SIM900, net problem


I recently bought this shield from sainsmart :

And I connected it to my Arduino UNO.
I really lack documentation and I decided to use the RX/TX pins connected on 0 and 1
I used a very simple code (with a french cellphone and having disabled the PIN code):

#include <SerialGSM.h>
#include <SoftwareSerial.h>
SerialGSM cell(0,1);
void setup(){  
  cell.Message("ça marche ma caille?");

void loop(){
  if (cell.ReceiveSMS()){


Here is my problem :

When I switch on the SIM900 power button on the shield, the status Led remains lighted (ok) and the NET Led blinks (5 x 800ms) and is switched off. Then, the shield is inactive again. The strange thing is that when I remove the sim card from the shield, the NET led continues to flash permanently.

That means I can’t use the shield because it isn’t active as sort to find an available network. I made several researches. Some people say that these kind of shield should need an external alimentation. However, there isn’t a plug on it for the alimentation. I’m wondering if the problem is really related to the alimentation.

I asked Sainsmart support additionnal informations about this shield but without success.

Many thanks for your advices.

Ok, I found a power supply : 15V 800ma

This works now, that means this was only a question of power! Why sainsmart do not provide a clear reference?

Badiou: Why sainsmart do not provide a clear reference?

Indeed, but they do tell you that it consumes 1.5 mA in sleep mode.

Most SIM900 shields have their own power jack and require 5v 2A, not that they are more inclined to tell you about this than Sainsmart. I imagine you can run the rest of the boards from this.