another GPS idea - speed-sensitive voicemail (Power usage)

Visti Andresen talpa at galnet.dk
Mon Jul 30 17:45:12 CEST 2007


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..

If the CPU @ slow mode is 50mW and the GSM at idle is 30mW,
then I would consider 45mW quite an addition power drain.

It of course gets even worse if the GSM can wake the CPU from SYS_POWER_SLEEP
http://wiki.openmoko.org/wiki/Neo1973_Power_Management#SYS_POWER_SLEEP
Hence only the GSM has to be active? (plus some minor power drain for the 
CPU)

That said I might actually still opt to have my standby time cut to 
33-50%




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