On Mon, 30 Jul 2007 16:59:51 +0100 Ian Stirling <[EMAIL PROTECTED]> wrote:
> Visti Andresen wrote: > > While I do find most of the GPS based ideas intriguing I do have one > > comment. > > > > Power usage! > > ============ > > > > I wonder if you have realised that the GPS consumes large quantities of > > current. > > (45 mW according to > > http://wiki.openmoko.org/wiki/Neo1973_Power_Management#Approximate_power_draw_of_various_subsystems) > > The 1200mAh battery will be drained in 1200mAh/(45mW/3.7V) = 98h ~= 4 days > > > > And this is for the GPS receiver alone and no power conversion losses, > > but GPS reception also requires CPU power.. > > > > This is not quite correct. > > The GPS can be turned off and on. > 45mW is for continuous positioning, 1s/45s will give completely fine > positions, though not as accurate as if it was on for longer. > > If the 'Resume in under 1s' from sleep entry on the table at the front > of the above page is done, then the numbers change again. > If it takes 350mW for 1s to wake the device, and then 80mW for another > second (CPU in slow mode and GPS on) that's 430mWs. > > One position per 45s, that's some 9mW average, or around 5% of the > battery per day. > It seems likely from the basic figures that this can be stretched to 1s > wake every 3 minutes or so, for around 1.5%/day. > After this, you need to wake up for more than a second to keep the > position current, so after 3 minutes, the next halving in battery use > might end up at 4 hours or so. > > This can also do bluetooth and WiFi polling of course (at a slight power > cost) But does a GPS not require large amounts of time to get a "new" fix? Hot startup 12s, average Warm startup 38s, average Cold startup 60s, average (random data from http://www.alibaba.com/catalog/11694061/Bluetooth_GPS_Receiver.html) I must admit I don't know when one needs to reacquire the fix... Of course even a 38s/60s power consumption reduction would be quite noticeable, even if one has to switch to continues operation when moving (in order to notify me that I have to pickup groceries) > > _______________________________________________ > OpenMoko community mailing list > community@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/community _______________________________________________ OpenMoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community