I am currently trying to finish up a DIY project I've been working on for a while: Building an electric potters wheel. I acquired a treadmill and salvaged quite a few good parts from it, and thought this would be a great way to put it to use. Unfortunately when I got everything together, and after a few tests I committed a terrible crime: I dropped a washer on my MC-60 motor controller board. As you guessed, on my next start-up there was magic smoke everywhere.
So I have all the physical assembly completed, and a good condition treadmill motor without power supply. So I'm venturing into salvaging and building my own, not spending $50-$100 on a new board if I can help it.
I have been doing quite a bit of reading over the past few weeks and came to the conclusion that PWM supply offers the most consistent torque, and this was what I was concerned about. I don't want the thing to be choppy and low torque, so I'm going to do some physical reductions with pulleys/gears to be able to maintain a decent amount of torque on the motor.
I've completed my PWM circuit with the quick help of Netduino isolated with Opto to drive mosfets. Everything seems to be fine, yes I'll have to adjust components to varying voltages as time moves forward.
I know I don't have to drive this thing with full 90vdc to get the small amount of toque/rpm I need correct? I mean it's a pottery wheel, not a lathe. I figured I might need 30-40vdc max, or is this a bad assumption? Will this drastically lower my torque to an unusable level? I really would like to avoid dealing with 90vdc PWM, that seems like way overkill.
My theory on the power supply is I could simply use a transformer to reduce a 110vac voltage to say ~50vac (or whatever necessary) and then rectify and smooth this resulting DC voltage to a usable limit. Then drive this through the MOSFET, to the "clutch" (which helps further smooth any ripple), to the motor. Am I headed in the right direction or am I under-thinking something here? I just really don't want to waste anymore money on components until I can be certain it's the correct way to go. I also don't want to waste money on a control board that is complete overkill for my needs. All I need is simple on/off with a little bit of speed control, nothing really specific.
Thanks for any help.
Motor Specs: Permanent Magnet DC Motor Electrical Rating: @130vdc 2.5hp 6700rpm 18amps Continuous Duty @95vdc 1.5 hp
Just realized it would probably be better to maintain a higher voltage to keep as much torque as I can, and adjust the duty cycle. Rather than adjusting the voltage to say 60vdc and then PWM that..