I'm trying to create a smarter controller for my hydroponic systems. I have an arduino controlling a sainsmart mechanical relay. The load on the relays are 24 VAC orbit sprinkler valves. Everything is powered from the same 120VAC circuit using different wall wart transformers.
The problem is that 30% of the time the arduino resets when a valve is triggered. This happens whether or not the relay board is fully optically isolated or not. But, this does not happen when the arduino is powered off a 9 volt battery.
I'm guessing that the relay triggering is sending power spikes into 120VAC.
Should I setup a snubber circuit, and if so, what are good specs? Should I ditch the mechanical relay in favor of the below SSR?
The mechanical relay board: http://www.sainsmart.com/8-channel-dc-5v-relay-module-for-arduino-pic-arm-dsp-avr-msp430-ttl-logic.html
The solid state relay board: http://www.sainsmart.com/8-channel-5v-solid-state-relay-module-board-omron-ssr-4-pic-arm-avr-dsp-arduino.html