Hello Everyone,

Regarding Allen Dicks question concerning the source for my temperature
controller. Temperature controllers use a thermistor to measure
temperature change. Switching is controlled electronically with
transistors rather than using contact points. This allows the temperature
differential to be set to rather small values not limited to the
mechanical  properties of a set of contact points.

They are used in process control, air conditioning, heating, etc. for
large buildings. I bought mine (Goldline Model SP-34)for about $60US from
Graingers, an industrial suppply company in the USA. Contact any
industrial supply company. Several less expensive models with more
functionality are being imported and may be available in your area

Best Wishes
Dennis Murrell