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Need an auto-off timer switch for my home-made electronic lock Answered

Hello. I made my own (extremely basic) remote-controlled door lock a few weeks back.

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




5 years ago

No photo is attached to this thread. What is your setup and what components are you using?

Look into using a 555 timer circuit so that the signal from your receiver activates the 555 timer which will only activate the solenoid for the pre defined time you want. Do a search for a 555 timer calc which will help you find the parts needed to get the 555 timer to activate for the number of second/minutes you want.