I have a circuit that I'm using which generates the following waveform for a total of 5 seconds.
I need to use this waveform (which is essentially a bumpy 5 second pulse) to turn on a 12v DC power supply (from a car battery) for 12 hours. Yes, hours. I thought of using a 555 timer as a monostable multivibrator, but they are only good for up to 10 minutes. I need the 12 hour "on" state to be accurate down to +/- 1 second. Oh, and I need this to be as efficient as possible since it's a battery powered application.
For 12-hour delay, a digital scheme like millis() should be about 100,000X times
more accurate [rough guess!] than using any kind of analog device like 555,
which uses RC-charging.
Look for a "logi-level" MOSFET, meaning the gate can be driven with 5V; non
logic-level MOSFETs require 10V drive. Something like IRL540, the "L" indicates
logic-level.