Basic PID Controller (Independent Form)

There's a good reason to place the derivative on the measured variable rather than the error. It turns out it's a mirror image so must be subtracted, rather than added, from the total. Look up derivative kick if anyone interested. I'm not sure how big a deal it is in this simulation but it's certainly a big deal in real life so maybe get used to it.
I've kept the form as simple as possible here to make it easier to understand (hopefully).

Auto destruct

really?

@pedro16797 All good points Pedro, I'll put out a V1.1 later, bit busy right now, unless you want to do that...

An improvement in the condition for setting the integral to 0 could be
Err*pErr<0

I would place the set variable prev Err after the wait dt or else you're using the uninitialised err in the first iteration