Homebrew PCBs

> Tony,
> You wrote, "I figure I can do it by monitoring the heater, and when it
> switches off for the first time use that to start the timer."
> 
> No, that won't work.
> 
>   Any decent PID controller properly set up will start to cycle as it
> approaches the setpoint temperature. That cycling point is controlled


Yeah, I wasn't optimistic, I figured I might be pretty close to the target
temperature when the first cycle happened.  If it happens minutes out
that'll be a problem.  The timers I have only need a single pulse to start
(ie the heater changing state), so I guess I'll need a new plan.

I did find a page that talked about how you can reverse the alarm setting so
that it switches off when the temperature falls within the target zone.  If
true then that has promise (and only needs a single NPN transistor).

The OP might find this interesting -
http://www.neufeld.newton.ks.us/electronics/?p=537.  The display is attached
by cable to the rest of the electronics, so it can be shoehorned into a
shallower (if wider) box.

These auto-tune as well.

Tony