temp controller/switch for power outlets

Ok, so I'm thinking of building a temp controled switch for houshold power outlets. It will be used for heating snake cages. It will have to have an external temp probe and a variable temperature shut off/on range, somewhere between 65 and 90 degrees F. I've looked at several ways of doing it ranging from rigging up air conditioning thermostats all the way to complicated circuits. Ayone have any suggestions on how to do it using what we in the Aircraft Electrician world call the K.I.S.S. (keep it simple stupid) method? I know they make them fairly cheap and I already have one of the said cheat ones. It's highly inaccurate and doesn't even switch on and off half the time. So I would like to make it and know for a fact that's it's a good solid piece of electrcial equipment. Thank you for your time.

Smitty

hi,
I would suggest a LM35 temperature IC, a LM393 dual comparator and SSR [solid state relay], powered from a 12Vdc wall wart type psu.

This might be a dumb question, however, how would I use the LM35 with an external temp probe? I don't want to put any electronics inside the cage itself.

Place the LM 35 in the cage, in such a way that heat doesnt escape..i.e seal the hole up for the leads to exit the cage...( the sensor could be encapsulated into a 'probe that is inserted into the cage , as you would a temperature probe)

As for the electronics, use the op amp as suggested by Eric to make a comparator, this drives the solid state relay that switches the heater on/off...All of the electronics is external except for the sensor or probe as you put it.................

Here is a circuit which is close to what you need. This one Makes on temperature rise; you want the opposite, easy to change. This one is for lower temperatures, but that is easy to change, too. This one drives a relay; substituting an SSR is easy.

I suggest you buy a $5.00 aquarium heater or a $10.00 room heater. You can find the room heaters for $2.00 in the op-shops.