On Mon, 23 Jun 2008 18:16:31 +0100, "Tom=E1s =D3 h=C9ilidhe" said: > = > I'm using the PIC16F887 in a portable device that's going to run off = > batteries. > = > The device will have 7 LED's on at a time, so the total power = > consumption will be about 1.05 watts. > ( 5 volts * 30 milliamperes * 7 =3D 1 050 milliwatts) > = > In my previous design, my power source was one of those 9 V square = > batteries, which I fed into an LM7805 to give me 5 V, and I used this 5 = > V to power everything on the board (the uC, the logic chips, even the = > LED's). > = > This time around, I'd like advice on: > 1) What power source to use (e.g. a 9 V square battery) > 2) How to get 5 volts from the power source (e.g. an LM7805) > 3) Whether to power stuff like the LED's off the square battery or off = > the LM7805. > = > I'm kind of new to this stuff in a way so I'd appreciate if you'd spell = > things out instead of using abbreviations and initialisms. Also if you = > have the vaguest idea I won't know what you're talking about then please = > be extra elaborative! Do you require exactly 5 volts? In other words, are you using the A/D converters on the PIC and need to use the supply as a reference? If the answer is no(or maybe not, you can use an external reference or calculate based on the internal 0.6 volt bandgap reference), then just skip the regulator and run off three AA or AAA batteries. After all, the ampacity of a 9 volt is tiny and you are running LEDs! AA batteries will easily give you 5 times the run life. Cheerful regards, Bob -- = http://www.fastmail.fm - Does exactly what it says on the tin -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist