Ending the temperature issue on allsky cameras #1013
Replies: 17 comments 18 replies
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@astrodan02 Dan, Someone, I think on the Allsky Facebook page, is using a cooler. I don't remember the details though. Is your camera getting extremely hot? Many people, myself included, use a temp controlled fan which helps keep the Pi and camera cooler. Do you have a design in mind? |
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I'm in Northwest PA, so, cooling is not a problem now, but when summer comes along it could be. Besides, maintaining a relatively constant temperature year 'round would go a long way to extend camera life. |
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Expanding some on the idea of a totally temperature controlled interior temperature for the allsky camera, I am thinking of using a stepper motor control module as the means of controlling the TEC voltage and polarity. Such a controller avoids the use of mechanical fans or relays which introduce dirt into the optical system. A totally enclosed system, while it clearly would require more circuit design, should extend the outdoor operation of the allsky camera without requiring service visits. |
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I just got mine together and working, it is winter here and im already seeing 140F on processor and camera, would just a filtered vent help? my box is tiny and also black (to reduce reflections in the dome) but i considering a larger white box and painting the top black. |
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@aughtago Yes, I think you already realize what the interior temperatures will be after a full day in the sunlight. I also thought of the box and its color. As you can see, I chose white for a box color, but even so, heat will be building up inside. Ventilation by a screened vent is good for heat dissipation, but will allow condensing moisture on colder nights to potentially enter, and, it does nothing to keep snow off the dome. Hence, I am looking at a box your size to house the pi, a stepper control module, a DHT22, and the TEC heater/cooler. The TEC assembly would be mounted along one side wall with a heatsink on, both, the inside and outside. |
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I like the idea of active cooling with the TEC. Although in my case I would have to add 12V power (I run Pi off an POE hat), but I have 120V close by. |
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this one might work too. its half the price and we only need 2 relay's , description says its only good for 5A at 30VDC, west the pic says 10A. |
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I like where we are heading. Some metal sheeting, or heatsinks, a board or two, and a TEC or TECs. I ordered the HiLetgo temperature controllers and think I may just use them with 2 separate TECs. Its not what I originally suggested, but, it will be fast and easy to add. As for needing 12V, I'm ok with that. One other advantage if we get this working and stable... focus should remain almost constant. |
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one thing occurred to me, is that the code should also monitor ambient temps, and maintain the enclosure temp a little above ambient to prevent dew on the dome. it of course would have to sacrifice dew prevention if enclosure temp was exceeding some set value. I have not used a DHT22 before, will it interface with the pi via the GPIO pins? if so it wold be a lot cheaper than the sensor hat that i linked. |
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Ultimately, I believe use of #830 with some modifications for a heating and cooling cycle can result in a less expensive alternative. However, this does increase the cpu loading and memory usage. In my present system, Pi3 1 GB with RPiHQ, I am already seeing what might be issues with swap size. |
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I have been watching this with a lot of interest What would be examples of the TEC's would one get for this? |
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This comes down to size and type of case, insulation, TEC, and your own local outdoor temperatures. But based on most cooled ccd cameras, I'd like to be thinking 5amp or so. |
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Any ideas on what I should start out with TEC and heat sink? I have the average size box that most of us are using for housing. I have looked on Amazon and there is a lot to select from. |
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I think that is a very important question. Personally I have never used a TEC before. I was reviewing spec sheets for a TEC1-12706 trying to understand that very question just the other night. The first unit listed that catches my attention is DTmax(C) which is described as "Temperature Difference between cold and hot side of the module when cooling capacity is zero at cold side" which to me sounds like the maximum temperature difference that it can still function? here is the data sheet I am looking at. https://espressomilkcooler.com/wp-content/uploads/2015/03/TEC1-12706-site-ready.pdf |
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Other thoughts and questions: How do we deal with the condensation that is liable to occur on the cold side (in our box)? Would a large desiccant remove enough moisture from the environment to prevent the condensation? Sealing the TEC where the heat sink passes through the box may be difficult and could be a source of rain entry. The TEC should be installed on the shady side(north for those of us in the northern Hemisphere) or under the box. I saw a TEC product kit that uses a fluid to transfer the heat, it has a tiny pump and uses 3/16" tubing which would greatly reduce the sealing effort for 2 small tubes passing though the box instead of a heat sink. |
