Power supply for project with two boards

Projects General Guidance
1

Hi all,

i'm working on a project with an Arduino Mega 2560 and a Sim 900 gsm shield.
What kind of power source do i need to power both devices?
Arduino needs 12v 2a, the GSM shield also needs 12v 2a, but i dont want to use 2 adapters for this.

Any pointers to a power supply that i can use for this project?

Thanks

2

Really? When I looked at the specs, both need 5 volts. A simple phone charger should work for both.

3

Hi Paul,
Thanks for your input, you mean just one phone charger for both boards or a charger per board?

4

One phone charger. Check to documentation for each board and add the current requirements. Add 10% and that will be the current needed. Match that to the phone charger rating and the charger can be any current value that is the same or greater.

5

Thank you, i will try this tomorrow

6

Most phone chargers give out 500mA or 2A at 5V, both are more than enough for a 200mA peak mega and then some.

7

Now you have an initial answer, but the bigger question is, what will be added to the two devices that you haven't told us about? Will the Mega be loaded with LEDs, or a motor or two, or what else? These will all need to be folded into your power sum, before you buy or borrow a charger.

8

Not knowing what you have connected I will assume your current measurements are correct therefore I would simply add the 2A + 2A and come up with a single 4A supply.

9

The hardware in this project is 1 Arduino Mega, 1 GSM900 shield, 1 Barcode reader GM73 that will use 5V/90mA for operation. I cannot think of any other hardware i currently need.

10

Then you have your power analysis correct, though it's a waste of a Mega, surely. Regardless, carry on. A Schematic showing your setup might reveal assumptions about how you wire your power, but since you're facing no malfunction yet, it's not really necessary.

11

Why do you think this is a waste of a mega? can you suggest another board that is more suitable?

12

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Shows me what I need to know, you have two IO pins for talking to the Sim 900, obviously TX and RX for a software serial implementation in this case.
The Mega gives you 4 hardware serial, granted, so you have better comms than using ss, but you say nothing about what you're doing with the other 50+ I/O of the mega, so we're quite justified in thinking they're not being used, ergo wasted. There are other Arduinos with more than one hardware serial that don't have a huge footprint. In that way, I consider it a waste, but YMMV, of course!

1 Like
13

the Sim900 drops out when there is not enough power (powerspike 12v 2a?), i read that somewhere on the interwebs and it seems to behave that way. In your schematic you link the power to the sim900 but not to the arduino, doesn't it need power or is it powered through the sim900?
The arduino mega was the board i had around so i used it, but if this goes to production i will probably need a cheaper board but really want hardware serial because i think that is more reliable?

14

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