AllSky camera nightmare….help….

[Stuart1971]

So a few months ago I built an AllSky camera with an RPI4 and the RPI HQ camera and all worked very well, it’s in a 125mm square sealed project box, with a dew heater ring around the lens in the dome area, but having real issues with condensation inside the dome, now I have read a few threads on here and other places about this issue and have followed some advice, bit to no avail, in fact it’s worse.. 

I should add that this is mainly after rain that the issue occurs, it seems fine at other times…

I have added a 40mm fan on one side pulling air out of the unit, and a 40mm hole on the opposite side for air to be drawn in, to try and ventilate the unit, the RPI4 does generate quite a bit of heat, and have tried with the dome heater ring on and off, and seems better with it off, but can’t lower the heat any more as this comes from the RPI

The dome area is open to re rest of the unit and not sealed off at all..

The air is obviously warm and condensing on the inside of the dome, but many others use this same set up without issue…so not sure what to try next..

Any ideas…

Edited March 27 by Stuart1971

[AstroKeith]

14 minutes ago, Stuart1971 said:

So a few months ago I built an AllSky camera with an RPI4 and the RPI HQ camera and all worked very well, it’s in a 125mm square sealed project box, with a dew heater ring around the lens in the dome area, but having real issues with condensation inside the dome, now I have read a few threads on here and other places about this issue and have followed some advice, bit to no avail, in fact it’s worse.. 

I should add that this is mainly after rain that the issue occurs, it seems fine at other times…

I have added a 40mm fan on one side pulling air out of the unit, and a 40mm hole on the opposite side for air to be drawn in, to try and ventilate the unit, the RPI4 does generate quite a bit of heat, and have tried with the dome heater ring on and off, and seems better with it off, but can’t lower the heat any more as this comes from the RPI

The dome area is open to re rest of the unit and not sealed off at all..

The air is obviously warm and condensing on the inside of the dome, but many others use this same set up without issue…so not sure what to try next..

Any ideas…

There are many different approaches!

First how much power are you putting into the dew heater? The holes in the sides, are they protected from rain and dew? It would be more usual to have them in the bottom.

If it's an open box, I'd suggest not having the fan on, and the heater on max power. Otherwise the heater is going to fight a losing battle with fresh damp air coming. You want the heat from the dew heater and Pi to build up inside the dome.

My own version is sealed. It has a dew heater and silica gel packets which I change every 3 months or so.

[Stuart1971]

7 minutes ago, AstroKeith said:

There are many different approaches!

First how much power are you putting into the dew heater? The holes in the sides, are they protected from rain and dew? It would be more usual to have them in the bottom.

If it's an open box, I'd suggest not having the fan on, and the heater on max power. Otherwise the heater is going to fight a losing battle with fresh damp air coming. You want the heat from the dew heater and Pi to build up inside the dome.

My own version is sealed. It has a dew heater and silica gel packets which I change every 3 months or so.

Well it was sealed with RPI and dew heater filling the unit and dome with heat, and was fine until it rains, which causes the dome to cool and condensation to form, from all the warm air inside, how can this be stopped during rain..?

it was because if this I added the fan and extra hole on opposite side, which have grills on the outside to stop rain entering and a foam on the inside to stop bugs and such like.

It actually seems a bit better with less heat inside. ie, when I disconnected the dew heater ring..🤔🤔

Edited March 27 by Stuart1971

[Ratlet]

How much space is there inside?  Could you try to more effectively seal it with some dehumidifier packets inside?

[Stuart1971]

49 minutes ago, Ratlet said:

How much space is there inside?  Could you try to more effectively seal it with some dehumidifier packets inside?

