Interfacing GPS module with Arduino card

Projects General Guidance
1

Hello everybody, I don't know if I'm posting on the right forum, if not I'll delete this topic.

Firstly, my project was to connect 2 GPS modules on a Arduino Mega 2560 through the UARTs and also an IMU card in order to make data logging (on a SD card).
But my problem is that the GPS module needs to be powered by ~170 mA, and ~120 mA for the IMU card.
I've read the datasheet of the Arduino Mega 2560 and I saw that the max current is only 50 mA per pin so obviously it's not enough to power my GPS module.

I'd like to precise that I really can't use another less consumptive (does this word exist ? :p) GPS module.

Anyone of you have ever faced a problem like that and what could be the solution ? (I can work with others cards too, as long as they have 4 serial ports)

Thank you.

Regards

2

I saw that the max current is only 50 mA per pin so obviously it's not enough to power my GPS module.

It is 40mA and you do not power a GPS module from an output pin. You connect its power pin to the power pin on the arduino if it is 5V. If it is a 3V3 module then check if the 3V3 regulator on your model of Mega can cope. If not use a 3V3 regulator from the 5V pin to get your power. Remember to connect the grounds as well.

3

Grumpy_Mike:
you do not power a GPS module from an output pin

Maybe I'm misunderstanding the OP, but it seems to me that sometimes it makes sense to power a GPS (or any other device) via software control. Depending upon your requirements, doing something like that for a GPS could significantly reduce the power usage for a device.

And wouldn't you do that via an output pin?

I'd like to do the same thing for a board I'm working on. I only need GPS data once a minute (at best) and would rather keep power usage as low as possible. So as a generic solution, please take a look at the attached image. I exported this from a board I'm working on.

The GPS connected to JP2 is 5v tolerant and has the following pinout:

1- N/C (this is GPS RX)
2- GPS TX
3- Ground
4- VCC (2.8-5.5v)
5- VBAT 1.8-5.5v)

Assuming a fairly low power requirements (my GPS uses a peak of 50mA tracking in the default mode) is this a reasonable solution for myself as well as the OP?

Regards,

Brad.
KF7FER

EDIT: Cleanup and I did want to mention I plan on splitting off VBAT and powering it via a coin-cell to allow warm-starts for the GPS

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Trying to draw more then 40mA from an output pin will damage it. The figure of 40mA is the absolute maximum that it can supply before damage begins. The recommended maximum current draw is around 20mA. If you want to switch the GPS with the arduino, use a transistor.

5

consumptive (does this word exist ? :p)

Yes, it exists, but it usually used to refer to a tuberculosis sufferer, e.g. Mimi, the character in la Bohème was said to be consumptive or a consumptive.

6

And wouldn't you do that via an output pin?

Only through a transistor. Use a PNP to switch the high side.

I only need GPS data once a minute (at best) and would rather keep power usage as low as possible.

So how long does it take for a GPS to start giving position readings? If you turn it off then on you have to wait that long again.

is this a reasonable solution for myself as well as the OP?

No, you should not power switch it by low sided switching.

Talking of the OP

my project was to connect 2 GPS modules on a Arduino Mega 2560

Why two? They will give you the same position won't they? Or is it a very long wire that joins them?