I'm a retired ME, shop experience with electrical/electronics. I want to add a simple (?) variable timer to a 7 LED display powered by 2 triple-A batteries so it can be on as a night light or whenever I wish it to be illuminated. Suggestions?

 

Welcome to AAC!

How variable of a timer? Minutes, hours? Accuracy?

LED color? Affects forward voltage which influences how LEDs can be wired.

Brightness?

Someone will be along shortly to recommend a PSOC4...

 

Welcome to AAC!

How variable of a timer? Minutes, hours? Accuracy?

LED color? Affects forward voltage which influences how LEDs can be wired.

Brightness?

Someone will be along shortly to recommend a PSOC4...

Didn't realize it was that critical. Oops.
1) Variable by quarter-hour to multiple hours (up to 12 on/off)
2) LEDs are white, all on same existing ckt.
3) Brightness is not measured but definitely above candle illumination; they light up as white.

 

1) Variable by quarter-hour to multiple hours (up to 12 on/off)

That eliminates a 555 timer. You're looking at a many bit timer (like CD4060 14 stage counter with oscillator).

How do you envision setting duration?

2) LEDs are white, all on same existing ckt.

Forward voltage is too high to be able to wire 2 in series, so more power wasted in current limiting resistors.

3) Brightness is not measured but definitely above candle illumination; they light up as white.

LED part number?