Humidity issues

[adictoetico]

I have a teensy 4.1 that lives is a "weatherproof box" on a roof for an old Neon sign that I repurposed using LED strips....
the box is apparently not weatherproof as every time there's a heavy rain it fails and the sign stops turning on, after coming up to diagnose the problem I get to a dead board that is not turning on, after a cleanup and letting it dry, it comes back to life but its reverted to the blink code. I am suspecting moisture shorting out the pushbutton or something of the sort.

has anyone experienced similar issues?? I am trying to rule out any moisture getting in the box to really be sure its humidity that is getting in there, but would like to pick your brains for any experience with similar issues.

thanks

 

[dundakitty]

I've had similar problems, due more to power cycles than humidity. In my case they are teensy 3.6 processors that are indoors. I just had another teensy 3.6 lose programming, in a totally different project than the ones described
here.

 

[MAW2732]

All our PCBs over the last 40 years have been treated with a MIL-V-173 conformal coating varnish that holds up for years. Just completing a new design that uses the Teensy 4.1 instead of a simple uC and realized that the mother board it piggybacks onto will be treated in the same manner, but the Teensy itself will need a lot of attention to keep safe.

The application is in the marine environment, not directly exposed to any direct spray, but in a warm (up to 50C) engine room. The humidity will be high and will carry/deposit salts on the boards. After soldering the pins on the board the backside of the Teensy can be coated, then set aside to dry. The topside is a different story with the USB port, reset switch, and the SD Card connector. Aside from creating a "bubble" for the entire Teensy, any thoughts on how to protect it's connections and bits?

Thanks

 

[Angelo]

For the railway industry, I use a "breathing" device. It is like an M12 bolt, with integrated Goretex membrane. It let the ROSE enclosure breathe and expell humidity due to temperature changes.
And the pcb is also coated.

 

[MAW2732]

For the railway industry, I use a "breathing" device. It is like an M12 bolt, with integrated Goretex membrane. It let the ROSE enclosure breathe and expell humidity due to temperature changes.
And the pcb is also coated.

Thank you Angelo, I'll do a bit of reading this morning on that.

 

[MarkT]

Seriously consider a hermetic enclosure for the teensy in a marine environment, no connectors handle salty air well, unless you pot them and put them beyond use!

For everyday rain exposure the push button needs to be IP68 or similar I think, such as a "vandalproof" switch. And a small enclosure for the teensy with every cable entering from below may suffice - the heat generation will keep the board from condensation itself, and some external insulation on the enclosure is probably needed to stop condensation in it at night.

However hermetic sealing will be better.

 

[mborgerson]

Seriously consider a hermetic enclosure for the teensy in a marine environment, no connectors handle salty air well, unless you pot them and put them beyond use!

For everyday rain exposure the push button needs to be IP68 or similar I think, such as a "vandalproof" switch. And a small enclosure for the teensy with every cable entering from below may suffice - the heat generation will keep the board from condensation itself, and some external insulation on the enclosure is probably needed to stop condensation in it at night.

However hermetic sealing will be better.

There are plenty of connectors that not only handle salty air, but seawater immersion to hundreds of meter depth. I've designed loggers using them for more than 40 years. The type with which I'm most familiar is the SEACON All-Wet line.

SEACON Connectors

We often used a 2-pin connector as a power switch for the batteries and a 4-pin connector for USB access to the logger. The latter allowed us to upload the data without opening the pressure case. Once you've assembled, tested, and calibrated an instrument, you do a pressure test to make sure it won't leak at 200 meters depth. Once it has tested good, you should do another pressure test every time the case is opened.

Be prepared for sticker shock if you decide to use connectors like these. A set for one instrument was over $1000 when I was last involved in purchasing a few decades ago. I'm pretty sure that there are waterproof connectors good at one atmosphere pressure for a lot less. Marine supply houses are a good place to start looking.