Final version of my NE555 timer door control (circuit # 4503779493543936). Switching the solenoids is now done by MOSFETs (IRFZ24N or IRLZ24N). The rest of the circuit hasn’t changed much at all.
Solenoids are 6VDC types with a 100% duty cycle operated in overdrive on 12VDC for increased power from smaller and cheaper solenoids. For the short actuation times this is not a problem at all and also lies well within with the manufacturer’s maximum ratings.
Edit: Added LEDs for better visualization and forgotten diode at second timer; the simulation doesn’t require it but IRL it’s necessary. There was also a weird glitch with the MOSFET for the second solenoid opening for milliseconds on power-up of the second timer. It doesn’t happen with the LED and resistor in parallel to the solenoid, a regular diode and 10k resistor will also suppress the transient. I think it’s a simulation issue; I have used the second timer design in the past for other purposes, like turning on speaker outputs with a delay, and have never seen this glitch IRL.
Simulation runs at half speed.
