DIY Budget Dew Heater Cotroller

To prevent dew from forming on my guide scope and main imaging lenses I decided to make a quick and cheap dew heater, The controller is basically a Pulse width control PWM DC motor speed regulator controller switch 6V-90V 15A that I purchased from eBay for £4.46p, it is housed in a project box and powered by 12v DC, by using a ready made circuit board there was minimal work with only the power lead, Phono sockets, switch and LED to solder.

Here is a view of the inside of the project box showing the simplicity of the connections, the PWM board and layout, I could have got away with using a smaller project box but as I already had this one and wanted to keep the cost to a minimum that's what I used.

I also made my own DIY dew heater bands, one for the main 400mm imaging lens and another for the 135mm guide scope, I used nichrome wire cut to a length that gave me a resistance of 17-18 OHM's, this was looped onto a piece of camping mat and covered with good old gaffer tape, the second heater band was made using 330 OHM resistors wired in parallel, again laid out on a piece of camping mat and covered with gaffer tape, both heater bands were attached to phono cables.

The second heater band.

The PWM motor speed regulator that I used.