堆叠式屏蔽没有足够的电源-暗淡的PWR灯

Question

I'm stacking a SeeedStudio Bluetooth Shield on top of a Olimex EKG/EMG Shield .

At first, I stacked the two loading only bluetooth shield demo code and all the LEDs lit up brightly and worked fine.

Now (having only taken a shield off and put it back on), the lower shield's (Olimex) power LED appears dim and the upper shield (Bluetooth) is not powered at all. The lower shield's power LED brightens when I remove the top shield.

Not sure what happened here -- both shields work perfectly if they are the ONLY shield on top of the Arduino. Is there any way for me to check the output voltage coming from the lower shield (Olimex) to the higher shield (Bluetooth) with a multimeter to see if it's sufficient (3.3V)?

Answer 1

Looks like you may really have a current problem. Your Bluetooth shield can draw up to 100 mA and it is 3.3 V. Your Olimex shield does not have details about the power but even assuming 20 to 30 mA, looks like you do not have enough current from the Arduino 3.3 V which is limited to 50 mA. The easiest solution would be to use an Arduino bluetooth shield instead of the actual one, which would be 5V instead of 3.3 V and then you solve the problem of the current limitation for both the Olimex and the bluetooth connecting the Olimex jumper to the 5V and the bluetooth on top. Alternatively, you can try to use a level shifter for the bluetooth on top of the Olimex. Slightly more complex but would allow you to use the 5V and save the actual bluetooth.