MC2100 ramps up to full speed then stops

Thread Starter

squash4

Joined Apr 14, 2023
6
I've been using this MC2100 in conjunction with a pwm circuit I built, and had been using it successfully for a time on a bandsaw. I must have pushed it a little too hard when resawing a log, as the motor suddenly stopped in the middle of the cut. The behavior afterward was that turning it on resulted in the motor ramping up to full speed and then stopping. Looking around on this forum it seemed like I blew out the mosfet, Q4 on my board, and I checked it and it was shorted. I replaced that, but I still get the same behavior (on a scope the voltage output ramps up to about 100V and then slowly decays).

Not sure what to look for now, nothing else seems to be shorted on the board. The LED blinks twice then pauses, which according to this video indicates a wire has become disconnected, which is a bit unhelpful.

Any help is appreciated.
 

Thread Starter

squash4

Joined Apr 14, 2023
6
I got the new SCR in, and the motor controller is working now, albeit in a strange way. The motor will run for about 5s, and then shut off for a couple seconds before turning back on. Another odd behavior, if I push the motor hard (resawing about 8in seems to do it) the motor shuts off, and the led on the controller board shuts off. It will then refuse to turn back on for a while, but if I leave it alone for a few minutes and plug it back in it will start working again.

It's usable in its current state, but it is a bit annoying, and I'd like to be able to use it to it's full potential. I appreciate the help so far.
 

Thread Starter

squash4

Joined Apr 14, 2023
6
Another thing, I was just running the motor and it seemed to stall out, I turned it off and then back on and the motor immediately ramped up to full speed and I had to cut the power. Now when I turn it on I can hear the motor start to spin but stop immediately.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
If you turn it on and it starts to run before any input signal, then it sounds as though the HV DC is already present i.e. has ramped up or turned on.
It could also be the driver IC, MIC4427
 

Thread Starter

squash4

Joined Apr 14, 2023
6
Put this project down for a while, as that last incident blew out the mosfet.

To be clear, it doesn’t run without pwm signal.
Popped a new mosfet into it, and it’s back to proper speed for a few seconds, turning off for a few seconds, then repeating the cycle.

Also, it only seems to do thiscycling under load, testing on the bench it seems to run normally. As far as I can tell nothing is shorted now.
 
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