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| Need Help Wiring DC Motor with PWM |
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| snub:
I found an interesting wiring diagram on the interweb showing how to control a DC motor with a SPDT switch and 2 automotive type relays. The motor is the kind where the direction of rotation is changed by reversing the polarity of the 2 input wires. The way it was wired seemed odd to me, grounding through the switch and power was going to 2 terminals on the relay. Anyways, I hooked it up as per the diagram, and it works just fine. So then I'm thinking I'd like to hook up a Pulse Width Modulator to control the speed and wondering why I can't use a single PWM straight off the power supply. I didn't think it would work and I was right. It doesn't. At least not how I have it wired. I even tried a second PWM from a different manufacturer and same thing. Motor runs at full speed, won't slow down. I'm wondering why it doesn't work and if there is another way to wire it. First diagram is the one I found at Burden Supply, the second is how I wired in the PWM. . |
| PK:
Basically you need to PWM the power going to the motor, but NOT the power going to the relay coils. So wire both 86 terminals of the relays to the +ve terminal of the battery (and only to the + terminal of the battery). PK |
| snub:
Thanks for the reply PK, but I'm not understanding. Are you saying to supply PWM regulated to the #87 terminals and battery voltage to the #86? |
| RobWilson:
like so Snub As PK mentioned the relay coil will have some issues being supplied with a PWM supply :zap: Rob |
| snub:
Well, back to the drawing board. I hooked it up as you showed, but still no love. Motor runs at full speed. I tried another PWM with the same result. I even reversed the terminals at 86 and 87 just to be sure. |
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