- Joined Nov 10, 2018
As I have been helped a lot from other members' answers as a courtesy I want to give something back. I am relatively new to the hobby, maybe someone at the same level will find it (or parts from it) useful. We have a door that we keep forgetting to lock. Not anymore, this design will flash LEDS and after sometime will sound a buzzer. This is finished now and works fine, this doesn't mean the circuit is optimal. The switch on the right will stay pressed as long as the door is unlocked. The 555 timers will flash the red & yellow LEDs alternatively with the green one and after a while the buzzer will sound. How much time after depends on the trimmer pot position, somewhere between 30' to 3 mins. When door is locked the green LED is on all the time. Actually I did not plan initially the green LED to be permanently on but it happened accidentally and I liked it as it gives a high tech tone to the house. There are times that the door needs to be unlocked for some time when going constantly in and out doing errands for example, so the DPDT switch comes in to play. When it is on the other position the LEDs flash continuously either the door is locked or not, but with no sound. The LEDs will remind to put the switch back when finishing the errands. I posted recently parts of the circuit asking questions. I know now that some parts like that PNP transistor are not necessary, but it is too late now. You may find other parts that are not needed... But I insist on that MPS A13 transistor, as the area in the lock is confined a I had to make a DIY switch with a spring and a small piece of metal, so the conductivity is questionable. Please ask if something is not clear.
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