cloudy cloudy

Author Topic: Oregon WMR300 (and possibly Davis) Humidity Sensor  (Read 683 times)

0 Members and 1 Guest are viewing this topic.

Offline AlanB

  • Commercial
  • Posts: 131
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 70.0.3538.110
Oregon WMR300 (and possibly Davis) Humidity Sensor
« on: December 17, 2018, 05:43:52 PM »
Hi All
I am now on my second WMR300 temp/humidity sensor which is failing (stuck on mid 90% RH). I understand the Davis, possibly only earlier ones, has had similar. Has anybody tried changing the SHT11 sensor to the SHT21 on a breakout board. The advertising suggests it is a replacement so I thought I would give it a go but I don't expect delivery until January. SHT11's are available but, surface mounted, very fiddly to replace and maybe still unreliable.
Regards
Alan

Offline niko

  • syzygy
  • Global Moderator
  • Posts: 28,040
  • Crystal Ball broken! Please post the URL.
  • Northern California, U.S.A.
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #1 on: December 17, 2018, 05:58:58 PM »
Based on my reading of the data sheets the SHT-11 and the SHT-21 have different interfaces. For the earlier products (SHT-1x) Sensiron used their own Sensibus (?) interface, but for later products (SHT-2x, SHT-3x) they used standard I2C. You might look at the SHT-75 which I understand is a mounted version of the SHT-11 but please read the data sheets very carefully.

Offline niko

  • syzygy
  • Global Moderator
  • Posts: 28,040
  • Crystal Ball broken! Please post the URL.
  • Northern California, U.S.A.
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #2 on: December 18, 2018, 01:15:52 AM »
I should add that something potentially confusing is that Davis switched from the SHT-11 to the SHT-31 BUT it is a custom/special order version of the SHT-31 which has the old Sensibus interface rather than the now standard I2C interface. The standard SHT-31 that's available from electronic parts distributors and assembled on boards on ebay will not work with a Davis station.

Offline AlanB

  • Commercial
  • Posts: 131
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #3 on: December 18, 2018, 10:05:40 AM »
Thanks for that - with the 12c interface I can possibly use it as a spare for the Luftdaten so all of 8gbp is not lost.
I think Brian was looking at using the Luftdaten temp/humidity as an option so that would solve the problem.
I tried removing the potting on the previous defunct board but it destroyed a surface mount resistor so repairs are not easy.
Anyway many thanks Niko
Alan

Offline Ralph1

  • Posts: 132
  • Auchterhouse, Angus, Scotland, UK
  • OS/Browser:
  • (Linux Mint)
  • Firefox 64.0
    • Auchterhouse Weather
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #4 on: December 18, 2018, 03:02:17 PM »
Has anyone tried to use the Sensirion SHT31-ARP which has analogue outputs from the chip directly?  This would make a very much simpler way of getting temperature and humidity readings.  I use a Labjack U3-LV on my station which accepts analogue signals very easily. It seems to me that using the SHT31-DIS (the digital version) requires a RaspberryPi or Arduino to access the 12C address system. Perhaps there is a solution using the Labjack to interface the digital version directly, but if there is, I'm not aware of it.

It's a pity all these devices are so small, assuming you can get a suitable mounting board, it is very difficult to solder them in, requiring very small solder bits and steady hands, neither of which I have. I guess they are designed for production, and not for the DIY market.

Offline niko

  • syzygy
  • Global Moderator
  • Posts: 28,040
  • Crystal Ball broken! Please post the URL.
  • Northern California, U.S.A.
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #5 on: December 18, 2018, 03:23:30 PM »
I have never used the analog version but it should work and is available from distributors here.

I have used the I2C SHT-31 with very cheap (few $) picaxe and micromite processors to get an RS-232 serial output. The regular SHT-31 is available mounted on a board from many ebay sellers for a few $. It would not take much additional work to also generate an analog voltage output from that sensor/chip combination.

Offline Weather Display

  • Posts: 86,888
  • Davis VP2
  • New Zealand
  • OS/Browser:
  • Win NT 10.0
  • Chrome 70.0.3538.110
    • Weather Display
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #6 on: December 19, 2018, 01:34:30 AM »
Quote
I think Brian was looking at using the Luftdaten temp/humidity as an option so that would solve the problem.
i did
and posted about that
but never heard back from anyone

Offline AlanB

  • Commercial
  • Posts: 131
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #7 on: December 19, 2018, 10:05:42 AM »
Hi Brian
Sorry - I missed that. I have put what I found in the Luftdaten thread.
Alan

Offline AlanB

  • Commercial
  • Posts: 131
  • OS/Browser:
  • Win 7/Srvr 2008R2
  • Chrome 71.0.3578.98
Re: Oregon WMR300 (and possibly Davis) Humidity Sensor
« Reply #8 on: December 19, 2018, 12:55:52 PM »
Hi
I found a SHT31-arp on a breakout board so we will see - the V+ & GND are easy to work out but the T & H might be guesswork.
Regards
Alan