Having run out of digital pins, I wanted to monitor a switch that has 13.3V in the off state (0V when on).
I did the maths and installed a 5K6 and 3K3 resistor chain, expecting 4.9V on the input.
However, the UNO seems to be loading the circuit, so the pin voltage is dramatically reduced
and the analog read command only gives a value of 76 and not the 1003 I expected.
This is not a problem in this project as I only need an On/Off state, but my next project needs
an accurate reading from an LDR (light sensor).
I do issue the command:
It compiles Ok, but the manual is a bit vague in this area.
So, my question is:
Is there a built in load on these pins, or have I managed to damage my device somehow?