How to tell if an AC circuit ever gets power

[Pascal666]

I have a 120v circuit that is supposed to be energized for about 15 seconds out of a 2 hour cycle. I need a way to tell if it is actually getting energized. Is there a better way than staring at a multi-meter for a couple hours? I'm tempted to put a strand of cat5 wire across it and coming back later to see if it burned up, but I'm not sure how big a mess that would make.

 

[AnalogKid]

What kind of indicator do you want? A light bulb powered by a separate circuit? A flashing LED powered by a battery?

A dual-coil latching relay will hold an armature in place after coil power is removed. You can look at the interlock and see if it has flipped or not.

An AC-powered clock (with a line-powered motor) with a second hand will show how long power was on by the second hand movement.

Where are you located?

ak

 

[Pascal666]

Sorry, I should have clarified, this is for testing purposes, so nothing fancy.

Thank you AnalogKid. Your comment about an AC clock sent me in the right direction. I hooked an AC doorbell to it.

 

[AnalogKid]

Your question was not clear. I thought you wanted a latching indicator so you could see if something happened in your absence, but it sounds like what you really wanted was a signal alerting you in real time to something happening.

If a doorbell is an adequate solution, this will be a huge blow to the 555 / PIC / Arduino / LM317 / CD4017 crowds. Are you *sure* you don't need a web server connecting to an iPhone app through bluetooth?

ak

 

[hevans1944]

I thought you wanted a latching indicator so you could see if something happened in your absence...

I thought so too. I kinda liked the "exploding wire" idea the OP had. That would be pretty "latchie" and it might make a big bang too. Worth a try IMHO. Be sure to use really fine wire, so the circuit breaker doesn't trip before the wire vaporizes.

 

[Pascal666]

Latching, real time, didn't really care, just didn't want to stare at a multi-meter for a couple hours. The doorbell rang. Thanks again!

 

[dave9]

Instead of a wire, how about a detonator and plastic explosives, then put chickens next to it and you can just come back and see if there are any chickens?