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I need to add a time to flashlight or lantern so that it will switch itself off after maybe 20 seconds, what is the simplest way to do this please? Answered

I'd imagined it activating with a momentary switch, then maybe a dial /potentiometer to adjust the time, which would definatiely be less than a minute. I don't have any way to make up a pcb so please bear that in mind, thankyou

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Toga_Dan (author)2018-02-07

Capacitor discharge is an old-school timer. Not precise, but simple.

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iceng (author)2018-02-03

The MOSFET Gate gets charged and lights the LED until R2C_seconds discharge falls below 66%...
Pick the FET that works the current needed, (2N7000 - 100ma) or (BS170 - 500ma) and adjust the R1 value appropriately.

Click the pic to see the whole image !

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