Switching a GSM module off/on to save power.

Projects General Guidance
1

Hi,

This is related to a recent posting about power saving.

I have a battery powered project that includes a GSM module that needs to send an SMS about once an hour. The GSM module is quite power-hungry and requires high(ish) current regulator at 3.8 volts.

The GSM module is only needed for a few seconds every hour, but the voltage regulator I'm using (this one... http://uk.rs-online.com/web/p/low-dropout-voltage-regulators/6865869/) has a high background current of 40ma. So I'd like to be able to use the arduino to switch the regulator off most of the time and only switch it back on when it's required.

I'm kinda guessing that I can do this by controlling the input to the regulator with a thingy connected to a whotsit via a whatjmacallit.

Can anyone point me in the direction of a suitable circuit. Please speak slowly in your replies, electronics is all a bit vodoo to me. Existing regulator setup as shown.....

test1.gif

Thanks

2

Google 'HEXFET' or 'MOSFET switch'.

3

hmmm... having just looked at my own circuit again, I guess I should investigate what the enable pin does.

4

According to the datasheet, the regulator can be switched on and off using the enable pin. it says....

The SPX29301/02 have an Enable function that switches the regulator on and off. Their thresholds are TTL compatible.

Does this mean it can be connected directly to an arduino digital output pin?

5

Please remember to power the GSM module down with a software command, before you cut the power. Doing that will make the module properly detach from the mobile network.

6

Doing that will make the module properly detach from the mobile network.

Ok, but why? What happens if I don't? I have used GSM modules extensively in the past and have just pulled the plug without any shutdown routine.

Also, I assume there is an "AT" to detach from the network, do you know which one?

Thanks