ted:
When pin EN is connected to 0V regulator is off = sleep, when is 5V regultor is on
Brilliant! I'd have to play with it to see how it works. Looks like only 4 pins, Input, Reset, Enable, and Output, and ground.
Looks like the current consumption is ~20uA....not bad.
Wawa:
The mosfet that switches the LED uses no gate current from the 555.
An NPN transistor there would need ~30mA base current from the 555 for the ~300mA LED current it has to switch.
The mosfet power switch draws no gate current from the RC time circuit, so that capacitor can be small.
A normal transistor would influence that RC circuit too much.If you decide to use a Cmos 555, then you can try the RC circuit on the reset pin to enable/disable the 555.
You would then only need a mosfet for the LED (if you can live with the ~60uA idle draw of the 555).
Leo..
Ah I see, thanks. MOSFETS are a beautiful invention.
I'll check with my power consumption calculations to see how the 60uA draw would effect the battery life.