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Today, I received the temperature control modules. They are nice and small, work on as little as 8.5V and could be modified to work at 5V if the relay was changed out. |
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my concern of condensation was because in cooling mode the cold side of the TEC can get VERY cold. However as I think about it, I have operated mine in single digit F ambient temps, and there was no observable condensation on the underside of the dome. I agree cooling is the main (maybe only) reason for the TEC, as said above I've operated mine in very cold temps and the heat from the PI has kept the unit very warm, no condensation on outside of dome, and even when it rains the drops evaporate very soon after the rain ends. I have been doing more research on capacity requirements and have found the following (for my setup, your mileage may vary) -Pi 4 power consumption is 600ma (3W) I think I will use 35 as max ambient, and 21 as inside target, so DT of ~15 anyone know how to read this? please provide feedback. |
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Today , I had a totally different thought. Very simple, not sure if it goes far enough to cool summer temperatures but here it is. Mount the PI in it's own box. It is the main source of heat and can stand up to 85C before it starts to modulate volts and amps. Connect plastic conduits between the two boxes(air ducts), one mounted high , one mounted low. Attach a PI fan to the high conduit blowing toward the camera box. Ideally a gravity louver mounted on the lower conduit(I can't find any, may need to be 3D printed). Let the Pi control the fan speed upon camera sensor temps or a dedicated sensor in the camera box. A third conduit that can be sealed with silicon would be needed for the USB cable and any temperature sensor wiring. pi fan |
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Interesting thread, i have a asi224MC in a grey box, Pi is inside without its box, only the circuit, and also a Pegasus powerbox which was to control the heat and fans. Quickly i noticed that the Pegasus was permanently activating the fan and the heat, resulting in condensation inside the dome, fans were blowing from bottom to the dome. So i disconnected the fans and the condensation disappeared. But now i think the heat is still working, so i will disconnect it also as the temp is now showing at 68°C for the sensor !!! |
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Although I am still working on the install, I intend to use some items I
purchased on Amazon.
(attached files have pics of the items) The problem is powering the
control modules requires 12V, which is taking up
more space than I allowed in my original case. My plan is to use one
module for cooling in summer and another
for heating in winter. Though the winter heating might be a non issue for
many.
At present, I do not use fians.
Dan
…On Mon, May 9, 2022 at 6:38 AM bemo47 ***@***.***> wrote:
Interesting thread, i have a asi224MC in a grey box, Pi is inside without
its box, only the circuit, and also a Pegasus powerbox which was to control
the heat and fans. Quickly i noticed that the Pegasus was permanently
activating the fan and the heat, resulting in condensation inside the dome,
fans were blowing from bottom to the dome. So i disconnected the fans and
the condensation disappeared. But now i think the heat is still working, so
i will disconnect it also as the temp is now showing at 68°C for the sensor
!!!
So... clearly i think there is a need to control the temp, i am in south
France and external heat can go up to 40°C, right now it is around 30°C,
and more for the allsky as it is fully exposed to sun.
But.... how to downgrade the temp inside the box ?
Fans will not be enough as they only move the air inside the box, so what
do u put inside the box to cool down the temp ? above TEC modules are
mentionned, do u have a link for such modules ?
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i gave a look at all items listed above, i can understand that we want to monitor the temp inside and activate either a heater or a cooler. To het 12V inside i have my Pegasus box but its quite big and maybe another solution like a Shelly Uni https://shelly.cloud/products/shelly-uni-smart-home-automation-device/ could be useful. Small, powered with 12V, 2 output circuits managed by an internal webserver, many sensors able to be connected, wifi connected. Nothing to prohram, you can implement a schedule, temperature limits, external conditions from other Shelly units, all done from the embedded webserver. |
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@astrodan02 or to make it short (now that i have fully read all above from the start....) : how do u intend to implement the TEC modules in order to evacuate the heat at the back of the TEC and avoid to keep the heat inside the box ? |
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Interesting thread. Like all refrigeration, a TEC is just another heat
pump. My Raspberry Pi is already in a metal case of the type which serves
as a heatsink for its circuitry. By having my Pi inside a metal case which
serves as its
heatsink, A TEC in contact with that case would be most efficient in
negating the heat the Pi contributes to the inside. This then is placed
inside a larger watertight box with the TEC, itself, mounted in the wall of
the box such that its external heatsink can dissipate the heat to the
atmosphere.
To minimize the cooling requirement I keep my power supplies in a separate
box not attached to the Raspberry Pi and camera.
Right now, though, I have been having more trouble with keeping the wiring
waterproof. :-(
Dan
…On Mon, May 9, 2022 at 4:11 PM bemo47 ***@***.***> wrote:
@astrodan02 <https://github.com/astrodan02> or to make it short (now that
i have fully read all above from the start....) : how do u intend to
implement the TEC modules in order to evacuate the heat at the back of the
TEC and avoid to keep the heat inside the box ?