Yea, have tried, it was fully 100% sealed when I first built it, with desiccant and still was the same when it rained…

The rain will always cool the dome, so if there is warm air inside it will always condense….right..?  no idea how other people deal with this issue…🤷🏼‍♂️🤷🏼‍♂️

Edited March 27 by Stuart1971

[Stuart1971]

Ok, so sealed the unit again and as soon as I put it back outside the dome is misting up from the heat inside, so having it sealed is not the answer…

I have read loads of posts about this and the consensus seems to be to have heat and ventilation, which also does not seem to work, so I am at a total loss…☹️

[AstroKeith]

If it truly sealed, and has desiccant, plus a dew heater, it cannot mist up. All three are required (sealed, desiccant, heater)

Or as I said, the ventilation holes must be underneath, no fan, reasonable high power to the dew heater.

[Tomatobro]

My allsky has 25 watts of heat going into it and when its switched on in the evening the dome will show a degree of misting some nights. After about an hour its clear.

I read somewhere that someone tried reducing the volume of air  inside the canister by packing it with high density foam. The idea I think was that as its the air that is holding the moisture then reducing the volume inside with the foam it reduced the amount of water available.

I have packed the housing that holds my Unihedron SQM meter and it seems to have worked but have not tried it with my allsky.

[Stuart1971]

52 minutes ago, AstroKeith said:

If it truly sealed, and has desiccant, plus a dew heater, it cannot mist up. All three are required (sealed, desiccant, heater)

Or as I said, the ventilation holes must be underneath, no fan, reasonable high power to the dew heater.

Hmmmm,  when you seal it there is air sealed inside, this air will have moisture in it, and as soon as the power is on, the air warms up, then hits the dome on the inside  which is cold as it has cold rain falling on it, so the warm air condenses on the inside of the dome, then drips down, re evaporates and condenses again, in a cycle…

why do the holes need to be underneath and not on the lower sides..?? As long as they dont let water in…?

[AstroKeith]

1 hour ago, Stuart1971 said:

Hmmmm,  when you seal it there is air sealed inside, this air will have moisture in it, and as soon as the power is on, the air warms up, then hits the dome on the inside  which is cold as it has cold rain falling on it, so the warm air condenses on the inside of the dome, then drips down, re evaporates and condenses again, in a cycle…

why do the holes need to be underneath and not on the lower sides..?? As long as they dont let water in…?

That is why the sealed version has desiccant. It reduces the RH of the internal air to about 10-20% which reduces the dew point to a figure that cant be reached. ( I used to design optical equipment for the services)

Rain is never truly vertical and anyway will run down the sides of the box. So your vents, grills and foam will be damp at best, soggy at worst. The Starlight Xpress Oculus all-sky camera uses holes underneath I believe.

[Carbon Brush]

A sealed camera case is a good solution. It is my preference.

First check the state of all the weak points. Clear dome to box gasket. Box lid to body gasket. Lid screws are outside the gasket.
Any PCB fixing screws that pass through the wall muct be sealed. Cable exit via well compressed glands - not connectors, etc, etc.

If you reckon the box is well sealed, put a bit of tissue paper in there - not the camera.
Give it a blast from a pressure washer. Not too close, but simulate a gale and intense rain day.
This also simulates wet air being present at higher pressure than inside air.
Dry off the outside. Open up and check the tissue paper is good as new. If not look for the leak.

Silica gel absorbs only a small amount of water for it's mass.
The amount of water held in air is temperature dependent and not a simple straight line.
I read somewher that a 1C rise in temperature can allow 7% more water in air.
Then how do you know it the silica gel is dry to start out? Are the bags new and from an assured source?

Pop the bags (yes quite a few) into an oven at a little over 100C for several hours. Yes hours.
That ensures all moisture is driven off. Unfortunately some bags melt their glue. But the product is cheap so don't worry.
Immediately, while hot, put the bags into a biscuit tin or similar. For long term storage this way, add sellotape to seal the lid.

Now take your camera outside, on a cold day. There won't be much moisture in the air - unlike your warm house with pans boiling on the stove, humans exhaling, shower running, etc.
Stuff as much silica gel into the camera as you reasonably can and seal it.
Lots silica gel ensures you can absorb a lot of water and leaves little space for moist air.
I reckon that should do the trick.

