I thought this thread died and went to the thread-afterlife.
I haven't tried the jaycar one. I finally put the latest version of the dew heater described in this thread on github
https://github.com/ChrisV77/Telescop...aterController
It has two possible ways to calculate dew point. They are the standard formalae (at least as far as I know).
This project used a tiny 128x64 display. I noticed a lot of people use the 16*2 or 16*4 displays. I'll do another version for these in a while - but I still reckon that little display is way better !!!
I've now stuck mine in a larger box which also has 12v outputs, usb power out, a usb hub. So its all in one thing.
Chris