Hi, Malc

Do you understand the "why" of the Parallax document, now ... ???

You'll have to place your Button Key INSIDE the vivarium ( hé,hé ... WITH the snakes !!! ) if you want a true image of your temp.

The graphs you've shown can't be used to finely trim a regulator ... but are a good example.

Temp measurement and moreover probes placing is a real art ... to get a nice temp regulation.

But let's begin by the beginning :

ALL you have to do already is in ZE Book ... with relevant code.

We'll see details later ...

Till then, I'll implement the PID Regulator on my existing " 84 " Thermostat ( not the one shown here, but a nicer one which is pin for pin compatible !! )

Alain