I wanted either red or white LED's flashing from a 2 or 3 volt source. White LED's would require some boosting while red LED's would run quite happily down below 2V.
I put this together at lunch time to prove the idea and adjust flash rates...
The 74HC14 is spec'd down to 2V, I ran the thing from about 2.5V. The LED I used was a random white LED. With the components shown the flash rate was a few tens of ms on and a few seconds off. C2 is used to boost the voltage across the LED.
That works ok, now I need to switch it on/off depending on ambient light....
Swapping the 74HC14 for 74HC132 makes this a bit easier.
