# required current

Hi!

I'm studying the feasibility for a project with an arduino board linked with an arduino gsm shield.

I don't find anywhere the required current of them. I need to know how many ampere they absorb when they are in standby status. I have a battery of 12V - 7,2Ah.

Someone can help me?

Thanks

bob87lc

It really all depends on what you do with them.
It'll be hard to calculate the current on a reliable bases, you really need to measure it.

The GSM shield could spike a current when it's sending, but because it's current is drawn from the arduino, it can't be more that 500mA@5V and 50mA@3.3V.

So in the worst possible scenario, a fully charged 7.2Ah battery can last around 13 hours, but I highly doubt it'll even gets close to it. My guess is that it'll last for over 24 hours.

The application will send sms once in a while, just in case of allarm (once per month for example). And in other situation the arduino will stay in standby.

Will it absorbs always 500 mA?

And why 500 mA@5V and 50 mA @ 3,3V? Not the contrary?

Thanks

Oh wait, the 5V can supply a maximum of 1A.... oeps

But no, it won't draw 500mA constantly, hence me saying "worst possible scenario".

And the electronics used on the board to create the 5V can maximally supply 1A (Not 500mA, sorry for that) and the one for 3.3V can supply a maximum of 50mA.

It seems you want power your project with a 12volt SLA battery.
If so, choosing the right hardware is crucial.

You don’t want Arduino’s lineair regulator to overheat when more than ~200mA is drawn from the 5volt line.
So adding switching supplies is a must. That will also double your runtime.

Will there be any charging, like solar cells.

Post links to the hardware you think is needed.
Leo…