When diving and snorkelling in the sunny parts of the world, I avoided condensation by storing my cameras and open housings in the fridge.
Immediately on removal from the fridge, the camera was sealed into the housing with of course little air space.
This alone was a very good condensation preventor.

HTH, David.

[Stuart1971]

1 hour ago, AstroKeith said:

That is why the sealed version has desiccant. It reduces the RH of the internal air to about 10-20% which reduces the dew point to a figure that cant be reached. ( I used to design optical equipment for the services)

Rain is never truly vertical and anyway will run down the sides of the box. So your vents, grills and foam will be damp at best, soggy at worst. The Starlight Xpress Oculus all-sky camera uses holes underneath I believe.

The vents are truly sealed now trust me, I have sealed inside and out of them, the box is a water tight version with a rubber gasket seal on, and the dome is sealed to the box too, the cable inlet is also totally sealed, and there are 8 desiccant packs in there, the RPI produces a lot of heat, and there is a heater ring also in the dome area around the camera, and still this is the image from the camera and it’s not raining….☹️

The dome is soaked on the inside…

Edited March 27 by Stuart1971

[Stuart1971]

And here is what the unit looks like, the lid screws are outside of the lid seal.

 

[AstroKeith]

Well, the air in the box is saturated with water. That for sure. So either,

The desiccants are saturated and/or not enough (a 50 gem pack is about minimum.

It isnt sealed.

Carbon Brush gave good advice, I wouldn't cook my gel at 100C  though. I find 60 for 2 hours enough.

[Stuart1971]

2 minutes ago, AstroKeith said:

Well, the air in the box is saturated with water. That for sure. So either,

The desiccants are saturated and/or not enough (a 50 gem pack is about minimum.

It isnt sealed.

Carbon Brush gave good advice, I wouldn't cook my gel at 100C  though. I find 60 for 2 hours enough.

Well I give up then, as the desiccant was new and unopened and perfectly orange and not green as it is when saturated…

I have 200g in there, and the box is sealed…and it’s far worse now with the box sealed, than it was before I sealed it and had it was vented, as then it only dewed up when it rained, now its  like it all the time…

I am totally out of options..🤷🏼‍♂️🤷🏼‍♂️

[AstroKeith]

If you open it now, what colour is the silica gel?

It clearly isnt working as a desiccant, or it is saturated. already -  Laws of physics.

[Stuart1971]

Just now, AstroKeith said:

If you open it now, what colour is the silica gel?

It clearly isnt working as a desiccant, or it is saturated. already -  Laws of physics.

Orange, and it turns green when wet…it was brand new several hours ago when I put it in,  use it on other things and works really well, so I know it works fine…

[Stuart1971]

4 minutes ago, AstroKeith said:

If you open it now, what colour is the silica gel?

It clearly isnt working as a desiccant, or it is saturated. already -  Laws of physics.

The laws of physics also say that to prevent condensation you need heat and ventilation, so a sealed unit may not be the answer..As it is far worse now than it was before it was totally sealed…

Edited March 27 by Stuart1971

[AstroKeith]

21 minutes ago, Stuart1971 said:

The laws of physics also say that to prevent condensation you need heat and ventilation, so a sealed unit may not be the answer..As it is far worse now than it was before it was totally sealed…

Not so. A cold surface (your dome) will attract condensation if it is colder than the dew point of the air inside. Warm humid air (ie air from outside) will have a high dew point and be likely to condense. To stop this you would have to blow enough air through to dry off the surface - a lot.

Its quite simple, you are getting condensation, therefore the air inside is not dry, therefore your desiccant isnt working in this instance

[Ratlet]

The desiccant isn't a magic bullet and needs time to work.  Or at least time to work before the water condenses out.  I think your desiccant is working, it just needs time.

