DIY dew controller and Telrad fix

[PeterHA (Peter)]

All,
Following ideas others have published in the past, here my cheap dew controller and Telrad fix.
Aim was to have only one cable from battery pack to mount and only one from mount to telescope.

I have build a small dew controller using a $4 LED dimmer from eBay (only PCB) a small box (8x5cm), it has two outputs for heaters (up total 48W) and one input for 12V and allows an 12V output for the Nexus on the mount, so only one cable from Battery for all equipment.
A LED ramps in brightness with heater output, the heater circuit has a fuse.
The thing will attach per velcro on top of my Nexus WiFi which sits on the mount.

Also a Telrad mod with permanently build in heater (2 resistors total of 2W), a connection for a second heater and a connector to the controller. This will allow me to connect a scope heater strap with a short cable to the front Telrad connector and the cable from the second connector to the controller is the only cable between scope and controller on the mount.

Start of my prep for the dewy weather.

[mikerr (Michael)]

Peter thanks for posting the setup and pictures. Neatly done.

One thing I would mention. I think the PWM controller might put spikes and garbage on the power rail. This will not cause any problems to the dew heaters
but may cause damage to more sensitive electronics using the same power supply. I'm not sure what Nexus is

My own system uses one supply for the dew heater and a separate supply for the Mount Electronics/Hand Controller.

Someone more knowledgeable than me might chime in or you may already be aware of the possibility.

Michael

[jamespierce (James)]

Don't forget to turn your german dew heater upside down so that it works correctly here in Australia.

[PeterHA (Peter)]

Well James,
I also switched the interface in our cars to German - one needs some sentimental reminders of ones heritage!