Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Commanderbob on July 08, 2008, 10:15:43 AM

Title: GPS sleep/low power?
Post by: Commanderbob on July 08, 2008, 10:15:43 AM

I am using a GPS in a hand held device and I need it to go into power off/sleep, but the GPS does not have a mode like that. I was thinking of using a MOSFET on the power line so I could turn it on and off. Is there any better ways  to do this or is that a good idea?
Thanks,
Justin

Title: Re: GPS sleep/low power?
Post by: airman00 on July 08, 2008, 10:37:11 AM

you wanna turn it off? or turn off the screen and stuff like that to save power? or turn off everything besides the micorocontroller?

Title: Re: GPS sleep/low power?
Post by: Commanderbob on July 08, 2008, 10:50:02 AM

I am using this (http://www.sparkfun.com/commerce/product_info.php?products_id=8621) GPS. The AVR, OLED, and FRAM can go to sleep but the GPS can't and with a whopping 45mA of current draw it can's be left on or the battery will drain too fast when the device is "off". I need a way to cut its power when the system is off or it is not needed.
Justin

Title: Re: GPS sleep/low power?
Post by: airman00 on July 08, 2008, 11:44:57 AM

why do you need sleep mode , why not just turn the damn thing off ,  :)

use the mosfet idea you had  , or maybe use a relay

Title: Re: GPS sleep/low power?
Post by: dunk on July 08, 2008, 03:15:42 PM

you sure it hasn't got a low power mode?
the sparkfun page specifies a "Warm start" time of 38 seconds implying it is possible to suspend the module.

dunk.

Title: Re: GPS sleep/low power?
Post by: Commanderbob on July 08, 2008, 08:43:32 PM

I asked the manufacture and they said it did not. A warm start does not mean it is suspended.

Quote from: http://gpsinformation.net/main/warmcold.htm

    Search the sky    -   Time, position, almanac, and ephemeris data all unknown.
    AutoLocate    -        Time, position, and ephemeris unknown, almanac known or partially known.
    Cold Start    -           Time and position known to within some limits, almanac known,  ephemeris unknown
    Warm start      -       Time and position known to within some limits, almanac known, at least 3 SVs Ephemeris are known from previous operation.

Quote from: airman00 on July 08, 2008, 11:44:57 AM

why do you need sleep mode , why not just turn the damn thing off ,  :)

use the mosfet idea you had  , or maybe use a relay

That is what I want to do  :). I just wanted to know if there were any better ways to turn it off with the AVR other then with a transistor/relay. I have to be able to keep it off when the AVR is in "power-down" mode. Does anyone know if the IO pins keep the same state or do they go back to high impedance?

Thanks,
Justin