I'm an Arduino newbie. I registered in this web just a few months ago, I hope to contribute with something.
I'm working with an Arduino UNO, a GSM shield(SIM900 S2-1040S) and a motion sensor(HC-SR501). To power the shield I'm using the Arduino's 5V pin. When I use just the GSM shield (without the sensor motion) all works fine. The problem is when I add the sensor motion sharing the 5V pin (using a breadboard) with the SIM900. In this scenario, when I press the SIM900's button power, the GSM shield can't attach to the GSM network, seems energized but the LED that show you if the shield is connected or not, just stop blinking.
So, I think I'm doing something wrong. Will I be exceeding the power consumption limit? I don't think so. Until I know, the SIM900 consumes 1.5mA (sleep mode) and the sensor motion 60 uA. Maybe I'm missing something related to the breadboard or to basic electronics concepts. The connection scheme (currently in use) is as follows:
You can't power a GSM shield via USB, nor the Arduino 5V, they cannot provide enough current.
GSM devices may require peaks of several amps, depending on signal conditions - the reason
your setup sometimes worked and sometimes didn't is likely due to changing signal
strength, nothing to do with the motion sensor.
thank you MarkT for the reply. I connect the external power supply directly to the GSM shield and now works properly
Now the USB port feeds the Arduino board. What happen If I want use only one external power supply? It's possible feed the Arduino board via the GSM shield?
