JRK 21V3 with a switching power supply

I am using a large Gearwurx servo that uses a JRK 21V3 motor controller and I am trying to drive it with a Mean Well 12VDC/4.5A switching power supply. I am having a problem with the servo causing the power supply to shut down. When the servo moves, the voltage on the power supply line varies from 6V to 15V according to my scope, as though the regen power from the servo is causing massive noise on the power supply line. This noise is causing the power supply to shut down.

I tried a parallel flyback diode across the power lines and it had no effect. I put in a large series diode and the power supply was happy, but running the servo for about 2 minutes caused the motor controller to blow. I guess this is from the regen power from the motor having nowhere to go.

I was told that a large electrolytic cap across the power lines might help. Do you have any suggestions for fixing this problem?


Hello Doug,

We responded to your earlier post before we noticed this one. You can find that response here:


Thanks, Nathan.

I got some big capacitors, from 33uF to 4700uF, 35V and tried them out. The biggest 2 would allow the servo to run continuously in a smooth back-and-forth movement with no issues, but if I try a snap movement from one end to the other, the power supply still trips. I even paralleled the 2 largest caps to get 8000uF and it still tripped during a snap movement.

Throughout all of this, I have been watching the PS voltage on a scope and have not noticed a significant difference in the traces between using the caps and no cap.

I was told a bleeder resistor across the cap might help.

Any other suggestions?


A bleeder resistor might help, but that would draw a near-constant amount of current from the circuit. A transient voltage suppression (TVS) circuit is similar, but only draws current when the voltage exceeds a threshold. You might try characterizing the voltage of the spikes that cause your supply to trip with your oscilloscope. You could then select a TVS that has a threshold voltage between your nominal supply voltage and the voltage at which the supply trips.