Analog reading problem with Ethernet shield connected

Other Hardware Sensors
1

Hi,

I seem to have a problem with analog reading, from e.g. a LM35 (or a 10turn pot-meter for simulation), with an Ethernet shield stacked.

The LM35 is connected to A2 and the Arduino UNO is supplied with a seperate PSU (9V-900mA).

Without the Ethernet shield attached, the reading is working perfect, but with the shield attached the reading is in saturation ~ 1023.

I have tried finding a solution in the forum, but so far without any success.

Could someone be helpful to give a comment - thanks in advance!

2

Make sure the Ethernet shield is not using the pin A2.
Also check that the Ethernet shield is not causing a short to ground on the Aref pin. Use a meter to check the voltage on this pin.

3

Hi Grumpy_Mike

Thanks for your reply. There was a short on the AREF.

Is that a commonly know issue or do I miss do some initialization somewhere?

4

I have come across one person who had the same fault, the spacing might be close. Was it a mechanical short, that is something touching that should not?

5

I actually just removed (bend the leg...) the connection on the Aref, between the UNO and the Ethernet shield and that solved the problem.

When I get the time, I will try to analyze further - but it seem to be a short on the Ethernet shield.

Thanks for your comments - most helpful!