Protecting arduino from humidity

Hello. Since all the hardware connections are made by input/output pins on arduino, and all the electronical component on the arduino platform is exposed to the air, they must be very weak to humidity. What is the best way to protect arduino from humidity? Also, is there any normal operation temperature range for arduino?

What kind of humidity are we talking about? Like, expressed in % relative humidity, it may help to know how high exactly you had in mind.

i don't know much percentage of moisture content in the air can damage arduino. What can be the best way to protect arduino from wet condition?

I would encase everything in a wax molding. This would of course require things like an external reset. But what you could do is place your humidity-sensitive electronics in a project box with one side missing, route all needed wires to outside the box, then pour hot liquid candlewax into the enclosure, covering everything, then letting the wax dry.

This is just a suggestion, I've done this before but you should consider that once it is enclosed you will not be able to add new wires or replace the microcontroller if you need to.

HTH

You can always put it in a plastic box with some packs of silica gel in it. If you have to run wires into the box, make a hole and seal it with silicone caulk

Thank you. Do you have some picture examples of such arduino protection using plastic box with packs of silica gel? I wonder how much packs of silica gel are required to fully protect arduino and also how long does it last.

This is just a suggestion, I’ve done this before but you should consider that once it is enclosed you will not be able to add new wires or replace the microcontroller if you need to.

Well you could if you really wanted to.
Just gets a bit messy. ;D

Most things I’ve seen with sillica gel only have one small pack.
Its pretty effective stuff. You dont need a lot of it.

Plus the microcontroller should be pretty humidity resistant by its self.
They arent very fragile.

I see. What about the input/output pins of arduino? Are they humidity resistant, too? I thought they were very weak to wet condition and if they are exposed under heavy humidity condition, they could creat bad things to the performance of arduino.

It depends what your doing I suppose.

If your making something for a greenhouse or similar then I'd just throw it in a box to protect it.

Have you considered, keeping the arduino in a lower-humidity environment and running wire to your sensor(s) inside the high-humidity? I'm not sure if this applies to your case but I've had a similar issue. In my greenhouse controller, the controller box with outlets & an arduino, were placed outside the greenhouse, and sensors on a cable were run to the inside to monitor the readings.

I think it can be a good solution. I have a sample of PCB which is covered with rubber material. This rubber material is sealing every part of PCB while all the input/output pins are guided to the bottom and connected by water proof socket. But, I don't have a picture now. I will take a picture and post it soon.

Through below link, you can see a picture of PCB that is totally sealed by rubber.
Imgur

"Conformal coating"

Conformal coating is reasonably easy.

Degrease using a degreaser http://www.mgchemicals.com/products/411.html

Use masking tape to mask off connectors and buttons, socketed parts or components that will move, or get hot enough to exceed the rating of the coating (which is high at 149F).

Note: be sure to mask off parts all the way to the board, this cc will wick up into connectors and buttons ruining them. Yes have scissors and patience as you'll be cutting tiny pieces to seal up odd areas. It's most important to mask solder connections if you have to make a choice. If you can't get coating somewhere spray some in an aluminum foil cup and use a brush, make the cup out of foil or pay big bucks for lab dishes. ;) It's messy and you'll glow in UV light.

http://www.mgchemicals.com/products/419b.html

Use a UV light to make sure you got every place needed. Make sure it cures 24 hours before testing the unit as while wet the conformal coat will effect analog inputs. You should check your analog calibrations and compensate for any drift which should be minimal.

There are other coatings which increase in cost and difficulty in application but are not usually hobby friendly.

The barebones board is probably easier to coat. I don't recommend coating a socketed part but you can mask it off and leave it masked under the conformal coating. That makes it possible to replace the chip if needed. http://moderndevice.com/index.shtml

Connections to the board should have some protection but it should be removable. Simple electrical tape is messy but cheap. You can use an RTV compound but it's hard to remove. We don't worry about in out product as the pins are gold plated and hold up well except for full submersion which we don't warrant. ;)

I've probably missed something but I'm sure someone else has more info. That chemical company has an application guide. I've used their stuff it's good but there are others out there that meet the specifications they have. Choose based on how well a company informs you, treats you and price. ;)

Thank very much for your detailed advise. I will try just like that.