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Topic # 201286 11-Aug-2016 21:58
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After my cheap Dick Smith Tesa WS1151 weather station threw a fit leading me to think it was broken, I've been looking into software defined radio USB dongles and decoding the signal from the sensor outside.

 

I ended up buying the nooelec smart USB dongle, which came with 3 aerials.  Tonight I loaded up some SDR software and completely failed to work out how to see the signal at 433Mhz in them - it just looked like a waterfall of white noise.  So I took a look at the open source rtl_433 tool which has dozens of protocols for different weather sensors already.  Someone has kindly set up a daily build for Windows, saving me the trouble of building it and it's dependencies.

 

Running rtl_433 in blind scan mode where it tries out all the known protocols, and eventually I saw this:

 

2016-08-11 21:47:03 : Fine Offset Electronics, WH2 Temperature/Humidity sensor
ID: 195
Temperature: 3.8 C
Humidity: 52 %

 

Bingo, that matches the readout on the limited overly complicated display sitting on the bench.  And leads to this protocol implementation.  In theory, I could buy a few more sensors and plant them around the place and this tool would I guess spit out all the different readings for all the different sensors with their random ids.  I could probably buy a cheap wireless rainfall/wind thing and it would pick that up as well.

 

I imagine the next step will be looking into raspberry pi development so I don't have to have it hooked up to my laptop, and I can have a log of the temperatures and graph them and all sorts of similar things.  Anyone played with this sort of cheap home-brewed set up?


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  Reply # 1610370 11-Aug-2016 22:30
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Hmmm... You've got me thinking now...I have a bunnings "Holman" wireless weather station. It has rain, wind (speed and direction), temp, humidity ... I might have to look into something for my laptop.


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  Reply # 1610381 11-Aug-2016 23:19
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Must give this a go. I think the station outside is still broadcasting even tho the inside part will not sync with it.





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  Reply # 1610397 12-Aug-2016 00:33
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OK, its working for the weather station, which is actually inside because I took it down when I was taking down the rattling VHF antenna sometime last year.

 

It gets the WH2 sensor for my outdoor temperature/humidity display.

 

Doesnt seem to show any of the 6 fine offset WH3 sensors which are just temperature however.

 

Now to see if I can get a pi doing it and then doing something useful with the output.





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  Reply # 1610467 12-Aug-2016 09:12
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richms:

 

OK, its working for the weather station, which is actually inside because I took it down when I was taking down the rattling VHF antenna sometime last year.

 

It gets the WH2 sensor for my outdoor temperature/humidity display.

 

Doesnt seem to show any of the 6 fine offset WH3 sensors which are just temperature however.

 

Now to see if I can get a pi doing it and then doing something useful with the output.

 

 

Where did you get the WH3 sensors from?  From what I understand these should show 0xFF in the signal for the humidity, and be picked up by the same algorithm.


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  Reply # 1610636 12-Aug-2016 12:22
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eBay. One of them comes up as some other brand temperature sensor but the rest are not.

I got part way thru a decoder in arduino but it was too unreliable with the crap cheap OOK 433mhz module I had which just constantly output noise. And putting a rfm12 (from memory) on a pi was even worse.




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  Reply # 1610659 12-Aug-2016 12:43
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Thanks for this, the outdoor part of my weather station is fine but the base station locks up about once a week (a known issue with my model). I've played with cheap 433Mhz receivers before and never had much success, this looks promising.


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  Reply # 1610682 12-Aug-2016 12:58
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I'm planning on using a Wemos D1 mini (ESP8266-based device) to run my weather station (the up-the-pole electronics died a while ago). If the ESP8266 isn't up to it, maybe some other Arduino with a Wifi shield. Or a Raspberry Pi.

 

Whatever, I'll use WiFi to send the data to my desktop, or a NAS, or whatever... no need for that base station, nor the unreliable 433MHz link. 

 

 


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  Reply # 1610685 12-Aug-2016 13:13
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I am using a Moteino as my DIY weather station. They are relatively cheap (around $US20) and Arduino compatible. They are designed to operate in low-power modes so perfect for battery driven projects. I have one Moteino out in the garden with a DHT22 + BMP180 + a rain tipper (from an old WS-1080) and then another inside wired up to an ethernet connected Arduino acting as the RF gateway. I have a cheap solar panel and little LiPo battery and this is enough to power the station without ever needing to recharge the batteries.