If you are sealing the unit in a warm location (like inside) the air inside the box will be loaded with moisture and will need time to dry.  In this case you need to leave it for a while, sealed with the desiccant to dry out whilst it is still warm.  If you take it out to the cold before the desiccant dries the air then the moisture will still crash out of the air when it cools down.  

[Stuart1971]

16 minutes ago, Ratlet said:

The desiccant isn't a magic bullet and needs time to work.  Or at least time to work before the water condenses out.  I think your desiccant is working, it just needs time.

If you are sealing the unit in a warm location (like inside) the air inside the box will be loaded with moisture and will need time to dry.  In this case you need to leave it for a while, sealed with the desiccant to dry out whilst it is still warm.  If you take it out to the cold before the desiccant dries the air then the moisture will still crash out of the air when it cools down.  

Does it not make sense that if the air in the dome is warm then when it hits the inside of the cold dome it will condense, but if the air in the dome is cool pretty much as cool as the dome, then no condensation will occur…🤔?

I ask this because I can seal the dome chamber completely so it’s not linked with the air in the box itself, as this may help, and not heat this air in the dome…or I could leave the heater ring in the dome on, which would be best, heat in there or no heat..? also I could put a couple of desiccant packs in the dome too…thoughts…?

[DaveL59]

2 hours ago, Stuart1971 said:

And here is what the unit looks like, the lid screws are outside of the lid seal.

 

Now for me, I'd have assembled that with the box the other way up so there's no chance of water pooling in those case screw areas and potentially seeping in. I also put clear RTV into the holes thru the dome lip to prevent ingress, tho in my case I used a CCTV metal bell housing inverted. You only need the tiniest gap for water to wick into the housing which will defeat the dessicant very quickly.

For a dew heater I just have a few ceramic resistors in series where you have the fancier circuit board and it doesn't fog up unless temps get really low and snow settles. Then again I'm not using a Pi but a USB camera so far less heat involved.

[tomato]

I have internal heaters and desiccant and supposedly a well sealed system but my all sky cam is always dewed up big style in the winter, both on the lens and inside the dome. Moisture must be getting in but the enclosure is totally soaked every time it rains so it wouldn’t take much of a seal problem to get enough moisture inside where it is not wanted.
I have just ordered a Dew Control ring heater to see if that will help as it will be closer to the condensation but I see you you already have one fitted…

Next step will be some kind of forced air ventilation, but that will be tricky as there will definitely be a route for water ingress with that installed.

I might also try a secondary water barrier by putting a water proof bag over the unit when not in use.

[Stuart1971]

2 hours ago, DaveL59 said:

Now for me, I'd have assembled that with the box the other way up so there's no chance of water pooling in those case screw areas and potentially seeping in. I also put clear RTV into the holes thru the dome lip to prevent ingress, tho in my case I used a CCTV metal bell housing inverted. You only need the tiniest gap for water to wick into the housing which will defeat the dessicant very quickly.

For a dew heater I just have a few ceramic resistors in series where you have the fancier circuit board and it doesn't fog up unless temps get really low and snow settles. Then again I'm not using a Pi but a USB camera so far less heat involved.

Those case screw holes go all the way through to the bottom and have a hole all the way through, they are as.o outside of the internal size of the box and outside of the seal around the lid, so no chance at all of any water ingress from there…and there is also a seal between the dome lip and case, and in sealant in those screw holes too..

[Stuart1971]

58 minutes ago, tomato said:

I have internal heaters and desiccant and supposedly a well sealed system but my all sky cam is always dewed up big style in the winter, both on the lens and inside the dome. Moisture must be getting in but the enclosure is totally soaked every time it rains so it wouldn’t take much of a seal problem to get enough moisture inside where it is not wanted.
I have just ordered a Dew Control ring heater to see if that will help as it will be closer to the condensation but I see you you already have one fitted…

Next step will be some kind of forced air ventilation, but that will be tricky as there will definitely be a route for water ingress with that installed.

I might also try a secondary water barrier by putting a water proof bag over the unit when not in use.

Sounds like you have the exact same issue as me…