Phidgets Forums

Hello Phidget Forums,

I have a bunch of servo controller Phidgets, PN RCC0004 (https://www.phidgets.com/?tier=3&catid= ... rodid=1147).

I supply 24 Vdc power to the board using the screw terminals. I noticed when there are fluctuations servo controller's supply voltage, occasionally, it can cause a rotary servo to jolt (rotate a few degrees in one direction).

Has anyone else noticed this? Has anyone had to protect the power supplies to a RCC0004 servo controller?

--------------------------------------

More details on my set up:

I have a winch servo (Hitec HS-785HB, https://www.phidgets.com/?tier=3&catid= ... prodid=241) connected to the 8th channel of the servo controller. At the time, the servo is not engaged.

The 24 Vdc power is also connected to some 24 Vdc 1 Watt solenoid valves (Clippard NPV1-1C-01-24, https://www.clippard.com/part/NPV1-1C-01-24) through a mechanical relay Phidget, PN REL1000 (https://www.phidgets.com/?tier=3&catid= ... prodid=966).

When de-energizing a solenoid (there's no flyback diode), the winch servo will quickly jolt about 1° to 15° in one direction, either CCW or CW. This is not desirable behavior for me.

I don't think a dip in the supply voltage would cause the servos to behave this way. It seems more likely to me that the changing electromagnetic field from the solenoid is interfering with the servo's signals. Either the internal potentiometer that controls position or the pulse signal wire between the motor and controller could cause unwanted movement if the right kind of interference hits it. If you shield the servo motor and wires behind some metal, or move it far away from the solenoid, do you still see this problem?

Thank you for the response @mparadis.

I also felt I should clarify: the servo only jolts when I de-energize the solenoid, not when I energize it.

The solenoid in question is about 6" away from the servo motor. I also used tin foil to wrap the solenoid, the servo motor, and the motor's wires (which are already a twisted triple). This did not help or alleviate the jolting problem.

How I have solved the problem: adding in a flyback diode between the NO and COM pins of the REL1000, where the solenoid gets its 24 Vdc power. This eliminates the sudden voltage drop on the power bus from the solenoid's back EMF.

What this indicates to me is that the root cause is not magnetic interference from the (far away) solenoid valve, but is from voltage fluctuations on the power bus that feeds the RCC0004.

I guess, I have my problem solved, but think it would be good for Phidgets to add in some sort of voltage snubber to the RCC0004's power input circuit.