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Leon,
I just bought a 5-in dew heater strap for my ETX from Bintel .. it was $79. Seemed easier that dealing with resistors and nichrome wire.
As I have an existing Jaycar QM???? temperature measuring meter (which gives the temp difference between its two thermocouples) my idea was to just keep an eye in this and manually switch the heater on and off to keep the corrector a few degrees above ambient. The controller could come later if (a) the manual method didn’t work, and (b) if I won the lottery.
However, was in Jaycar recently and couldn’t stop myself buying the 12V Motor Speed Controller kit (KC-5225) for $23.95 (essentially a PWM device) and a UB3 box. I was in a rush so didn't get any other associated bits (cig socket, switch, LED).
Haven't tried the dew heater yet, and haven't built the kit, but will do soon.
The kit includes a tiny trimpot on the circuit board to vary the pulse width, so I imagine I'll be back at Jaycar to find a substitute variable potentiometer with knob to fit onto the box.
The kit looks fairly simple to make up and handles 10 amps (more than enough for the heater!). Dick Smith sells something similar I believe, but it may be of lower maximum amps.
The only reason I’m saying all this (much of which you probably already know) is to suggest it may be easier to buy this kit than get all the parts separately.
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