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Protecting USB ports from dew

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#1 Fukinagashi

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Posted 24 January 2020 - 10:03 AM

I use a miniPC on my TAK to automate my equipment (cold-mos camera, filter wheel, focuser controller, etc.).

All the devices are connected to the 4 USB ports of the miniPC.

Yesterday I had problems with my focuser controller (Starlight Instruments) that stopped working (ASCOM driver error: "Value was too large or too small for an Int16").

No way to make it work again (detached-attached USB cable on both side, rebooted the miniPC, etc.).

Today (at 13:30 CET) the device is back. I start thinking that dew could be a possible source of problems.

As I'm automatizing the whole observatory (currently in my garden) to move it in a better place this could be very annoying.

Any idea how to protect the USB ports from dew?



#2 happylimpet

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Posted 24 January 2020 - 10:06 AM

Not off the top of my head, but thanks for raising it as an issue - that may explain some issues Ive been having!


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#3 GrafikDihzahyn

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Posted 24 January 2020 - 10:30 AM

I use a large rubbermaid storage container that has holes for the cords. This way the laptop stays protected from dew and frost, while the dew controller and strips protect the scope.

 

Not my idea btw, I kinda stole it from Trevor Jones of Astrobackyard.

 

At the end of the night, most of my stuff gets packed into the same container for storage until the next outing.


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#4 Fukinagashi

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Posted 24 January 2020 - 10:45 AM

Thanks. The miniPC is piggybacked by the telescope though so I cannot go for Trevor tip.

 

 

I use a large rubbermaid storage container that has holes for the cords. This way the laptop stays protected from dew and frost, while the dew controller and strips protect the scope.

 

Not my idea btw, I kinda stole it from Trevor Jones of Astrobackyard.

 

At the end of the night, most of my stuff gets packed into the same container for storage until the next outing.



#5 petert913

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Posted 24 January 2020 - 10:51 AM

I wonder if there are any dummy USB plugs available to put in the slots when not in use?

 

Yep -->  found some:   https://tinyurl.com/u3ketrj


Edited by petert913, 24 January 2020 - 10:53 AM.


#6 Fukinagashi

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Posted 24 January 2020 - 10:54 AM

Yes there are rubber plugs on the market but I need something to protect the connections during the campaigns...

 

I wonder if there are any dummy USB plugs available to put in the slots when not in use?



#7 StrStrck

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Posted 24 January 2020 - 10:55 AM

If the mini-pc is oriented with it’s usb-ports upwards, condensation may run down the cable/plug into the port. 

Try rotating it, making the plugs and wires point downwards.



#8 Fukinagashi

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Posted 24 January 2020 - 11:08 AM

2 ports on one side and 2 ports rotated at 90 degree. Moreover it depends on where the scope is pointing.

 

 

If the mini-pc is oriented with it’s usb-ports upwards, condensation may run down the cable/plug into the port. 

Try rotating it, making the plugs and wires point downwards.



#9 StrStrck

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Posted 24 January 2020 - 11:39 AM

2 ports on one side and 2 ports rotated at 90 degree. Moreover it depends on where the scope is pointing.

Upwards...?!grin.gif

 

K, joke aside. Cut some 4 cm wide strips from a towel, and wrap around the plugs. See how wet they get, and does the short out coincide with very wet towel strips?



#10 jaythespacehound

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Posted 24 January 2020 - 11:45 AM

I have in the past cut the fingers off rubber gloves and attached those to the usb cable just below the usb connector with a rubber band.
Won't stop the condensation but will stop it running into the port down the cable...
Now that I've written that it does sound a bit crazy though :p


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#11 NearVision

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Posted 24 January 2020 - 12:18 PM

how would a plastic bowl/storage container work as a dew cover? Something slightly larger than the pc with cables attached that would sit on top with room around on all side and top for air to circulate. It would act like an umbrella so the only condensation worry would be any that collected on the inside of it. But I think inside condensation would be mitigated by the heat generated by the pc. The container would need to be large enough to allow for sufficient air circulation for pc cooling of course.


