I'm currently working on a small circuit, which I intend on running off a CR2032. The intent is to have the circuit last at least 2 weeks (the longer the better), pulsing a green LED every 3 seconds, with a DIP switch to toggle power. I'm planning to use a 555 timer with a generic green diffused LED, but I feel like there's an IC that may accomplish this more efficiently. What's the most energy efficient, small (the PCB is going to have a surface area no larger than 1"), simplest way to pull off this circuit with a CR2032 or comparable? Thanks guys!
Answer
The most efficient LED flasher by far was the National Semiconductor LM3909. This chip is no longer manufactured, but you can still buy it online.
It can flash an LED for years based on a 1.5-V "D" cell. One key to its high efficiency is that it uses the charge accumulated in the timing capacitor to help light the LED, rather than just dumping it to ground and wasting it.
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