With the perfect weather we are having down south
, well perfect for doing projects I've put the time to good use with this badly needed addition.
I started by building a prototype pure PWM unit with 555 timer switching a power Darlington transistor. This was just 12v on off with a variable duty cycle and it worked fine so I thought ok I'll tidy it up and make a four unit setup but I soon found the cost of all the bits and in particular the PCB was prohibitive.
Price wise I could get ready made units complete from our friends in China for $6.50 each and free postage if I bought five. It was gunna cost that much just make the PCB's here at home so it was a no brainer really.
Put it all to the test on Saturday night and although it appeared clear the moisture levels were very high and that became evident after the moon came up as the sky glow in a few images I was playing with was very evident.
All in all though the dew control worked very well controlling two scopes and guide camera as all stayed clear for the three to four hours I was out.
The units I wound up with were sold as PWM units but are a bit of a mystery as the chip has no identifying marks and it also includes a 12V reg and a Power Hexfet/Mosfet so it is 0-12V regulated possibly with high speed switching PWM because that is what the Mosfet are used for.
Not sure about the PWM but testing the units proved to work just as well as the home made prototype so it didn't matter either way but there is a benefit of lower current draw as they are turned down so a smoother operating unit in the end.
Put the lot into this weather proof case and used gold connectors to stop corrosion problems from dew and the only issue was the red LED's lit up like a Christmas tree so will have to dull them down a little but very happy otherwise as works a treat.
The completed unit fitted neatly between the scopes with easy access.
Still using home made dew straps so the next step is to make better ones of those as currently they are stuck to the scopes, be nice to be able to remove them easily for whatever reason.
The first image is the prototype I made.
Chasing something like this myself for both TEC and a dew controller 
Jaycar need a kit like it i know they have the cooler/heater controller but this would be great for tec and dew point cooling.
