Sketch works with SM5100b cell shield in place on USB but not on external power

Using Arduino Networking, Protocols, and Devices
1

Hello,

I have a Arduino Uno, (AdaFruit) Screwshield and SM5100b cellular shield stacked together. The specifications for the SM5100b dicate that 5vdc at >= 2amp power be applied to the 5v and gnd connection rather then going through the Uno's barrel jack (which is limited to 1amp). Apparently, the cellular shield can draw as much as 2amp when transmitting.

My problem is that, my sketch will run when plugged into USB and the 5vdc external power source left disconnected. But when I disconnect the USB and plug it into my power brick... nothing. The SM5100b power indicator lights up... even my LED connected to pin 12 lights up (as the sketch tells it to) but I fail to get any SMS signals sent from the box.

I have tried two different power supplies (one 5vdc 2amp from AdaFruit and another 5vdc 4amp from MPJA). I even went so far as to try the sketch on a Arduino Pro with a (SparkFun) ScrewShield and a new SM5100b cellular shield. Still nothing.

Out of curiosity I uploaded the simple "blink" sketch to the Arduino Pro setup and the sketch will run with the ScrewShield in place... but once I plug the SM5100b on top... the sketch fails to start.

Unfortunately, since the sketches run fine on USB power ... I am somewhat limited in my ability to diagnose the SM5100b directly (serial communication would be done through USB and in turn get power).

Any thoughts?

Thanks.

  • Ben
2

The Uno requires a minimum of 6vdc on the power jack, and prefers 7-9vdc. 5vdc there won't do well.

Just a thought...

3

You tell us it runs fine when connected to the USB? It then consumes 0.5A max as the USB power is fused to that limit. Put a 7.5V wall adapter to your arduino and it will run fine I guess.
If you wanna be on the save side and have the power ready when the shield maybe sometime use it, an option would be to use an Iteaduino V2.1 instead of the UNO. It's DC/DC regulator is able to give you up to 3A at 5V and doesn't get as hot when higher voltages (e.g. 12V) are applied.

4

Hello

I'm getting problems ~ similar to yours.
Please take a look

Thanks on advance
Pedro Ferrer