SystemsGuy
New Member
Hey guys - reviving a dead project I gave up on long ago. I'm trying to design a circuit that takes specific actions based on duration power failure. Pretty straightforward, it's a 12vdc circuit, and I want to be able to take different actions depending on the duration of the power loss at 15 second intervals up to one minute. So action "a" if < 15 seconds, "b" > 15 < 30, etc.
Complicating this is the fact that the power supply I'm trying to measure outage on is the same one that powers the circuit, and that I don't have the ability to add a battery to the mix - even something as basic as a RTC would make it non-viable. It's also got to fit into a very small physical footprint of about 3cm x 3cm x .5cm. I started this with a tiny13 (dating myself I guess!), but never managed to figure out how to make it survive the outage and then "know" that it both "had" and "how long" it had been out.
I'm a digital sorta guy, so trying to get my head around how to accomplish this - I was thinking a capacitor with a know decay rate, or something along those lines, but rapidly got out of my depth.
Any clever ideas? I'm not really concerned about loss > 1 minute - would be "nice" to know that there was a loss > 1 minute, but not really critical.
Thanks!!
Complicating this is the fact that the power supply I'm trying to measure outage on is the same one that powers the circuit, and that I don't have the ability to add a battery to the mix - even something as basic as a RTC would make it non-viable. It's also got to fit into a very small physical footprint of about 3cm x 3cm x .5cm. I started this with a tiny13 (dating myself I guess!), but never managed to figure out how to make it survive the outage and then "know" that it both "had" and "how long" it had been out.
I'm a digital sorta guy, so trying to get my head around how to accomplish this - I was thinking a capacitor with a know decay rate, or something along those lines, but rapidly got out of my depth.
Any clever ideas? I'm not really concerned about loss > 1 minute - would be "nice" to know that there was a loss > 1 minute, but not really critical.
Thanks!!
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