Re: Arduino + MCP9600 + thermocouple help needed

"Richard Smith"  wrote in message news:m1ttl3qahq.fsf@void.com...
"Second picture is where commented-out "pinMode(2, INPUT_PULLUP);". Initially LED lighting randomly when button not pressed. Then added in the circuit the "pull-up" resistor connected to on-board supply voltage and the circuit behaved like the first circuit."
Unconnected inputs are sensitive antennas that pick up secret messages from space, or noise from fluorescent lights and radio/TV transmitters. Some even float to a middle level where they partly turn on both the input high and input low circuits, causing oscillation or higher power consumption. They are all best made high or low if not used. When you have an oscilloscope touch the probe to your finger and see how much electric noise you carry around.
The traditional initiation rite into electronics is releasing the magic smoke. Hopefully it's one-time, like forgetting to lower your helmet
https://www.ntnoa.org/LucasSmoke.htm