What AMP power supply for windscreen wiper motor

[petro1headParticipant @petro1head]

Looking to buy a power unit for my X axis power feed project. However I have no idea what current draw the wiper motor uses and need an idea before buying a power supply

Edited By petro1head on 07/01/2017 17:41:15

[petro1headParticipant @petro1head]

[not done it yetParticipant @notdoneityet]

Voltage might be important! 12 or 24V?

[petro1headParticipant @petro1head]

Opps, yes indeed. 12V

[richardandtracyParticipant @richardandtracy]

10 amps seems a suitable Max.

Do you have an old computer? The PSU can usually do 10A at 12 V. Needs a few extra components to make it work. Currently I'm converting one to power my 12V electric screwdriver now the battery has died. Needed parts cost £1.71 from Maplins. It's worth doing a search on how to do it – there's a lot of info on the web.

Regards

Richard.

[petro1headParticipant @petro1head]

So something like this would do it? – **LINK**

[richardandtracyParticipant @richardandtracy]

I'd be very surprised if it draws much more than 120W, so yes, but would suggest waiting for comments from others before splashing any cash on it.

Regards

Richard.

[petro1headParticipant @petro1head]

I think my main concern is the initial current draw at switch on

[Martin ConnellyParticipant @martinconnelly55370]

If you keep the battery in the system you can use a lower current power supply. Since you do not run the feed continuously the power supply will top up the battery when the power feed is off. With this in mind a cheap 12v battery charger may suit your needs. If you are not able to use the battery shown then a smaller lead acid battery could be used. 

Martin

Edited By Martin Connelly on 07/01/2017 18:56:38

[petro1headParticipant @petro1head]

Did a check and on initial start on the draw is just over 10A settling to a steady 6.5A

[not done it yetParticipant @notdoneityet]

There might also be an electric window winder that could be considered (to replace the windscreen wiper motor) – somewhat more powerful. Worth considering before buying an under-powered wiper motor system?

[BWParticipant @bw]

I have also seen electric motors used to raise/lower car seats mentioned as being useful for this purpose.

[petro1headParticipant @petro1head]

Posted by not done it yet on 07/01/2017 19:39:53:

There might also be an electric window winder that could be considered (to replace the windscreen wiper motor) – somewhat more powerful. Worth considering before buying an under-powered wiper motor system?

 

 

 

Uhum **LINK**

Edited By petro1head on 07/01/2017 20:00:32

Edited By petro1head on 07/01/2017 20:03:51

[John HaineParticipant @johnhaine32865]

You could arrange the speed control to give a soft start to reduce the switch on current. I have a feeling that w/wiper motors are much over-specified for this task actually and you could use a much smaller motor, given that there could be quite a step down ratio to the leadscrew. Look at Mike Cox' version on his website.

[petro1headParticipant @petro1head]

Just Posted by John Haine on 07/01/2017 20:06:08:

You could arrange the speed control to give a soft start to reduce the switch on current. I have a feeling that w/wiper motors are much over-specified for this task actually and you could use a much smaller motor, given that there could be quite a step down ratio to the leadscrew. Look at Mike Cox' version on his website.

Well I have already gone with a wiper motor. See my link above

[John BaronParticipant @johnbaron31275]

I built a window screen wiper motor table drive quite some time ago. I got mine from the local scrapyard for the cost of taking it off the scrap car it was attached to. Actually I got two, one left hand drive and one right hand drive. Neither draw more than 2.5 amps at 12 volts on full load. Mine normally takes about 2 amps and runs at around 8 volts. I actually run it from an old variable voltage lab PSU, which has built in voltage and current meters. I used a tumbler gear mechanism to provide both reversing and disconnection so that the right handwheel can be manually turned.

