Button and coin cell batteries come in a few basic types. Lithium cells last a along time, have a high capacity, but they can't source much current. You shouldn't plan on drawing more than 100uA from a coin cell if you want to get anywhere near its rated capacity. You can light an LED from it, but it drains fairly quickly. 3V nominal voltage. The LR44 and simalr LR and SR cells are just tiny battery cells like your AAA or AA batteries. LR has more power (Alkaline, I believe) than SR. Your cheap digital calipers come with cheap LR cells and still don't last very long. They can supply up to 3mA and still provide their nominal capacity. They have a lower capacity than an equivilant size lithium. Nominal voltage of 1.5V. You may be able to ignore the dropping resistor on the LED and let the battery limit current. Rechargable cells are typically much lower capacity than primary cells, and have a higher self discharge. Still, a tiny lithium polymer battery is very small and stores a respectable amount of energy. These are ideal for high current usage (on the order of amps, rather than mA or uA). Nominal voltage of 3.7V Which you should use in this particular project depends on how much current the uC and sensor need for normal operation, how much current the LED needs when it's on, how long you need to ti run in normal operation, how long you need it to run while the lamp is lit, and duty cycle of the lamp (few seconds once a day, etc). Go check out panasonic.com, duracell.com, and energizer.com. Look at all the cell types in all the form factors and check out their rated discharge, capacity, and nominal voltage. Comparing the discharge curves of different chemistries is very enlightening - some are flat at their nominal voltage until they run out, some have a drop, plateau, then a slow drop, etc. Good luck! -Adam On 11/9/05, Jamie Jensen wrote: > I've been tasked with looking at using a 10F part to make into a 'smart' switch. This is a take off from the vibration sensor.....more like....if we did this different then we could do this... > > OK...make a long story short. Looking at the 10F series, switch input, driving an LED that will stay on for a few seconds when the switch is turned on. All very small self contained, almost throw away. So I can run this down to 2V and for a regular LED that wants 1.2V that will work fine. > > Battery. Whats a good choice...needs to be SMALL, inexpensive and maybe even solder tabs. Any pointers? I know, the bigger the cell, the longer it will last, so its all a tradeoff really. > > thanks a bunch guys > > -JJ > > > --------------------------------- > Yahoo! FareChase - Search multiple travel sites in one click. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist