Fail-safe latch for power-loss-to-delayed-release circuit

[frnx79_sj]

Hey all, need a reliable, cost-effective solution for a fail-safe latch on a secure enclosure door.

The idea is that the magnetic latch must hold while AC power is on. When utility power is lost, the latch must release automatically after a 10-second delay. This delay prevents nuisance cycling from brief power blips.

I'm wiring a normally-closed magnetic lock. Is a standard "delay-off" timer relay the best and most robust way to implement the power-loss-to-delayed-release control on a high-voltage circuit? Looking for a common industrial or access control solution, not an expensive PLC.

Thanks!

 

[whtRuss14n]

hi @frnx79_sj, for maximum simplicity, you can look for an Integrated Delayed Egress Mag Lock unit.
Companies like SDC, RCI, or Securitron make locks where the delay circuitry, horn, and reset button are all built into the mag lock housing or its dedicated power supply. It handles the 10 second delay on power loss automatically and is usually prewired for fire alarm tie ins. It's an all in one solution if you're looking for something that is certified and foolproof

 

[PGB1]

Detex makes many listed devices. Assa Aboly has some with end cap protection. If someone pries the end cap off, the alarm will sound.

 

[Alan]

A good delay-off relay is exactly what you want. It is simple and far less dramatic than a PLC overkill solution.