Power on? Hard to be sure.

I had hoped to use the Vera to send shutdown messages to other devices in the house if the power went out, but it turns out Vera doesn’t track whether the power is on or off (it IS plugged into a UPS, so that would kinda limit that).

My first solution was simply to trigger some Vera events based on a “vendor code” generated by the alarm system, after all it switches to battery power when the power goes out.

No good. Turns out it doesn’t kick that vendor code out to Vera – I can get it to warn Vera when a “trouble” status is triggered (an “AC FAIL” generates a trouble indication), but it might be a different trouble (“Low Remote Battery”, “Communications Issue” etc etc) and that doesn’t sound like a reliable kludge.

The vera forums discuss using a wall wart 12vdc power supply, a relay and a wireless zwave door/window contact to monitor the AC Status – it’s clever – the wall wart voltage triggers the relay keeping the alarm circuit closed, as soon as mains power drops the relay loses power and breaks the circuit, triggering the zone.

I can do that, but using our alarm system to instead of a zwave door/window contact.

simple ac sensor

As luck would have it I have a pile of generic 12vdc wall warts, a number of 12v security relays and I happened to have a zone free on my alarm system.

About 30 minutes of monkeying around, running wire back to the alarm system and making sure the new “AC Sensor” was plugged into the same circuit as my home automation gear and we were away to the races.

I’ll have to double check the programming in our alarm system to make sure it doesn’t trigger a burglary alarm when the power drops, but otherwise it seems pretty slick.

I’ll do a little quick programming in Vera, and some monkeying with ssh and I should have something that saves our hardware from an unexpected shutdown.

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