BlueWolf
Posts: 33
Joined: Fri Aug 25, 2017 8:59 pm

Keep the glass for the camera clear from snow and ice

Thu Dec 28, 2017 10:00 pm

tl;dr: I am looking for an easy way to keep snow and ice from a small piece of glass for a camera to look through. Everything is battery operated. What are my options?

Long story:

For one of my new projects, I am going to build a battery-powered Raspberry Pi driven video recorder based on motion (that's a mouth full). There are a lot of technical challenges, one of them are the incredibly harsh conditions it's going to face.

I will make a 3D printed case with a hole (covered with glass) for the camera to peek through. However I am looking for a way, a heating element of some sorts, to keep the glass from getting covered in snow and icing up. The only heating element I know is the heating pad from Adafruit:
https://www.adafruit.com/product/1481
But that is more an on-body kind of thing so I feel that might be a waste of energy? Are there any better ways for what I want, that I can easily make battery powered?

The extra challenge here are the conditions outside. It will be out there in the wild on its own, on a pole of some sort. And since I live in the Artic temperatures can sometimes go down to -40. I don't *know* if this will work yet, if the battery will even survive (it only needs to be on for an hour or two). But I want to start experimenting with it and see how much I *can* do. We get a huge amount of snow in the winter and I want the camera window always to be clear.

pcmanbob
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Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Keep the glass for the camera clear from snow and ice

Thu Dec 28, 2017 11:01 pm

Most commercial cctv enclosures use a couple of large resistors or a heating pad to keep the inside of the enclosure warm to demist/de-ice the viewing port, but they are almost all mains operated so can afford the wasting of energy in this way.
To operate at the cold temperatures you required will need a big heater which your battery set-up may not be able to support.

some example on this site : https://www.sourcesecurity.com/wipers-d ... aters.html

The pi its self may not operate reliably at those temps
WHAT IS ITS OPERATING TEMPERATURE?

The Raspberry Pi is built from commercial chips which are qualified to different temperature ranges; the LAN9514 (LAN9512 on older models with 2 USB ports) is specified by the manufacturers as being qualified from 0°C to 70°C, while the SoC is qualified from -40°C to 85°C. You may well find that the board will work outside those temperatures, but we’re not qualifying the board itself to these extremes.

the pi camera board is only rated down to -30°C
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BlueWolf
Posts: 33
Joined: Fri Aug 25, 2017 8:59 pm

Re: Keep the glass for the camera clear from snow and ice

Fri Dec 29, 2017 2:06 pm

pcmanbob wrote:
Thu Dec 28, 2017 11:01 pm
Most commercial cctv enclosures use a couple of large resistors or a heating pad to keep the inside of the enclosure warm to demist/de-ice the viewing port, but they are almost all mains operated so can afford the wasting of energy in this way.
To operate at the cold temperatures you required will need a big heater which your battery set-up may not be able to support.

some example on this site : https://www.sourcesecurity.com/wipers-d ... aters.html

The pi its self may not operate reliably at those temps
WHAT IS ITS OPERATING TEMPERATURE?

The Raspberry Pi is built from commercial chips which are qualified to different temperature ranges; the LAN9514 (LAN9512 on older models with 2 USB ports) is specified by the manufacturers as being qualified from 0°C to 70°C, while the SoC is qualified from -40°C to 85°C. You may well find that the board will work outside those temperatures, but we’re not qualifying the board itself to these extremes.

the pi camera board is only rated down to -30°C
Thanks for the input. I know that this is a challenging environment for the pi. But the price makes it worth experimenting with. I'm okay if I need to replace it on a yearly basis. I already have two Zero's outside controlling some lights. We haven't had -40 yet but it did hit -30 a couple of times and there were no temperature-related issues with those (Just a sticky mechanical relay that was actually easy to solve. I expected those things to break months ago..). The Raspberry keeps itself surprisingly warm. It's -18°C right now and one is reporting itself to be +8°C and the other +10°C.

I happened to come across nichrome wire and I'm looking into that as that seems like a great tiny DIY heating element that you can make in any shape (around the glass) you want.

I had a LiPo battery in mind but perhaps I should think bigger. A deep cycle battery maybe if the heating element really draws that much power. I'm probably going to experiment with both I think.

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Gavinmc42
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Joined: Wed Aug 28, 2013 3:31 am

Re: Keep the glass for the camera clear from snow and ice

Fri Dec 29, 2017 2:31 pm

Use a Pi3 they get warm enough ;) .
Using an insulated enclosure then any heat will go out though the glass window.
If you use something like a microscope slip cover, small disc, very thin glass, this could be mounted in an aluminum frame.
This frame could be heated with small resistors, if needed.
I use tiny RCD 2Watt wirewound resistors and have pushed them to 10watts to heat small alum blocks above 100C.

May need dry air or nitrogen filling?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

hippy
Posts: 5344
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Keep the glass for the camera clear from snow and ice

Fri Dec 29, 2017 2:59 pm

Mounting the Pi, camera and glass in the smallest enclosure you can build, insulated and placed within a larger enclosure, will maximise the amount of heat available for keeping things at a reasonable temperature and the glass clear.

As noted, CCTV cameras, street lights and the like are usually fitted with a heating element of some kind to keep ambient temperatures in the enclosure high. Without unlimited power you may have to experiment to find out how much heat and current you require, the best way to produce that, and what batteries it would require.

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