Thread: Frustrated: Power Supplies & Wiper Motors

Tweet

Hey guys-
I am VERY frustrated at this point. I'm trying to wire up a wiper
motor, using the parking mode, with an ATX power supply. I have an
1157 automotive bulb running on the +5v line to keep a load on the PS
at all times. That works great. If you aren't aware- the wiper motor
runs on 3 pins... +12v, ground, and another ground for the parking
switch (returns the motor to the home position). So you wire the +12v
and ground up permanently, and use the 3rd pin/ground as a switch to
turn it on and off. When you switch off that 3rd ground, the motor
returns to the home position. The motor works great. Here's the
problem...

I turn it on, let it run for a few seconds/revolutions. When I
disconnect the 3rd ground wire- the FIRST TIME it works as it should-
motor returns to home position, and ATX PS stays on, bulb is still
lit, everything it great. Now here's where the fun begins... after I
disconnect it the first time- SOMETIMES I can get it to switch on/off
2-3 times in a row. However, most of the time, when I connect that 3rd
ground back to the motor/pin, it shuts the entire thing down- power
supply, light bulb, everything. Like I said, sometimes I do it and
it'll go ahead and run the motor again, but the next time I re-connect
it, it stops everything dead in it's tracks.

This is the 2nd ATX PS I've tried (different brands, sizes, etc) and
get the same exact results on both of them. I'm convinced it has
something to do with the PS, and NOT the wiper motor (I know this
because I tested it out on a 6v battery and it works perfectly fine).
Can someone please help me on this? I'm about to throw the whole
thing out the window! LOL...

do you have a power resistor wired across the PS in order to maintain its power on state?

No, I took it off as that wasn't working. I replaced the resistor with the automotive light at 5v instead- supposed to work just the same...

Originally Posted by Specter

No, I took it off as that wasn't working. I replaced the resistor with the automotive light at 5v instead- supposed to work just the same...

when you turn the PS on is the motor connected/switched on, or do you turn on the power supply then turn on the motor?

Let's see... Normally the +12v and -12v permanent ones are wired to it already when I turn it on. Then I connect the 3rd -12v pin for the parking switch and the motor starts to run at that time. The motor won't run without that 3rd pin connected.

I've tried it where it's all connected right from the getgo- and it works right off the bat. I disconnect the 3rd pin, and it returns to the home position. When I RECONNECT it, that's when it shuts down on both ways...

maybe its because the load of your light is too low

remember these units are designed to protect PCs, and a sudden power level drop could indicate a problem.

What is your light wired across? I think you should usually use the 3.3V circuit

consider the power drain step from off to on without the motor is quite small, yet the power step from motor on to motor off is quite steep, if the light/resistor was drawing more power then it may be better able to maintain the power on

That's a great point. I have it wired to the 5v wires right now. I can go try the 12v and see if that helps it any...

ok, hooking the light up to the 12v... obviously the bulb was brighter right from the start. I touched the parking switch to the ground, bulb got brighter, motor ran. I removed it and the thing shut down in it's tracks- PS and all. It didn't stay on like it did when using the 5v on the light and return to the home position- it just shut the PS down immediately.

Then I tried the light on the 3.3v line. As soon as I touched the parking switch to ground, it shut down. It didn't even run the motor. It shut the PS down right away when I connected the parking switch...

So I moved the light BACK to the 5v line... same results as before- light came on, then I touched the parking switch to the ground, motor runs. I disconnect it, motor returns to home position. This time I got it to do it again- reconnected it, it ran, disconnected it, returned to home position. The 3rd try I connected the parking switch to ground, the PS shut down.

Any ideas?

think I got it figured out...

There's some sort of mechanism in there that would shut it down if I reconnected too soon... so if I waited 30-60 seconds in between connections, it works perfectly!

Now- I just need a time delay relay or something. Ideas? I need something to go from 30 seconds to about 2-3 minutes... I was thinking of hacking a fog machine timer, and hooking THAT up to a 120vac-->12vDC relay, but I'd prefer something cheaper/easier. Ideas?

I would suggest dumping the switching computer power supply and changing to a regulated 12v linear power supply. They're not very expensive and it will make your life a lot easier.