[moldmker]

I'm popping in here to ask a quick question.

On my CNC Centroid mill I have 12 VDC M-function control outputs.

To control my air mist coolant I have one wired to a 12 VDC relay controlling 110 VAC to a solenoid valve.

This worked great for the past year.

This past week I noticed the servos jump when the solenoid valve is activated. And once the XYZ coords were affected.

My manual says the control relay is internally snubbed.
The used relay I added had a diode on the coil which I left in place.
I used shielded cable (grounded at one end) from the control to the used relay.
I used regular extension cord wire from relay to solenoid valve.

I know little of electronics. Is there something that should be placed across the legs of the 110 VAC solenoid coil to help with noise?

Thanks,
Bob

[Al_The_Man]

If the relay coil has a back emf diode, then the other thing to try is a R/C snubber fitted across the 110ac coil, you can buy these ready made or make one from a .1ufd AC-rated cap, and a 330ohm 1watt resistor.
Check the diode in the relays is still functional.
Also operate the relay with the solenoid disconnected and see if you still get the jump.
Al.

[pminmo]

If it is feasable, replace the ac solenoid with a zero crossing solid state relay, then use the signal that controller the 12V relay to control the SSR. Mechanical relays switching currents is just plain bad news for control electronics. The reason is two fold, one contacts bounce. Bounce is like a switch that opens and closes a number of times over tens of milliseconds with arcing happening on each make and break of the contacts. The generates some nasty emi and rfi. The second reason is that mechanical relays are indifferent to what the current is when they switch, so if that bounce occurs on the higher current portions of the ac waveform, the interferrence is worse. A zero crossing SSR will turn on when the AC waveform is a zero, the result is quiet switch event.