Need an auto-off timer switch for my home-made electronic lock
It consists of a couple of solenoids, a remote controlled pass-through plug socket and a shaver adapter (lol)
The RF remote turns the plug socket on and the plugged-in shaver adapter carries current to the solenoids which causes them to retract so I can open the doors.
I can also use the remote to turn-off the plug socket (thus releasing the solenoids, locking the door if the door is shut) But the problem is that sometimes I forget to turn the system off and the (still-retracted) solenoids get hot after 20-30 minutes, which is an obvious fire hazard.
So I'm looking for a timer that will shut-off the system after a few minutes. I've seen plugs on eBay that are designed for hair straighteners and turn connected devices off after a set time, but they all operate at 30mins+ and most require you to push a button to set the countdown timer, which is just completely useless for me. I want a timer that starts as soon as it's powered-up and shuts down the solenoids after a couple of minutes if I forget to shut them down with the remote.
Any ideas where I could get such a thing? They're operating (via the shaver adapter) at 4.2VDC if that helps
I've included a photo of the RC plug and shaver adapter in case I didn't explain it very well