Hi folks, love been running a sander with an mc 60 for 10 years and I smelled the smoke today and it's a goner. I have an mc2100 and see there are ,new from 10 years ago ,signal generators that run the 2100 from a pot and that's great,but in looking around it seems the 2100 can be temperamental in metal dust environments and the mc60 /scr is more"robust" and better for my application. Does anyone know why we can't make from scratch an scr that is better and le$$ than kb drives on our own? I have some chunky scrs from an instant water heater that seem they could handle 90vdc treadmill motor?

 

Thge disadvantage with the MC60, SCR bridge ver. is that they 'cog' at low RPM's.
The MC2100 is HF PWM, so much smoother control down to zero rpm.
The SCR's are not critical, fit a higher rated SCR and fuse properly.

 

Thank you Max,I found in my parts an mc 1200 and 2100 that from looking around seems it would work with a pwm generator,also I think I read somewhere you make those.I do have a breadboard with a 555 pwm on it and I may try to adjust it to work, but I'm not even novice at this. Do you have any of those built to sell in case mine doesn't pan out?

 

I have a few boards left, if needed.
If you put one together, e.g.555, it has to be very close to the 20hz needed,
Also check the resistor value into the opto on HD2 pin4

 

Max, I have been using the pwm from the treadmill for the time being,I did pull out my breadboard and will try to build the pwm when I get a minute. I have my mc1200 in a container with a lid to prevent dust from getting on it and thought I'd keep an eye on overheating issues and found the ceramic resistor heats up quickly if power is on to the board. The resistor heats much less if I have the motor driving ,the faster the cooler. I have read some threads asking about this same resistor heat issue,it will also heat up if I'm running motor at a low speed. I've read this resistor is part of the 5v logic supply,but could it be part of the dc motor supply due to my observations?
I also have thoughts on why folks are using these mc boards at all when they are designed to supply lift motor duties,soft start and what not when all most of us want is around 90 volts dc with pwm to run the motors. Are these also considered a transformer less power supply? What is stopping anyone from building a circuit of a rectifier ,some smoothing and ,I guess a mosfet h bridge and freewheel diode to go with the pwm like the ones you make to control the duty cycle? I'm no expert though,just seems to me we don't need more than half of what can cost over $200 if we buy mc whatever's online.
Sorry to get long,but there's guys with newer vids out tinkering like I did 14 years ago and they're being called kings of treadmill motor controls when the best info I've read in all that time has all come from you.

 

I have just acquired the boards from scrapped/free pick-up TM's, so has not cost much. Those that are in the market for selling them usually thy are intended for those that require a replacement to get their TM working.
The MC2100's are transformer-less for the motor & lift circuits, but they do have a 12vdc transformer isolated supply for the isolated PWM circuit etc..
The 7W resistor should not change much, it feeds a 12v Zener circuit.
I agree if you have to pay off-the-shelf price they can be a bit pricy!
I have considered building one similar from these scrapped ones, but bi-directional.

 

Reverse would be great to have, Ive seen threads talking about ways of adding that for lathe guys. I think there would be interest in the "Max 2100".I read about your pwm in a forum that you weren't even at.