The CR2032 is specified at 0.2mA continuous current (see http://www.houseofbatteries.com/documents/CPN-CR2032), so running LEDs off it is way over its design spec. It might just work though. You can buy these cells at many supermarkets.
dc42:
The CR2032 is specified at 0.2mA continuous current (see http://www.houseofbatteries.com/documents/CPN-CR2032), so running LEDs off it is way over its design spec. It might just work though. You can buy these cells at many supermarkets.
Either a coin battery or a small Lithium Ion battery.
Thanks for the help!
Best regards!
Edit: Alright if we take the leds away and just uses the button.
If a make a keypad on 4 buttons (1,2,3,4) which battery will work then? The pushed button will be saved in EEPROM storage.
I think I'd try the CR2032 first. Although it is intended for low-current applications, I've just connected one to a LED using a 220 ohm series resistor, and the LED lights up fine.
The lithium ion battery would also be a good bet, but you will need exactly the right charger for it.
Just bear in mind that any lithium-based battery can decide to self-destruct and get rather hot if it doesn't like what you are doing to it.