 

You might find that LiPo + solar will be enough to run a Wemos D1 mini as well? 




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  Reply # 1610693 12-Aug-2016 13:36
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If you've got a device it doesn't recognise, rtl_433 also intercepts the raw data and prints it as a bit string.

 

When I restrict it to only parsing a device I don't own, it sits there and detects and outputs the following:

 

Detected OOK package
Analyzing pulses...
Total count: 48, width: 24406 (97.6 ms)
Pulse width distribution:
[ 0] count: 22, width: 127 [126;130] ( 508 us)
[ 1] count: 26, width: 371 [370;374] (1484 us)
Gap width distribution:
[ 0] count: 47, width: 253 [252;256] (1012 us)
Pulse period distribution:
[ 0] count: 22, width: 381 [380;384] (1524 us)
[ 1] count: 25, width: 625 [623;627] (2500 us)
Level estimates [high, low]: 15922, 214
Frequency offsets [F1, F2]: 19732, 0 (+75.3 kHz, +0.0 kHz)
Guessing modulation: Pulse Width Modulation with fixed gap
Attempting demodulation... short_limit: 249, long_limit: 257, reset_limit: 257, demod_arg: 0
pulse_demod_pwm(): Analyzer Device
bitbuffer:: Number of rows: 1
[00] {48} ff 4c 30 91 24 d4 : 11111111 01001100 00110000 10010001 00100100 11010100

 

And this is the pretty much the packed data for preamble, type, random id, temperature, humidity, crc, for the WH2.  It also detects my car key, but that's a rolling code, so randomesque.


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  Reply # 1611398 14-Aug-2016 15:47
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rmt38:

 

 

 

.....

 

I imagine the next step will be looking into raspberry pi development so I don't have to have it hooked up to my laptop, and I can have a log of the temperatures and graph them and all sorts of similar things.  Anyone played with this sort of cheap home-brewed set up?

 

...

 

 

I wouldn't know where to start myself, but reading your posts I would expect you're clever enough to be able to interface (write a driver??) it to WeeWX.  That would mean all the heavy lifting on archiving, databases, graphing, etc. is already done for you.





Most of the trouble in the world is caused by people wanting to be important. (T.S. Eliot)




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  Reply # 1611845 15-Aug-2016 11:36
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I also bought a cheap $9 USD SDR receiver, which finally arrived this morning.  It doesn't do too badly even with it's smaller aerial, it picks up the same FM stations vaguely.  And it easily picks up the fine offset weather readings with rtl_433.exe.

 

If anyone is thinking of buying one and doesn't want to spring for one of the better models as they'll only be reading 433MHz device signals, one of these would likely be fine.  It was noticeably warmer than the cold nooelec model which I think has passive cooling, but I think that's a known issue with the cheaper models along with other things.


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  Reply # 1611851 15-Aug-2016 11:41
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I have had the tuner die after a few months on all the cheapies I got in one lot of them. Once dead they will claim to be tuning ok but nothing happens.





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  Reply # 1611863 15-Aug-2016 11:53
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rmt38:

I also bought a cheap $9 USD SDR receiver, which finally arrived this morning.  It doesn't do too badly even with it's smaller aerial, it picks up the same FM stations vaguely.  And it easily picks up the fine offset weather readings with rtl_433.exe.




Same as the one I ordered off eBay the other day.



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  Reply # 1612639 16-Aug-2016 18:33
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This is another one which I'd consider buying as a low cost, reliable option at $25USD with free international shipping and antennas.  What I like about them is the open way they release new models with tweaks.


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  Reply # 1612666 16-Aug-2016 19:23
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I might grab a couple of the metal fancy ones, since I think that the problems I had in the past were overheating related causing the tuner to die.

 

In anycase, tuning them to 315000000 also gets the little keychain remotes I got for some other purpose appearing in there as well, which is great.

 

Has anyone found any details of getting this running on a pi or something and sending the data to something useful? If I could get cheap 315MHz aliexpress motion sensors being recieved it would be a good alternative to the ugly bulky wemo ones I have at the moment.





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