Power Off Timer

Here is a simple idea for a power off timer. Take a clock set it to 12:00(clock with hands the runs on batteries). Plug in a wallwort type power supply. Take a relay and have it connected to the power supply and have batteries in the clock but when the power goes out it closes the contacts for the relay and the clock runs until the power comes back on again. Would this idea work?? I was bored and thought of it one day and want to try it.

It sounds to me like it would work, just be sure to get a NC (normally closed) relay, or else you'll be timing how long your power is on :lol:

If it goes past 12 hours, you of course won't know for sure how long the power is off. You could probably rig a counter with a sensor, like a reed switch to see how many times the hour hand goes past 12 oclock. That circuit would have to be battery run, but I think you knew that