Hi Shing,
Is that the one described here?
**broken link removed**
I take it this is just an excercise to demonstrate
effective handling of the unit ?
Basic safety, on the door sensor, use a normally open
pair which close when the door closes, the intention
being that if the wiring fails along the way, the bulb
and fan will not operate.
Bear in mind that the kiln (or whatever) is likely to
be controlled at a distance, and the person in control
at the display end may not be in a position to even
see or hear the unit under control, your display should
include not only an indication that the door is closed,
but an indication that the door is open, if that has to
come from the same sensor, that sensor should have both
conditions relayed back to the display.
Where one function such as cooling from a fan is the
opposite or complementary action to another function
such as heating from a lamp, care should be observed
in the setting of the controls. Try to leave an area
or range between them, so as the fan doesnt come on
as soon as the lamp goes out.
Try to relay as much information as possible back to
the display, even if it seems unnecesary.
There should also be indication at the kiln end of
when it is under distant control and liable to run,
not just an indication that its running.
Best of luck with it,
John