge presents at an optimal angle to the commutator. As a result the trailing edge is thin and weak, but that doesn't matter because the motor only runs in one direction. Many winders have ordinary motors, I guess because they're cheaper and their brushes are good enough to last as long as the rest of the car.

Bernhard courted a small disaster when he fitted a wiper motor to his mill 20 years ago unless he checked the brushes. Suck it and see is common in my workshop, but engineers really shouldn't rely on luck! Not a big problem. As a percentage of wiper motors are unsuitable, have a look at the brushes before using one.

Dave
3 September 2022 at 16:56 #612229
An Other
Participant
@another21905
Just a suggestion: I used the motor/gearbox out of an old battery drill – more than enough power. They were 'old', because I couldn't get new batteries to replace the clapped out ones, but the motors/gearboxes were fine (and can rotate in both directions). May be a trifle slow for some users, but definitely faster than hand-cracking the thing.

A simple DC supply/switch makes it easy to use.

They will also work on a lower voltage than designed – I used a 16V motor on 12V, and still had sufficient power.

(edit to add voltage comment)

Edited By An Other on 03/09/2022 16:58:11
3 September 2022 at 18:48 #612239
bernard towers
Participant
@bernardtowers37738
Most wiper motors from the around the 60s and 70s were timed equidistant with the magnets so no problem. Sounds loike a bit of scaremongering.
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