How to expose a BME280 to pressure/humidity outdoors w/out [long term] damage?

Experts,
I am making an outdoor weather sensor from a BME280 (for this question, does it matter?). Just as I was about to buy a completely water-/air-tight container for it to live in, I realized doing so would deprive it of at least humidity, and probably pressure from outside the container.

I looked at the little board and thought, "I'll seal it with ____!". But that would make things worse. I guess you could say that even having the temp sensor inside the box-especially if there is sunlight, would make it inaccurate as well. And covers like these, even though they lure me in with "Fine and elegant workmanship", still give me suspicions...

So how would you expose a sensor [board] to the elements without all the Bad(TM) things in the elements corroding/damaging the board? With a humidity sensor, is it unavoidable?

TIA!

Weather sensors are normally mounted in wooden enclosures with open vented slatted sides. This lets in pressure and temperature changes whilst keeping rain off, otherwise known as a Stevenson screen. Here's a set of building instructions :-

Your link does not work. Please fix that because I have been looking to purchase something like that and have not been successful!

My weather station uses an ams2320b temp/humid sensor, which comes in a similar case. I mounted it in a position open to the elements but shielded from direct sunlight. The first one lasted a little over a year before it developed a fault causing it to permanently read 100% RH. I will let you know how long the replacement lasts! I dismantled the faulty sensor but could not see any visible damage. I kept the plastic case with the idea of putting a bme280 inside.

First minimise the amount of electronics that has to be out in the elements. Just the BME280 and the minimum support components required to transmit the data to the indoor unit.

Then design the box so that all cable entries are on the bottom and nothing can wick in along a cable or mounting screw. Water can travel uphill if you give it a good capillary tube. There's lots of clever ways to build Stevenson screens. My favourite is the stack of white plastic plates on threaded rod. Cut the center out of most of the plates except for 2 on top and 1 on the botttom. Plastic cups would work well too.

Finally coat the entire PCB in conformal coating. I only purchased this once in an electronics store and then I realized that it smelled exactly like ladies' nail polish. Buy clear nail polish - any brand name is OK - and paint all of the board except for the sensor hole on the top of the BME280. Put extra coats over any sharp points like the soldered tips of the incoming wires.

jackrae,
Thanks for writing! I have thought of 'something with holes', and I thought perhaps that might invite unwanted visitors. I live in New England, so we get highs and lows, and I was thinking maybe bugs would be an issue... Probably not if I use some kind of tight mesh screening-the kind they use in Florida for the 'no see ums'... If nylon, no rust...

I think I have a good place facing North in the shade, and maybe if just the chip (coated as @MorganS mentioned), no problems... I know it seems a silly, small thing, but... :slight_smile:

I think I'll go by my Home Depot here and grab a small amount of nylon 'screening', as they all look at me funny! :slight_smile:

jackrae:
Weather sensors are normally mounted in wooden enclosures with open vented slatted sides. This lets in pressure and temperature changes whilst keeping rain off, otherwise known as a Stevenson screen. Here's a set of building instructions :-
http://www.instructables.com/id/Stevenson-Screen-weather-station/

@MorganS,
Thanks for writing!

This is such a great idea!

Thanks!

MorganS:
First minimise the amount of electronics that has to be out in the elements. Just the BME280 and the minimum support components required to transmit the data to the indoor unit.

Then design the box so that all cable entries are on the bottom and nothing can wick in along a cable or mounting screw. Water can travel uphill if you give it a good capillary tube. There's lots of clever ways to build Stevenson screens. My favourite is the stack of white plastic plates on threaded rod. Cut the center out of most of the plates except for 2 on top and 1 on the botttom. Plastic cups would work well too.

Finally coat the entire PCB in conformal coating. I only purchased this once in an electronics store and then I realized that it smelled exactly like ladies' nail polish. Buy clear nail polish - any brand name is OK - and paint all of the board except for the sensor hole on the top of the BME280. Put extra coats over any sharp points like the soldered tips of the incoming wires.

I used one of these from Amazon for my hive monitor system. It houses a HTU21.

Very good although it does give a raised temperature when in full sun but this is apparently a problem for all types of housing

Temperature/Humidity Housing

@MarkDerbyshire,

I have a handful of those transmitter (systems)! I always need to put them in shady spots! The reason for my obvious posts about a self-powered weather node is because of these. The batteries go way too fast! That, and the fat that they are stand-alone (you can't plot/store output).

I have one that has an anemometer on top of it, and I have to somehow figure out how to hack it so I can use the anemometer as an input to my remote weather node! :slight_smile:

What a coincidence!

Thanks!

@holesflow, did you check out my link? The battery in my weather station lasts around 12 weeks.