power for a wiper motor

[John WeightParticipant @johnweight34532]

ideas needed

[John WeightParticipant @johnweight34532]

Good evening gentlemen, I am looking for a suggestion on the best way to supply power to drive a 12 volt windscreen wiper motor other than using a car battery. I'm thinking along the lines of using maybe something like one of those 3 pin plug type gadgets that are used for small electronic gismos, but really have no idea whether this is feasible, any suggestions or other ideas would be most appreciated and gratefully received. many thanks, John

[NigeParticipant @nige81730]

This thread might help

http://www.model-engineer.co.uk/forums/postings.asp?th=123769

Nigel

[John HaineParticipant @johnhaine32865]

See this thread:

**LINK**

[OldironParticipant @oldiron]

Agreed, use the PC power supply 12v/5v/3.3v outputs. Dead easy to mod. You don't even have to open the case. I run all my power drives and my dro's from one. Have added a USB port to mine so I can power the tablet for the TouchDRO readout.

Gary

[Howard LewisParticipant @howardlewis46836]

Have not read the links, but bear in mind the current draw of the wiper motor, when it presumably powering the traverse on that particular machine. It might exceed the capacity of the "Three pin plug" type power supply, but no point in discovering that the hard and expensive way.

Not all diminutive power supplies are DC, some are AC, and the output is less than an Amp! Many are unregulated, so as the current draw increases, the voltage falls.

Even a simple Battery Charger is unregulated, but would probably suffice, and be capable of delivering 6 Amps; which might suffice.

Howard

[Antony PowellParticipant @antonypowell28169]

You'll Find most 12 volt wiper motors are fused between 10 and 20 amps

Tony

[John HaineParticipant @johnhaine32865]

To answer your original question, no a wall-wart will not drive a wiper motor, you will need a suppy that can comfortably deliver over 10Amps to handle the stall current. One option is a PC power supply but they can be tricky to use sometimes. A better and perhaps cheaper option is this sort of thing:

**LINK**

Absurdly cheap from China. I've bought a couple of this sort of supply and they are perfectly fine.

[duncan webster 1Participant @duncanwebster1]

These Chinese power supplies do look like very good value, but be aware that they have not necessarily passed UK electrical safety tests. I bought some LED lamps that were potential death traps. At the very least make sure that the outer casing is earthed.

I've read somewhere that you have to load the 5v output of a computer PSU to gets regulation on the 12v. Can someone who knows what he's talking about confirm?

[Jeff DaymanParticipant @jeffdayman43397]

In the past I've used large model train power packs to drive 12VDC wiper motors when a car battery wasn't available but mains voltage was.

They usually have electrical approval stickers from UL or BSI as well. Seen lots of them at model train flea markets and yard sales for reasonable money. JD

[Frances IoMParticipant @francesiom58905]

Many of the older computer PSUs would have a minimum drain on the various supplies that was needed for the voltage regulation to work so yes for light loads you needed to add a load(high wattage resistor) to reach that minimum loading Often the 5V line needed to be established before the 12V line was switched on.

Edited By Frances IoM on 23/06/2017 08:39:06

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 23/06/2017 00:22:22:

I've read somewhere that you have to load the 5v output of a computer PSU to gets regulation on the 12v. Can someone who knows what he's talking about confirm?

.

From my archive of 'that should come-in useful one day' links:

**LINK**

http://www.instructables.com/id/ATX–%3E-Lab-Bench-Power-Supply-Conversion/

MichaelG.

[richardandtracyParticipant @richardandtracy]

I tried a PSU for my 12v electric screwdriver. No go. The 5v line is the one where the voltage is controlled, and unless there is a significant load on that, the psu doesn't try to control the 12V line, and simply switches off to protect itself. Not very useful when using significant amounts of 12V power. I had a 2 ohm, 10w resistor across the 5v line, but in comparison to the screwdriver draw, it was woefully inadequate. Tried 2 of those resistors in parallel, so drawing 20W, Still inadequate.

I now use a partially dead car battery for my screwdriver – it's a lot less dead than my Ni-Cad's for the screwdriver and it doesn't go flat on screw 10, or 300 for that matter. It's irritating lugging a 33AH lead acid battery around on a 3m lead, but it uses stuff that would otherwise be rubbish, so I'm happy.

Regards,

Richard.

[egaParticipant @ega]

richardandtracy:

I know very little about this but might the problem lie in your choice of PC PSU? I have half a dozen of varying ages doing nothin here.

[Frances IoMParticipant @francesiom58905]

There has been continuous development in these switched mode power supplies over the 25+ years of the IBM PC design – many used the same basic circuit + integrated control chips available at the time – also as hard drives etc developed the need for high current 12V supplies seems to have diminished and the 3.3V line became the dominant supply

[SillyOldDufferModerator @sillyoldduffer]

All bets are off if you use a computer PSU to power anything else. A computer power supply is somewhat complex bunch of switch-mode power and control circuitry. No consideration whatever will have been given at the design stage to the possibility that it might be used for another purpose.

I've tried to repurpose two, both unbranded generic types. The output specifications and physical appearance were identical. One 'just worked', the other I eventually gave up on. Using them is a gamble, not engineering. If yours works, hurrah, if it doesn't no tears please.

Dave

[I.M. OUTAHEREParticipant @i-m-outahere]

For what its worth you can buy a switchmode power supply that will do the job off ebay cheaper than a pc power supply .

If you have some experience with electronics you could pick up something from a computer shop or off the side of the road that is still working and check it over yourself , look for bulgeing capacitors and clean the dust out .

They are fairly robust items

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