pic microcontroller discussion list <> wrote on Friday, June 20, 2003 8:24 PM: > Hi all, > > Got my timer/clock working and tuned down for low power, but from > various archive posts, I feel like I should be able to go lower. In > a nutshell, think of it as a digital clock w/3 switches, 4 LED digits > and a buzzer. Normal operation is internal clock at 4Mhz, AND > external osc (Timer 1) at > 32.768kHz. There are 2 modes -- normal and sleep. > > In normal operation, I get ~52mA. No prob. > > In sleep mode, the internal osc is shut down and all LED's are off, > and only Timer 1 wakes up every 1/2 second (which wakes up the > internal osc), runs about 50 instructions and goes to sleep. During > all this time, RA4 (open drain) is such that it draws no power during > the brief wake up. In this mode, I get 0.12mA average. > > Is lower possible? Or am I asking too much? I don't *need* it to be > less, but would be nice to know/learn if any other optimizations are > possible. Is the A/D off? Is the voltage reference off? Is the WDT off? Check each pin with a resistive pull to each rail, if the pin value changes, it isn't set as an output! If it's a '628 with dual speed clock, you could set it to 37kHz for lower power when on, obviously it would be on for longer though- has anyone measured the relative power drain in this sort of application? I guess it isn't a simple calculation because of oscillator startup time etc. One other thing, how are you measuring the current? Could it be the meter at fault? You could try a largish resistor in series with the power and measure voltage across that- aim to drop, say, 100mV across the resistor. Nigel -- Nigel Orr, Design Engineer nigel@axoninstruments.co.uk Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT Tel:+44 1467 622332 Fax:+44 1467 625235 http://www.axoninstruments.co.uk -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.