Key timer release

I’ve assembled this device and it functions effectively, Electromagnetic key release. Components- Relay for driving lights sourced from an auto parts shop. 240 or 110v timer 12v transformer, needs to output DC power; examples include battery drill chargers etc. The Key must be steel; verify with a magnet. How-to Pry off the relay cover and remove the contact bar. Connect the 12v from the transformer to the relay coil contacts. Plug the transformer into the timer, then plug the timer into a power outlet. Set the timer start now feature to your desired time. The moment the coil energizes, place the key on it and suspend the assembly where convenient. At the end of the set time, the timer cuts off the magnet and the Key drops. Even if there is a power failure, the Key will still drop. Having a precise release timing can be beneficial. Ice backup remains advisable though. Apologies if this has been shared before. Photos