Author Topic: WS2812 outdoor humidity reads single-digits in fog  (Read 368 times)

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Offline icebound

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WS2812 outdoor humidity reads single-digits in fog
« on: June 27, 2017, 10:18:02 AM »
A few months ago, my WS2812 (with the TX59UN-1-IT sensor) began acting weird.

I noticed that, when we had fog or rain situations, the humidity would read very low...like in the teens.

I reviewed several months of stored data (hourly), and found that below about 75% outdoor humidity... (checked against nearby airport reports)... my sensor seems to be "close enough".  This included the "actual" dry conditions, where the real humidity was down in the 30s.  (we rarely go below 30 around here).

But once the real humidity gets higher than 75 or thereabouts, my READINGS plummet into the 30s.  As the humidity gets higher, the readings get lower: 20s, teens.  In one dense fog situation where the airport said 98% (as expected), my reading was 8%. That's EIGHT.

It is almost as if the reading is:... 100 MINUS "actual-humidity".


Does anybody have the engineering explanation as to how the sensor can read "dry" in both "actual dry", and "actual wet" situations?

...And, of course, do you think there is any potential fix, (beyond the obvious, of replacement)?  (And yes, clean the cobwebs, new batteries, etc.)

...

Offline weatherist34

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #1 on: June 27, 2017, 10:55:12 AM »
A few months ago, my WS2812 (with the TX59UN-1-IT sensor) began acting weird.

I noticed that, when we had fog or rain situations, the humidity would read very low...like in the teens.

I reviewed several months of stored data (hourly), and found that below about 75% outdoor humidity... (checked against nearby airport reports)... my sensor seems to be "close enough".  This included the "actual" dry conditions, where the real humidity was down in the 30s.  (we rarely go below 30 around here).

But once the real humidity gets higher than 75 or thereabouts, my READINGS plummet into the 30s.  As the humidity gets higher, the readings get lower: 20s, teens.  In one dense fog situation where the airport said 98% (as expected), my reading was 8%. That's EIGHT.

It is almost as if the reading is:... 100 MINUS "actual-humidity".


Does anybody have the engineering explanation as to how the sensor can read "dry" in both "actual dry", and "actual wet" situations?

...And, of course, do you think there is any potential fix, (beyond the obvious, of replacement)?  (And yes, clean the cobwebs, new batteries, etc.)

...

hello

probably what is happening the circuitry is exposed to the build up of dew or condensation causing the readings to go awol and erratic you basically end up with a short circuit until it dries out . water , residue,dew  are all conductors..

i live by the sea aprox 150m away on my ws1001 model when i first installed it two years ago i had similar issues during fog,rain etc so I opened it up and addressed
the areas that were looking prone to becoming a short circuit due to build of of condensation or dew .i simply also sealed any opening areas with silicon grease apart from the downward vented airflow areas . also applied a thin non conductive layer of grease to the circuit board where the sensors mounted on.

i don't know the insides of your model but i suspect this is the case . if you can find any photographs or images of the inside circuitry or component layout i could pinpoint to you how to address.its not that difficult if you have a steady hand and a bit of patience .

dew,dense fog can play havoc with most outdoor electrical components that are NOT well protected, you would think a weather station component would be up to standard unfortunately many are not .

i first learnt about dense fog playing havoc with components some 30 years ago building amateur radio antennas the dense fog would find its way to the cheap coaxial connectors i used , so therefore all my tuning readings were erratic ! .

also poorly installed satellite tv antennas are prone to this again the dew or dense fog just finds its way in to create a short circuit ..

brian

as i said above if you can find an image of the inside not the shield itself as below



 
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Offline LeeWx

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #2 on: June 28, 2017, 01:44:41 AM »
Same thing happened to my Vantage Vue. It is gradually getting worse as when it first acted up it would reach about 86% humidity before dropping as actual humidity continued to rise. It now drops all the way to 36% when socked in with fog or 100% saturation.

Online DanS

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #3 on: June 28, 2017, 02:39:16 AM »
"as i said above if you can find an image of the inside not the shield itself ..."
I believe my TX59U-T is pretty close, if not the same, as yours. Believe it's just a firmware
difference.
 [ You are not allowed to view attachments ]
I had a Ws-2810 do the same thing years ago. The humidity sensing portion of the T/H sensor had what looked like cob webs inside. I finally ended up ordering a Sensirion SHT11 chip, cut the traces to the onboard sensor, and spliced in the SHT11.
« Last Edit: June 28, 2017, 02:43:45 AM by DanS »

Offline weatherist34

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #4 on: June 28, 2017, 03:21:40 AM »
"as i said above if you can find an image of the inside not the shield itself ..."
I believe my TX59U-T is pretty close, if not the same, as yours. Believe it's just a firmware
difference.
 [ You are not allowed to view attachments ]
I had a Ws-2810 do the same thing years ago. The humidity sensing portion of the T/H sensor had what looked like cob webs inside. I finally ended up ordering a Sensirion SHT11 chip, cut the traces to the onboard sensor, and spliced in the SHT11.

as i expected poorly isolated circuitry . lots of exposed solder points and bare copper points . not uncommon but begs the question is this mounted inside the radiation shield openly like this or is it in a isolated compartment. ?
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Online DanS

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #5 on: June 28, 2017, 04:20:02 AM »
There is a coating of something like clear shellac covering the traces, joints and pads. Had to scrape a little to take measurements.

Offline weatherist34

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #6 on: June 28, 2017, 04:29:48 AM »
There is a coating of something like clear shellac covering the traces, joints and pads. Had to scrape a little to take measurements.

thats just solder flux and thin uv resist ink look at the exposed components you only need one component to become erratic due to dew,condensation etc and that will affect others.

how is the circuit board mounted inside the shield ?
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Offline icebound

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #7 on: June 29, 2017, 04:54:52 PM »
This is a picture of the board.

The temp humidity sensor appears to be the unit in the middle of the board.
the traces have been definitely painted over with a clear something.
 [ You are not allowed to view attachments ]

The board is mounted completely inside a case which a few air-slots cut. [ You are not allowed to view attachments ]

The whole thing then slides into the radiation shield  [ You are not allowed to view attachments ]

Offline weatherist34

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #8 on: July 01, 2017, 07:12:09 AM »
hello

if i had that board in my hands i would basically be looking to isolate those exposed components . the sensor itself looks protected but it is the circuitry that is causing the erratic readings.
self-amalgamating-tape is very effective

self amalgamating tape self bonding rubber and silicone tape excellent  for moisture resistant electrical insulation

http://solutions.3m.co.uk/wps/portal/3M/en_GB/ElectricalMkts/ElectricalSupplies/products/electrical-tapes/self-amalgamating-tape/

this is not a perfect tidy clean solution but then we dont need to look at it as it is hidden once mounted inside.



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Offline dupreezd

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #9 on: July 01, 2017, 07:46:05 AM »
Look up Conformal Coating. It is available in spray and paint on. It is not cheap   :-( , but a little bit goes a long way. It also contains a UV reflector to allow inspection of boards to check for uniform coverage.

It has been used for years to protect electronic circuit boards.
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Offline icebound

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Re: WS2812 outdoor humidity reads single-digits in fog
« Reply #10 on: July 12, 2017, 10:09:13 PM »
Just to update...
I tried automotive ignition protector.  Goes on clear. Basically painted the whole board except for the insides of that  sensor.

No real change.  No damage, but no change.

Eventually gave up and got a complete new temp/rh unit;

works fine.

...