Hello, I'm designing a matchbox-termometer. It will consist of a 7-segment indication, PIC16F88 (18 pin) and TC77 - SPI temperature sensor (smd). The hard part is to find some sort of a power supply (battery) that will fit into the matchbox. I need 3-5V and about 100mA to drive the LED indication. I tried with 3 AG6 batteries (coin and button type) but it barely outputs 20-30mA. The whole device is powered only during the temperature reading and displaying - about 10-15 secs, so it won't be draining battery power in idle state. Currently I'm using a 9V battery + 7805, but that combination is bigger than the board itself :)
Can you come with some cunning sort of power supply?
Now I'm wondering if I make the LED indication blinking about 100 times per second (dynamic indication) with duty cycle of 0.5 (half time ON, half time OFF) will the power consumption shring in half? If I can make the 7segment indication draw 50mA that is more suitable, becouse I will put bigger resistors (like 400 ohms instead of 200 ohms) and the consumation will shring further into the capabilities of the 3 AG6 batteries...