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Motor control help.

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toppytop

New Member
I have this circuit attached below. I have built it identical except for the 1.5M pot. All I had was a 1M pot and I am using 18 VAC instead of 12. A couple of problems is that I have to turn the pot about 3/4 of the way until I get a response from the motor. I am using this as a speed control for a model train engine operating at 18 VAC. This other problem is it operates at low speed fairly smooth but as I increase the speed the train eventually stops and the motor just hums. I have read just about everything I could get ahold of on the internet about phase control of a triac. I have not come across how to calculate the R/C circuit for the gate control. Everything you find is for 120 VAC or 220 VAC operation. Any ideas or suggestions for 18 VAC operation. Thanks.
 

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MikeMl

Well-Known Member
Most Helpful Member
What happens if you just connect 18VAC across the tracks? Does the loco run smoothly at high speed?

Run the pot to the point where the loco just starts to move, disconnect the pot an measure its resistance. Reinstall the pot, run it up to the point at which the loco runs fast just before it stalls. Remeasure the resistance. Report back.

Can you borrow an oscilloscope?
 
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toppytop

New Member
Thanks for your reply. I will do as you suggested and report back. I do have a scope, just not real good at using it.
 
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