Using the same cord to power a relay and the arduino

I'm currently trying to design a thermostat for refrigerators/freezers. I have a solid state relay to control power to the cooling element. I had considered trying to power the cooling element as well as the Arduino it self with the same power source, which in this case is just an extension cord. Can I do this with fear of dying?

sgillespie: I'm currently trying to design a thermostat for refrigerators/freezers. I have a solid state relay to control power to the cooling element. I had considered trying to power the cooling element as well as the Arduino it self with the same power source, which in this case is just an extension cord. Can I do this with fear of dying?

I assume you meant to say "without fear of dying".

The transformer providing power to the Arduino and the SSR should be sufficient to isolate the Arduino from the dangerous household current.