Advice to reduce noise on slot car controller SOLVED

I am making a digital slot car controller. After maybe an hour of track time, the main power MOSFET (M1) died on me. Putting it on the scope with the motor running, there are transient spikes in the 50-60V range. The motors operate at 12V and can draw anywhere from 1A to 3A continuous, 8A peak.

I added C4 across the power leads to hopefully smooth out the power across M1, but it doesn't seem to help much. Any advice on how to reduce the noise, or at least protect the M1 MOSFET? Feel free to point out anything else I may have done wrong.

by SgtSnyder2
February 21, 2023

Simplified circuit:

by SgtSnyder2
February 22, 2023

1 Answer

Answer by FrankyDee

Have you tried a snubber network parallel to M1? And a faster diode D1 than 1N4004?

ACCEPTED +1 vote
by FrankyDee
March 02, 2023

Thanks for the reply, this is exactly what I ended up doing, and it works exceptionally well! I picked up some MUR460s, and put one across the motor leads and the other across M1. No more spikes, and only slight noise at M1s drain, miles from concerning. The voltage everywhere else is rock solid.

by SgtSnyder2
March 09, 2023

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