Cloth Heater from Amazon for 8 dollars keeps dome clear of dew

[jsalsburg]

Search Amazon for "USB Electric Cloth Heater". Shipped to me for $8, I put these heat pads on the floor of my AllSky Dome around the camera so they are exposed to the sky through the dome keeping it clear of dew. Altered the heating pads bypassing the manual switch so they are always on. They are supplied power through a seperate 12 to 5 volt car cigarette-lighter regulator to run the pads separate from RPi power. The 5 pads draw 1.8 amps at 5 volts. I tested the current when covering the pads stacked together and also inside small enclosure to determine if they would overheat. They self-regulate and do not overheat; no thermostat required. The next time I pull my Camera off its mast for maintenance, I will probably cut one out so there are 4 pads instead of 5. It does not freeze here in Lompoc so this solution may not be enough for frigid climates. However, stacking a second set of heat pads, 10 total, may be enough to keep a dome clear in freezing climates. Stacking 10 pads may require a thermostat to prevent overheating.

Thermal image of a single heat pad. Notice it is not too hot, only 128F.

Thermal image of all 5 heat pads in a yogurt container to check if they overheat, they did not. Notice outside temperature with all 5 together is only 136F, safely not too hot.

[EricClaeys]

Let us know how they work. Sounds like an interesting idea. How big is each pad?

[jsalsburg]

https://www.amazon.com/dp/B07K23GZB9?ref=ppx_yo2ov_dt_b_fed_asin_title
There are 5 of them, each approx. 11 x 7cm / 4.3 x 2.8 inches. You can see in my first thermal image the heat is coming from a thread sewn into the cloth. I cut out the controller, bypassing it, so they are on all the time.

[aaronwmorris]

If you cut 4 pads off (using only a single pad), you would be close to 0.4A total which the Raspi should be able to directly supply. You would be at nearly 2W of power which should be just about the perfectly sized dew heater. 9W is really too much power for an allsky camera dew heater.

[jsalsburg]

Yes I understand. Since I just started using these things I am sure I will modify using them some more.

[jsalsburg]

I made changes to my AllSky Camera. http://oceanave.ddns.net/
The original Heat Pads were 5 in number, drawing several watts from a separate 5VDC supply in the AllSky Camera enclosure. Yesterday I cut out 3 of the Heat Pads and plugged the remaining 2 into the RPi usb. Overnight, the RPi went into low voltage throttle. Today I returned the Heat Pads to their own power supply.
Additional changes...
Placed camera on rigid pedestal under the dome, raising it. This causes the dome to magnify the inside of the dome into the camera. This can only be remedied with a better shroud around the camera.
When the AllSky camera was on my workbench yesterday, I created the dark file for subtracting noise in low light conditions.

[Jsorace04]

I'm starting to run into issues with condensation inside of my dome, and I have dew every morning on the outside. I don't know if I'd be able to run a usb dew heater on mine since I'm running POE

[aaronwmorris]

There is likely power available to run a USB dew heater with POE, but you do have to be careful. A lot of USB heaters are designed for 1-2 amp USB chargers, however, the Raspi is only able to supply 0.5a on its USB ports. That is why I mentioned above removing 4 heater pads and running a single pad would be 0.4a, just under the 0.5a limit, which is perfect.

Unfortunately, a dew heater is probably not going to fix condensation inside the dome, in fact, it may make it worse. Condensation inside the dome means too much moisture in the air. Is your enclosure air tight?

[Jsorace04]

No the enclosure is not air tight. I'm still testing so the dome is currently secured with electrical tape around the bottom of the dome. So that "should" eliminate the condensation inside the dome.

The dew on the outside I will still need to tackle. Does our Allsky program have the ability to run dew pads automatically or is it a manual process? I was reading about it in the wiki on the webUI page but didn't understand if there was an automatic process for it

[jsalsburg]

My AllSky Camera is PoE but on independent PoE connectors. I am using an old Laptop Power Supply to power the Camera. I bought PoE breakout connectors for this purpose. Search Amazon "Passive PoE Injector and PoE Splitter Kit". Inside the Camera enclosure I rewired 2 car cigarette lighter 12 to USB converters, one to power the RPi, the other to power the Heat Pads. Be sure to position the Heat Pads to direct exposure to the sky as best as possible so their IR radiation is passing through the dome, this is what reduces Dew not just heat.
I placed large silica gel moisture packs in and under my dome. Replace the Silica packs every time you take down the camera for maintenance.

[jsalsburg]

The Heat Pads I recommended in this discussion are self regulating; they will not overheat. Unless you are operating a camera in freezing, and long duration icy conditions, the heat pads I recommended will suffice for most cameras in temperate climates. Dew Rings are made for telescopes and my be required for AllSky cameras in freezing climates and may require a thermostat to prevent overheating.

[jsalsburg]

I made changes and improvements to my AllSky Camera. Before this improvement I had 2 Car Cigarette Lighter USB Power converters in the enclosure. One supplying power to the RPi, the other supplying power to the DEW Heat Pads. I purchased (Amazon) a single Car Cigarette Lighter USB Power converter with high power Type C and USB sockets. This simplified power connections in the enclosure.
Additionally I purchased Black silicone Placemats; used 2 of them, one as a black anti-glare base for the dome and water seal, the other as a water-shedding membrane outside the dome; cut a hole for the dome to protrude through sealing the dome through the hole to shed water.

[jsalsburg]

This car charger comes highly recommended.
USB-C Car Charger, 3-Port 90W Fast Car Charger, Dual USB-C & USB-A Car Power Adapter...
https://www.amazon.com/dp/B0CZ9D6G26?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
I have not tested this charger with the RPi 5. This device is enclosed in aluminum. To adapt this charger to run the AllSky Camera, the bullet end that inserts in the cigarette lighter can be unscrewed where a spring can be unsoldered to solder a positive wire. The Negative wire can be soldered to the outside spring-loaded contact.