It will only work one way though, that is for sure!
I am having the same problem; can you give a little bit more information what you mean by "putting diodes on every connection going back to the arduino"? Thanks.
To all that have weird characters on LCD screen when you run 117 Volts from a relay using the Arduino!This is what I found. Put a 470 uf electric capacitor across the SIGNAL pin on the relay and ground. That fixed all the issues for me.I driving the relay with a separate power supply, which didn't work which led me to believe It could be the signal pin and sure enough it was. Hope this works for everyone else having the same issue. 1/11/2018
show on pic please!