Writing code for battery operated projects

[Melanie]

Hi Jessey

1. Turn OFF all unused Hardware in your PIC befor going to SLEEP... ie... switch-OFF the ADC, PWM etc. That includes switching-OFF your weak pull-up's too.

2. Is this a NIGHT/DAY Sensor type application or a Room Occupancy Sensor kind of application? If it's NIGHT/DAY, then it doesn't get light instantaneously... so why not go to SLEEP for longer periods of time - like ten Seconds or so.

3. If you use Comparators (eg 877A) rather than an ADC, you can have your PIC woken from SLEEP when the light level exceeds a pre-set value.

4. There are better PICs than the 877 for Low-Power use... Microchip has a whole bunch of micropower devices that only consume a few uA when running - let alone when asleep. Also, that's a BIG PIC (in more ways than one!)... so I'm questioning whether you need all those pins for a simple Battery powered application. The 12F683 for example has Comparators, ADC and PWM and will consume far less power than that old 877 (quite apart from the fact that the 877 is probably bigger than your average car Battery!!!). Actually, I've got 877's gathering dust in a drawer here for over two years because it's just not worth designing products with that device.

[mister_e]

in addition to Melanie, turn off all power that goes to your external device..pot and blah blah. Also, use voltage regulator with the lowest quiescent current need. Regular 7805 are not appropriate. 78L05 are better but there's a bunch of more efficient.

12F683 is a good choice if you need PWM and ADC. The POT command is not appropriate to read from a POT when your PIC have internal ADC. Should use ADCIN instead. 12f675 will also do the job if your skip the PWM to a home-made sound procedure.