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1  Using Arduino / General Electronics / Re: Motor speed controller question from a dummie on: April 25, 2011, 02:24:41 pm
Thanks for all your help folks.  I just ordered the MXA066 controller from Qkits and should see it this week yet.  It looks like it should be easy enough to wire in.

2  Using Arduino / General Electronics / Re: Motor speed controller question from a dummie on: April 23, 2011, 09:47:40 pm
Thank you all for your words of wisdom.

Just to clear up a couple of question marks, the motor is a permanent magnet type, the voltage is indeed 12V in the 1957 Chrysler, and the 8 amp draw is only instantaneous on startup and immediately drops to 4 amps when it reaches speed (less than one second elapsed time).  I've had the motor all apart to resurface the armature and cosmetically restore it.  All appearances inside are fine and the motor is very free.  I do have a service manual for the car, but with this sort of thing they don't go much beyond telling you to replace the motor and see if everything works fine then.

I plan to mount the PWM in an underdash location obscure to all but the greatest scrutiny, and run the controller wires down to the evaporator unit from there.

This is an extremely rare unit of which I have have only become aware of one other in our whole Chrysler 300 Club.  So getting parts or a replacement unit would be next to impossible.  Therefore, if no harm is likely to be done by disconnecting the low speed wire and introducing a PWM on the high speed wire to the motor, I look at the PWM solution as being not only a shortcut to getting around the problem, but also simultaneously giving me more comfortable choices of fan speed.  But, of course, the caveat here is that a PWM has to be able to work on a brush-type motor for this solution to work - and if I read your messages accurately, you all concur that it should.  True?

3  Using Arduino / General Electronics / Motor speed controller question from a dummie on: April 23, 2011, 01:31:27 pm
I know just enough about electronics that I think it's a wonder I haven't died from touching both ends of a flashlight battery, but here is my problem and I'm hoping someone out there can guide me.

I am restoring a 1957 vintage Chrysler dealer-installed air conditioning system in my 1957 Chrysler.  The evaporator unit that mounts on the transmission hump has a little fan on it that has a two speed motor.  But apparently there must be a short in the motor that causes it to run at high speed no matter which speed you switch it to.  When you energize either one of the speed wires the motor runs, and the other speed wire also tests energized.  Even if both speeds were working fine, you'd really want one somewhere between the two, so I want to go for a better solution than fixing what may be wrong in the motor.

My plan is to put what I understand is called a PWM in one of the speed wires and disconnect the other one.  That way I will have infinite control of the range of speed for the fan.  Now, all the info I have dredged up on PWMs says they are made to work on brushless motors.  I don't know if brushless motors were even born in 1957 yet, but this certainly isn't one.  And for the life of me I can't figure out if a PWM is supposed to work on a brush type motor as well.

This 12V motor is drawing about 8 amps on startup and 4 amps running.  Can I buy just any old PWM of perhaps 10-15 amp capacity and hook it up inline to this motor to control the speed?  Or do I have to use use a resistor type controller for this brush-type motor?  What should I look for and where should I buy one ready to plug in?
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