brainwagon

Lee mentioned that the there was a way to change the analog reference used on the analog inputs to the Atmel AVR to an internally generated 1.1V, which would give me a lot greater resolution (about little over 1mV per step). Indeed, a little quick searching yielded that it was not only true, but dead simple: the Arduino provides an “analogReference” call. If you simply call it in your setup() routine with the argument INTERNAL, you’ll get a 1.1V reference.

To test it out, I did another run, pretty much the same as before, but illustrating the values read after changing to the internal 1.1V reference. Again, I began with the diode in air, then pinched it, released it, pinched it, then released it, then placed it next to a cold can of Diet Coke I had sitting next to me.

Seemed to work pretty well!

Kragen mentioned that the Atmel also had in internal temperature sensor as well. Indeed, it appears that you can simply do an analogRead(8) to access an internal “virtual pin” that links to an internal temperature sensing node. (On the Arduino Mega boards, the pin will be a different one) Read about it more here. I’m currently just using an old ATMega168 which doesn’t seem to have that capability, so I haven’t tested it. It appears that the sensor is noisy and uncalibrated, but it might be useful in some applications. When I dust off one of my more recent boards, I’ll give it a try.

Okay, time for breakfast.