Fix this tiny White LED lamp near the door lock to locate the keyhole in darkness. It gives sufficient light to lock/unlock the door. It is a short duration timer which turns on the White LED by a press and after a 1 minute it automatically turns off.
You can make this Transistor timer easily for driving a relay for few seconds to few minutes. It is too simple and uses only two transistors and few other passive components. Just press on the switch to start relay and after the time ends, relay will switch off. You can also set the time using a Trimpot.
This simple transistorized timer can be used to remind an activity such as telephone use, heater on, pump on etc. It beeps at an interval of one minute to remind the activity. The circuit is too simple and can be assembled in 10 minutes.
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