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@astrodan02 hmmm, but for me i have a plastic box, or PVC, so if i put a TEC module inside, i should find a way to get the hot side communicating with the outside, the bottom of the box could be a good option as it is always in the shadow, not directly exposed to the sun ? |
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Finally after discussing with a friend who has some good knowledge about all ways to lower temp inside a computer or any box, he is not really in favor of peltier modules, he says that they are a bit difficult to control and adjust. But he is recommending a liquid cooler, same as we install in computers. In this way we can put the pump inside the camera box, maybe in contact with the back of the camera, two conduits goes to a second box below with the Pi and the radiator itself on the bottom of that box and the fans pushing the air outside the box. We must keep some holes to bring external air inside when the fans are blowing outside. In this way we could maitain the camera box at the same temp as the external temp or close. An if really needed a Peltier could be added for very high temps ? I am wondering if the Allsky camera temp control could be used to manage the on/off for the cooling system ? Could this be an interesting idea ? |
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@bemo47 A liquid cooler sounds like a lot of work with potentially the same results as just a fan. The back of a camera is not really close to the chip so zI don't think it would help much to have the cooler contact the camera. Are you trying to cool the sensor, the Pi, or both? |
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@EricClaeys |
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@bemo47 45 C seems pretty low. My sensor with a fan is 50 - 55 when 28 C outside. I blow the warm air up into the dome, and the down and out to keep dew and ice off. But, my camera is in the mountains of the Southwest US so is pretty dry. |
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@EricClaeys here i was blowing air up into the dome also but i had dew all the time due to this air pushed on the inside of the dome. And the box is hermetic, so the air is blown up to dome but stays inside the box. So i stopped the fans, now i don't have any dew. The environment here is pretty humid. But blowing inside the box doesn't have any effect on the inside temperature, or i think so. I am a bit hesitant between creating an air flow from outside to inside and then i could have an impact on the inside temp, but i could have dew... or staying with a closed box and having high temps inside... I think i will try external air input.... and remmoving some components from the camera box, mainly the pegasus not useful now, and also the small 12V-5V converter which can heat also |
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@EricClaeys i opened the box of my allsky. There two components heating too much, the Pi4, very very hot, i cannot put my fingers on the radiators, definitely the Pi4 should be outside of the box, and the voltage converter 12v-5v to power th Pi4. So my first action will be to externalize the Pi and its power, the consequence will be that i need a long USB cable from the Pi to the camera. And sorry for the original post.... i have the feeling that i am a bit outside the topic now... |
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I'm interested in the topic of temperature control. My box is made out of black petg with a 4" acrylic dome. On a 91°F day I got a 40° rise with an empty box that didn't have a rp4 or camera in it. Black was a good idea last fall when I built it. Now not so much. I'm printing a new lid out of white petg, making a mask to cover part of the dome and I'm moving the camera closer to the top of the dome. I was playing with some peltier chips but they seem to be 5% efficient so I gave up on that for now. I'd have better luck putting a heat exchanger in the camera box and burying some copper tubing in the ground and pumping water. Air vents are another idea with some fans. I'm still thinking about it. If I'm having issues at Lat 45N others, closer to the equator, have to be having more problems. I'd love to hear what you did to deal with heat. |
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I too had a small black box at first, temps were crazy high in the winter, especially in the day time. I have moved the gear into 2 larger white boxes, with the Pi(main source of heat) in one box and the camera in another. I connected the 2 boxes together so that a little heat can keep the dome clear. I plan to add some cooling but haven't got that far yet. in the meantime , I only run the camera at night, temps are much better than they were before, but just hitting warm temps here in the northeast, so time will tell. I also hope to set up a log of temps once i figure that out. |
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I agree fully with use of a larger box to aid in keeping the temperature inside from heating too much. The larger surface area of box, coupled with a larger inside air volume tends to buffer temperature changes. Additionally, this facilitates consolidation of the Pi, camera, and temperature control circuitry. |
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Reading through many threads I see the need for temperature control of the camera environment. Many suggest only heating as the answer. I feel this approach only addresses half of the problem faced by many. My suggestion is we utilize a small TEC to control the temperature totally. This means, the device would cool the inside when outside sunshine overheats the camera. And, in cool times, or freezing, it would heat the interior.
I know this programming sounds complex, but, just a thought.
Dan
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