Pic Consumption

quicksilver · Joined: 04 Feb 2009 Posts: 31

Hey Guys, I'm working in a project in which I have to save as much energy as I can. So I've been thinking how to sleep the pic, and how to wake it up from sleep. So, I'd like to hear some suggestions. I know that I can wake up the pic with different sources like an external reset, using the WDT, or an interrupt. I've been thinking to use an external oscillator, or probably the WDT. I tried to use the Ultra low power wake up, and it works, but the frequency jumps from one value to another, it's not constant. So, I'd like to know which property works better, using an external oscillator or the WDT, and which consumes less current or energy.

Thank you very much.
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jgschmidt · Joined: 03 Dec 2008 Posts: 184 Location: Gresham, OR USA

Microchip has several documents on designing for low power. Check out their "Low Power" section from the main web page.
These APP Notes may help:

http://ww1.microchip.com/downloads/en/AppNotes/01416a.pdf - Low Power Design Guide

http://ww1.microchip.com/downloads/en/DeviceDoc/01146B_chapter%202.pdf - Low Power Tips and Tricks

Cheers, Jurgen

temtronic · Posted: Thu Mar 29, 2012 11:30 am

Use a bigger battery ! Really, unless you've got a government grant to do R&D testing for 'ultra low power products' you're wasting your time.25 years ago uchip had a great appnote about power vs modes, still valid today, but you have to consider the peripherals attached to the PIC,your actual code, external events,etc.
Back then I went from 24 4000series CMOS devices to 1 PIC but actual power consumption didn't really go down. Paying an extra $2 (lots back then) for a bigger battery was a LOT easier than spending thousands in time to optimize code, sourcing ultra low Vregs,etc.
Not saying it can't be done...but the ROI is lousy !

jgschmidt · Joined: 03 Dec 2008 Posts: 184 Location: Gresham, OR USA

Agreed, bigger batteries are cheaper in the long run. But for those who want small size, the challenge of running at low power, or to run off scavenged power - ambient light, heat, etc. there may not be an option. Here is another reference I found useful when I was working on a low-power project:

http://qwikandlow.com/ - Coin-Cell-Powered
Embedded Design by John Peatman. This is a free e-book.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Post your PIC and battery voltage, type and size. Also post a description
of what your project is about, and a description of the external circuits.

gpsmikey · Joined: 16 Nov 2010 Posts: 588 Location: Kirkland, WA