My project consists of 3 piggy back boards.
First the Arduino UNO, then the Motor Shield on top, then a self-made circuit that incorporates a temperature/humidity sensor on top of that.
The sensor works if the pins of the self-made circuit is pushed directly into the headers on the UNO. It does not work when pushed into the headers of the Motor Shield, when all three are combined.
The voltage across the Vin - GND pins of sensor is correct, but output voltage is almost non-existent. Perhaps not getting enough current through the sensor? Placing a multimeter in series with the input the sensor suggests that this is the case.
Any ideas about what might be going wrong?