All Sky Camera Dew Heater Power?

[kbrown]

Hi,

So I'm finally actually putting together an All Sky Camera which has been on the bottom of my To-Do list for way too long. It's going to be a RPi3 + RPi HQ camera based and powered with a 5V/2.4A PoE splitter so I don't have to run multiple cables. I'll be running my dew heater off of that 5V as well. My question basically is what do you think is the minimum adequate power for the dew heater? I'm thinking of using just nichrome wire ring around the camera inside the dome as I've got plenty of that available. Something like this:

The thin yellow torus represents the dew heater. As a test I cut off about a 20cm long nichrome wire which is about the circumference of the torus and applied 5V from the ends of it. It drew about 350mA (1.75W) and did get warm to the touch but not too hot I would have had to let go. Do you think this will be enough? The diameter of the dome is about 10cm.

I'm trying to keep the power consumption down as in the future I'm hoping to add weather station functionality to this as well and run all the peripherals from the same power supply.

 

Edited August 21, 2023 by kbrown

[DaveL59]

In one of my domes I use some ceramic resistors that are fed 12v, can't recall the spec I went with now but it should be on the el-cheapo sky cam thread. The camera itself is a USB webcam innards and other than snowy nights the dome has been kept clear of fogging up without using lots of heat. I do have it fed via a temp and dawn/dusk controller that's external so its only on either at night or below a set temp.

One day I may replace the camera part with either a spare Logitech C720 or stump up for a proper astro unit, but the way the skies here are more grey than black now I'm not sure its worth doing any more.

[tomato]

I think the one that @Tomatobro put together for me pulls about 4W, the base plate is just warm to the touch on a 0 to +5 deg C night. One key factor is the seal of the clear dome to the base. The o ring used initially was slightly too small an OD, and ingressed moisture just kept condensing on the inside apex of the dome. A slightly thicker o ring fixed this.