Author Topic: Mk III-LR humidity sensor issues - SOLVED!  (Read 311 times)

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Offline GrandLakeWX

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Mk III-LR humidity sensor issues - SOLVED!
« on: March 27, 2020, 10:04:27 PM »
Looking for some help diagnosing a problem with my Mk III-LR setup.  I have an CC-3000 inside feeding a Meteobridge that's linked to a Raspberry Pi running Home Weather Station.

I noticed the other day that it was dropping data, indoor and outdoor T & H readings were missing from my webpage (www.parusel.ca/pws).  When I looked at the system MB log, is says the inside and outside T&H data is bad and the humidity reading is out of range.  It's still receiving wind speed and direction though.

logger (27.03.2020 22:47:50): Bad thb0(0) sensor data, "humidity" (255) out of range [0:100]
logger (27.03.2020 22:47:50): Bad th0(0) sensor data, "humidity" (255) out of range [0:100]

When I hook up to CC3000 via the Rainwise Terminal program, this is what I get:

HDR,"TIMESTAMP","TEMP OUT","HUMIDITY","PRESSURE","WIND DIRECTION","WIND SPEED","WIND GUST","RAIN","STATION BATTERY","BATTERY BACKUP","TEMP IN",!E264
now
2001/05/01 02:59:54,  9.8,255,1002.3,202,  0.0,  0.9,  0.0, 6.96, 5.71, 27.1,!2C81

The humidity is definitely off the chart but the temp readings are ok.  Outside battery voltage looks good too (this reading was taken at 11pm).

So I guess what I'm wondering is if the outside humidity sensor is bad, why is taking out the indoor and outdoor temp sensor readings? Anyone ever run into this problem before?  Will changing out the sensor correct the problem?

Thanks in advance!
Paul


Ok, well I didn't want to but I retrieved the ISS from it's mount 45' up on a steep roof.  Upon opening it up, I noticed that there was condensation on the interior ceiling of the enclosure, not a lot enough to raise suspicion.  So I dismantled the guts of the ISS and checked everything out for obvious signs of damage/corrosion etc.  There wasn't anything obvious but when I unplugged the Zigbee module, it was apparent from the tarnished pins and white powdery sockets that it received a dose of water.  Using electrical spray cleaner, I blasted out the sockets and pins.  I applied a liberal coating of dielectric grease, pushing it into the socket holes and onto the pins and reinserted the module.  Unfortunately, this wasn't the problem, I didn't think it was, I was still receiving packets on the CC3000. I inspected the rest on the connectors on the main PCB but they all looked fine.  Next I pulled the anemometer out of the mast, along with the T/H sensor module.  The TH module was what I was suspecting the cause of the problems, but on inspection, there was no obvious issues.  For the heck of it, I pulled the anemometer fully apart and, cleaned and greased the bearings.  All looked fine, including the connectors which I had greased years before when I first put the station up.  I tested the outside temperature sensor with a DMM, it's just a NTC10K thermistor, it metered out fine and responded to temperature changes.

Hmmmm.  No smoking gun yet.  I plugged it all back together on the bench, however it still wasn't working but it did get one quick outside T/H reading.  That made me think the humidity sensor wasn't DOA after all.  So I carefully inspected the T/H sensor connector on the main PCB and found it had tarnish on some of the contacts.  Using a piece of abrasive rubber eraser, I carefully polished the contacts and sprayed them off with contact cleaner.  I cleaned the mating plug, plugged it back together and voila, it's working!

So, after all that, I cleaned all the connectors on the PCB, and then liberally greased them all with dielectric grease.  To prevent further problems with condensation drops landing on the connectors and causing corrosion, I slid an ESD safe ziplock bag down over top of the PCB to act like a raincoat.  Low tech, but I'm sure it'll do the job.  I also stuffed a small piece of filter material into the vent plug to keep the critters out.  I forgot to mention the family of spiders living in the ISS.  Greased the gaskets and enclosure screws, put it all together and we're off to the races. 

I would recommend to anyone with a Rainwise MKIII to watch for this problem, grease all of the connectors liberally and maybe try my raincoat idea if you have condensation issues too. 

Oh yes, and last thing I thought I'd mention is that when I reinstalled the ISS, I double checked the wind vane direction.  I recall in the manual that the PV panel was factory set to point south but when I aligned the vane to the PV panel and then checked the direction on my Meteobridge, I found it out by some 30 deg.  So I rotated the vane until my MB data said it was 180 deg S and the with a compass on the vane, or rotated the ISS until the compass indicated south.

Cheers,
Paul

« Last Edit: April 12, 2020, 07:33:11 AM by GrandLakeWX »

Offline looney2ns

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Re: Mk III-LR humidity sensor issues - SOLVED!
« Reply #1 on: June 22, 2020, 02:30:27 PM »
I use Caig's Deoxit, and it works wonders in cleaning up and preventing additional corrosion. Good stuff.
https://www.parts-express.com/Search.aspx?keyword=deoxit&sitesearch=true

Offline GrandLakeWX

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Re: Mk III-LR humidity sensor issues - SOLVED!
« Reply #2 on: June 22, 2020, 02:40:54 PM »
Thanks for the advice, might have to try a can.  Funny timing though, I actually had a re-occurrence of the problem, exact same symptoms.  Luckily I had ordered a spare connector jack to have on hand if the need arose, so I swapped it out and I'm up and running again.  I think once that atom-thick layer of gold is scuffed off the contacts, no matter how clean or greasy it is, it'll eventually fail. We'll see, it's day 3 and all's well ;)

Paul