Need idea for a 12v source monitor

I have about 19 doors at my office that are access controlled with magnetic locks. The locks run on 12v. Today, the power supply that powers the locks died and all the doors were left unsecured.

I am looking for some ideas to monitor the 12v output of the new power supply and if it fails, automatically switch over to a backup power supply. I’m kinda kind of stuck on which is the best way to handle something like this. I was thinking a couple of Shelly 1 relays and a HA instance could probably do the trick. I know people here are way more creative so what ya got for me?

Thanks in advance.

Ignore this.

An esp running through a voltage convertor (12v to 5v) will become unavailable when the power fails.

You can detect that and switch the other power supply on.

Damn. I seem to have replied to the wrong post.

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With a Sonoff R1 you can measure the current or power usage. Whenit drops below a treshold you power supply failed. If you want automation, just buy a second Sonoff R1 with a 12V power supply an swith on that one ( remote) after switching off the first one.
Havinng both Sonof units on could blow also the second power supply if you have a short in your first power supply.

Probably many other solutions are available.
The Sonoff monitor works for me as a check for the pump of my floor heating system is running.

I am assuming that your HA instance will stay up on power fail? You could use an ACS712 based module - say running off a ESP32 with battery backup for redundancy?

Everything is on a battery backup. I am not familiar with an ESP32 or an ACS712. I was thinking a Shelly 1 connected to the 12v output of the PS. Then another Shelly 1 connected to a backup PS. Then make a rule that if Shelly 1 (original PS) was not detected, switch on relay of Shelly 1 (backup PS) which would then provide 12v to the system again.

Pretty well what I suggested then.

Have two 12V power supplies. The output of each supply goes to the anode of a Schottky diode (with appropriate ratings). The cathode connects to the 12V input of your door circuit.

Two redundant supplies, and if one fails, the other just continues to power.

Connect a lamp to each supply before the diode to monitor.

Or use the 12V before the diode to switch on a relay, with the contacts connected to a Sonoff or similar to monitor.

Or along similar lines, a 12V battery fed from a 12V charger through a Schottky diode. Monitor the charger before the diode with the relay. That way if you lose mains power you get an alert and the magnetic locks keep working off the battery for a while.

If you had two power supplies diode steered and the mains fails, you lose both supplies.

I think we are working to re-invent the UPS. :smiley:

A small UPS would indeed be another viable solution.

Everything is on a UPS, my problem what the the 12v PS failed to output 12v. It was still powered on, just not outputting DC voltage.

Then either the diode steered pair of power supplies or power supply/diode/battery will work for you.

You could use a mean well 12volt power supply with battery backup with charger built in
Iuse oneformy 12 volt needs in the house HA , solar assistant , 2 computers.
it supllies 9 amps at 13.8 and floats the battery till needed adjustable voltage

model drc 180 a

Please don’t necropost (this is a three year old topic) just to repeat what has essentially already been said. But if you must then at least proof read what you wrote before posting.