What I would like to do is have an LED turn off 1 minute after the power is turned off. The LED would be on all the time when power is on. Thus:
Turn power on: LED comes on immediately.
Turn power off: LED stays on for 1 minute and then turns off.
This is to signal when someones eyes have adequately adjusted to the dark in a darkroom.
Thanks in advance.
Best Answer
You may want to consider just running the LED from a large capacitor - no extra power supply required.
Values would need to be experimented with (C1 in the region 1000uF - 10000uf) but you should be able to get about a minute and it has the advantage that the circuit automatically dims the led as time goes on - useful in a dark room situation