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?
Didn't realize it was that critical. Oops.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...
That eliminates a 555 timer. You're looking at a many bit timer (like CD4060 14 stage counter with oscillator).1) Variable by quarter-hour to multiple hours (up to 12 on/off)
Forward voltage is too high to be able to wire 2 in series, so more power wasted in current limiting resistors.2) LEDs are white, all on same existing ckt.
LED part number?3) Brightness is not measured but definitely above candle illumination; they light up as white.