Relays for AC/DC Auto Start Control Panel

[littleblackdo]

Are there relays which work with both AC and DC? I am design an Auto Start Control panel which will activate on a 24 VDC power signal OR loss of 120 VAC power. I am using relays to accomplish this and I am not very familiar with them.

I was thinking a 24VDC relay connected to the 24 VDC signal. This relay will activate the signal when relay is deenergized ( I still have to figure out how to accomplish this if the DC signal the relay is monitoring is normally not energized). I am just not sure how to accomplish having the start signal with both a 24 VDC signal and 120 VAC. This is supposed to be designed into a simple control panel. Cannot be very complicated due to time restraints (This is a work project, not school). Should I use a rectifier?

 

[anorlunda]

You can use a voltage divider, a diode and capacitor to turn the 120VAC signal to 24VDC. Call that signal B. Signal A is 24VDC present. Then the relay activates when A or NOT B.