For a build log.

http://www.homemodelenginemachinist.com/showthread.php?t=23130

Edited By John Baron on 07/01/2017 20:36:16

Edited By John Baron on 07/01/2017 20:36:42

[Ian PParticipant @ianp]

Posted by petro1head on 07/01/2017 19:19:24:

Did a check and on initial start on the draw is just over 10A settling to a steady 6.5A

Out of interest, how did you measure the peak current, was it with an oscilloscope?

If you are quick enough or brave enough, you could measure the short circuit current with an ordinary digital or analogue meter with the motor stalled. I would not be surprised it it was more than 20A.

I used car wiper motors on several projects (20 or more years ago) and found that some modifications became essential. Most wiper motor only rotate in one direction and the gearing and bearing arrangements are optimised for that direction. One I used had now provision for the motor spindle (with its integral worm gear) to handle the thrust in the reverse direction. I have also come across the tooth form on the worm and pinion being assymetrical (like a buttress thread) so the gearing efficiency is significantly different in the two directions.

I have no knowledge of the internal design of the wiper motor you have used and its more than possible that the potential problems dont exist in yours.

One other point is that the method of obtaining the two speeds is often by using a third carbon brush positioned so that it uses fewer of the armature windings. Less copper means less resistance so the motor current is much higher resulting in the increased speed. The motor efficiency suffers at the higher speed but the vehicle electrics can cope with it.

Finding a power supply with a PWM output with a high enough current rating to cope with a relatively high current motor might not be easy

My choice would be to use the slow speed brush connection but use a higher than 12V supply (say 15 or 18V)

Ian P

[petro1headParticipant @petro1head]

I don't have access to an oscilloscope. I used a clamp meter attached to my multimeter.

I will be using a 40A rated PWM.

For the number of times I use the mill if the motor lasts a year and then has to be replaced that's not a problem. They are cheap enough.

[Ian S CParticipant @iansc]

I use an old Lucas wiper motor for the power feed on my mill, I extended the shaft through the worm wheel to take a sprocket, ten tooth to motor, 20 tooth to mill, joined with a bit of bike chain that is loose enough to be lifted off for manual feed. The motor works ok in both directions, and I run it on 18volts. I have three switched speeds using resistors. It's been going some thing like 20 years, and shows no sign of giving up. These motors will take up to 100% over voltage.

Ian S C

[GarthParticipant @garth]

One should take care in reversing windscreen wiper motors, they are designed to run in one direction only in most cases. Brush position can give excessive arcing with reverse rotation

Door window motors would be more suitable.

Due to high gearing of these motors 10 Amp power supply would be more than enough.

[Ian S CParticipant @iansc]

The old (1960/70) Lucas motors seem quite happy in either direction, these ones also have wound stators instead of the modern ones with permanent magnets. Another motor that I run is from a garage door opener, it's a 36 volt type, it is the motor on the hoist above my lathe.

Ian S C

[AjohnwParticipant @ajohnw51620]

Having worked for Lucas it's pretty certain that a wiper motor will be rather robust. Far more so than window winder motors or seat adjustment ones. Not that there is bound to be problems when those are used. Very modern stuff may be a bit different thanks to electronics.

If it can be run at various speeds I'd be inclined to use the fastest one and gear down if needed but just try pulse width modulation initially. 40 amp is probably a sensible size for the modulator but if in doubt it might be a good idea to measure the stall current.

It's possible to find ones for 24v as well. Often expensive as they are mostly used on artics but these can also be cheap. I'm hoping one will do for a power lift on the head of my Dore Westbury – when I can get at it and have the time. There is also a very watty 24v switch mode supply to go with it. Part reason for 24v is maybe making use of cnc at some point. Just on the off chance that I do.

John

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[Gary WoodingParticipant @garywooding25363]

As Garth has mentioned, many modern windscreen wiper motors are designed to run in one direction only. Instead of positioning the brushes radially they are set more tangentially so as, I suppose, to provide a contact area larger than the brush profile area as well as reducing the overall dimension. When run in reverse, the brushes move slightly and start to wear a new arc, thus reducing the designed contact area in forward and reverse. And thus reducing the power very noticeably.

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