SDC2130 v1.5: Brakes released only after a few seconds delay or never

6 years 7 months ago #29528485 by Griffin Baker
Maybe your motors might have a built in mechanism that turns them on and off that maybe causing the issue. Unfortunately we do not specialize in motors, so you may want to refer to the manufacturer of your motors.

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6 years 7 months ago #29528497 by sd1074
OK, I think I solved the problem, and it was a pretty dumb mistake on our side.

The brake solenoids have to have protective diodes. Being an inductive load they result in a voltage spike when the transistor turns off. I am not sure how exactly it worked, but it seems like that spike kept the transistor half-open even when after the gate was set to 0. I measured with an ampermeter: when a solenoid was engaged, the DOUT current was 300mA, when it was properly disengaged, the current was 0, but when it was not disegnaged even after setting DOUT to 0, the current did not dropped to zero, but dropped to ~170mA. This kept the solenoids engaged. And I assume could eventually result in burning the transistors.

The motor controller manual actually clearly states that protective diodes must be installed. After I added them, the brakes are working fine without a delay.

What could be interesting for you is that the previous board (v1.4) was able to sustain those spikes without problems, while the new one, could not. I've found out that the new board (v1.5) has differnet MOSFETs (ON 58 05NG versus RFR3607 on v1.4). That's probably the reason why the previous board did not reveal the problem.

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6 years 7 months ago #29528499 by Griffin Baker
The Dout Driver chip is still the same as before.

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