SIM900 doesn’t connect to the network

Official Hardware Retired GSM Shield
1

Hi,

I bought my SIM900 module just about a week ago in order to send SMS messages, though it somehow doesn’t work. First of all, I put my 4G SIM card (it’s unlocked) into it and it starts blinking for a while and then
both tiny red LED turns off. As a consequence, it doesn’t even connect to the network. By the way, I power my module with 5 external batteries.
Unfortunately, I don’t know what might be the source of the problem.
I would be grateful if you could help me.
I thank in advance for your help.

2

can you clarify which batteries (can they provide 2Amps ?) and how the whole thing is wired (joined grounds with Arduino?)

3

Well, just like I mentioned I use the external battery case(sorry it has 6 battery at the same time ) which I got with the starter kit. Additionally, it is wired with the Arduino to be grounded.

4

that's a battery

image
image2564×1532 337 KB

I hope you don't have 6 like this in series...

so question again:

  • what type of batteries?
  • are they in series or parallel?
  • can it provide 2 Amps?
  • how does the whole circuit look like?
5

image
image1920×1440 367 KB

That’s all I have now.

6

I don't see any junction between the GND of the Arduino and the GND of your board. it will be needed.

So you have AA batteries.
Those are 1.2-1.5 V batteries but could go above 1.6V and you have 6 of them, likely in Series.

➜ have you measured the voltage you get from this?

The operating voltage of SIM900 chip is from 3.4V to 4.4V. The best shields in the market come with a high current, high accuracy, low-dropout voltage regulator MIC29302WU (To keep supply voltage safe at 4.1V) and the jack can be used with any good 5V-9V DC wall adapter.

➜ ensure you don't go over and hope you have such a regulator

On some modules, next to the DC jack you have a slide Switch to select the power source make sure you selected "extern"

You also have usually jumpers so that you select where the (RX,TX) of the shield connects to: either Software Serial(D8,D7) or Hardware Serial(D1,D0) of the Arduino when used as a shield

7

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