Here's what I used....
1 large polystyrene box used to transport tropical fish (begged from pet shop-free!)
1 thermostat kit from velleman (with highter rage thermistor) £10
1 12v downlighter kit with 25w bulb (£2-ebay)
1 wine making thermometer (already had)
2 brackets for thermometer( £2 fish shop)
Weld mesh panel for floor (£3 from B&Q)
wooden floor supports (already had)
cake tin for water (to go under the floor)
1 piece plexiglass for viewer
I put together the electronics kit in one afternoon- it was really straight forward as it's for kids use as an educational thing so it comes with full instructions. Wired up the transformer to bulb and board. Made holes in the box- for ventilation and to put the light in. Then I cut a ledge in the lid to fit the viewer in and taped it down. Measured the floor and cut a piece of weld mesh the same size and fitted supports cut from wood to lift the mesh off the floor and the cake tin can slide under. Fitted the thermometer and tested! IT WORKS!! I can maintain a constant temperature! WOW,
Full of pride in my own ingenuity
kind thoughts
Deb

Assembled bits- black box is 12v transformer.
Close up of thermostat. Wire with blue bulb is the thermistor- I have now added a longer wire so the unit sits outside the box