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#12 OldManSky

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Posted 24 January 2020 - 01:51 PM

how would a plastic bowl/storage container work as a dew cover? Something slightly larger than the pc with cables attached that would sit on top with room around on all side and top for air to circulate. It would act like an umbrella so the only condensation worry would be any that collected on the inside of it. But I think inside condensation would be mitigated by the heat generated by the pc. The container would need to be large enough to allow for sufficient air circulation for pc cooling of course.

I did something like that previously for my powered USB hub.  The 1/2 sandwich containers were just the right size.  Hub goes inside, slits cut in the sides to slip the USB cables through.  The powered hub itself generates enough heat to keep the inside toasty and prevent the outside from dewing.  I imagine a good-sized container for the mini-PC could be found to do the same thing...



#13 evansg

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Posted 25 January 2020 - 08:02 AM

The main problem of all commercial USB Hubs is the temperature range that electronics were selected and were certified to operate.

Nearly all of these USB Hubs were designed to work inside our cosy warm room. Commercial manufacturers never considered or cared that we use them for astronomy and they had to work outside in the harsh environment at low temperatures.

If you check the USB specifications of all of these hubs (from the cheapest you can find to the industrial HUBs like StarTech) you will see clearly that Operating Temperature is  0°C to 55°C (32°F to 131°F).

 

Here is an example: https://www.startech...Hub~ST4200USBM 

 

High humidity also affects the USB connectors but the most important problem here is the temperature range. We operate these HUBs out of specs! Nobody will ever invest and design - in large production scale - an automotive temperature range hub for commercial usage. Cost of the USB electronics is about 10 times more. Unfortunately this is the sad true..

This is actually the main reason why you get all of these disconnects during a cold night.


Edited by evansg, 25 January 2020 - 08:07 AM.


#14 Steve Cox

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Posted 25 January 2020 - 08:23 AM

If you're not unplugging the cables why not try silicone around the cable-port junction to seal them?


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#15 Brian K.

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Posted 25 January 2020 - 08:55 AM

I saw this on YouTube when looking for info on my CEM60. Exactly what you are talking about.

 

https://youtu.be/4xRBBuo6Kpo

 

Brian


Edited by Brian K., 25 January 2020 - 08:56 AM.

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#16 mclewis1

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Posted 25 January 2020 - 11:32 AM

Consider using some dielectric grease (it's a silicone based product and it comes under a variety of brand names) on the USB cable contacts. When I was using my scope in the backyard and when I first setup my observatory I was plagued by intermittent USB connections. After using the grease for a few years I've had solid electrical connections.

 

You need to be careful with the application of this product as it will hold debris. If for example you drop a cable into the grass you should carefully wipe the outer connector (and check that there's nothing obvious on the inner part) before you use the cable. So apply it sparingly and keep your cables ends clean and out of the grass.

 

The grease is hydrophobic (it sheds moisture), keeps electrical contacts from corroding and is not conductive. In Canada one popular source is - https://www.canadian...g-0383747p.html In Europe I'm sure there are other brands readily available, one good source are automotive repair/supply outlets.

 

In addition to help make USB cabling more reliable pay close attention to strain relief wherever possible, don't load cables (remove any weight pulling on a cable), and use good quality cables (better casings are more flexible which puts less strain on the connectors, and look for substantial gold contact areas).  


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#17 SonnyE

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Posted 25 January 2020 - 07:42 PM

There is no end to plastic bags you can use to encapsulate or tent over things to dew-proof them.

When using my DSLR for overnight image collections for time lapse, I take a 1 gallon Ziploc brand bag and cut one corner off.

Then poked my lens just through the hole in the corner and used the bag over my entire camera. Including my dew heater strip.

Dew Proof!

 

Cut a 1 quart or a 1 gallon bag half way up the side, and use it as a tent over your micro computer.

Dew Proof!

 

I gave up on messing with my NUC. It was just too marginal on it's ability to WiFi to my indoor computer.

And without a screen at the mount, I was literally wearing a path from my desk to the outside equipment during alignments.

So I went back to using a little Dell (brand) 2 in 1 Laptop/Tablet.

So much easier! And it reliably WiFi's inside to outside.

I use a plastic storage container laid on its side as an enclosure to shield my computer from any dew.

Dew Proof!


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