I would like to detect when the postman put mail in my box, so I was thinking about a simple attiny with tilt sensor (which would wake up the attiny) and a 433 MHz emitter:
The problem is that one cell coin (3V) is really low for this kind of emitter, it is good with at least 5V. So if I use two cell coins I have 6V and above max attiny voltage. If I plug it with one cell and emitter with two cells, the data pin will be only of 3V which is not good.
If I plug all on 6v, I have to use a zener diode or a classic diode to get below 5.5v but this diode will drain my battery even when the attiny is sleeping. How could I get a good voltage for the emitter without draining my battery?