AC Solenoid Spikes/voltage surge... 5V regulator spikes

Other Hardware Motors, Mechanics, Power and CNC
1

Hello!

I am having issues with voltage spikes from a 110VAC solenoid showing up on the Vcc of the Arduino MCU... causing resets and data corruption :astonished:

The problem:

When I switch on/off the solenoids, there is a spike from the AC which I can see on the 5V board voltage. This spike is causing some problems (resets, data corruption) on the MCU. The relay switch circuit is diode protected... so I know it's the 110VAC voltage spike causing the problems.

I am trying to tackle the problem from 2 angles:

1: Reduce/eliminate the spike on the solenoid coil... I have tried Metal Oxide Varistors (MOV) and TVS diodes (transient voltage suppresor) from ACL to GND. This reduces the spike, but does not eliminate it.

2: Bolster the 5V regulator (to the MCU) in a way that it doesn't pass on the spike to the chip... larger capacitors around the regulator, etc.

I am having problems with BOTH of these solutions...

Does anyone know of the standard way to deal with AC solenoid spikes? I can't find much on the internet...

Also,

Do you know why the regulator doesn't regulate a ~100us spike (+/- 3V from 5V)?

I would really appreciate any help/direction you could provide...

Thank you very much,

Peter

2

A blind shot- zener diode ?

3

It would helpful if we could see a wiring diagram of your whole setup. Do I get that you are using a electro-mechanical relay for switching the AC voltage on and off to the solenoid? Have you tried spark suppression across the relay switching contact? Do you have a reversed biased connected diode mounted right across the relay coil?

If all else fails you might consider instead of using a standard relay, to use a zero-crossing solid state relay.

Lefty