Measuring empy space

If you've been following my recent posts on twitter, you'll be aware that I've finally got round to hooking up the MaxBotix rangefinders into our water tanks. So far I've done the main house tank and have sketches and buried duct ready to do the ones that water the garden.

Some more technical details here than I can fit in tweets:
* The sensors themselves sit through the roof of the tank. This involves drilling a 3/4" hole in the top of the tank and inserting the sensor from below, so you won't want to put it more than an arms reach from the access hole. The sensors I purchased have NPR thereads not BSP, so you may want to pick up matching nuts at the same time depending on local availability.
* I mounted some 6-way header pins on the sensor, and soldered the female end onto the cable so that it didn't twist as I tightened it up. All mounted in a 20mm conduit box on the tank.

Inside the shed, I'm just using a clone arduino with a wiznet ethernet shield (ebay/aliexpress) and a very basic sketch using the pulse width measurement from the sensor. As normal, it's available on GitHub for anyone interested. It pushes to an on-site MQTT broker (mosquitto) that's used to gather various sensor metrics and fed into home-assistant, where it also gets archived into InfluxDB for longer term plots

status/housetanksensor online

sensors/housetanks/depthbelowsensor 419

sensors/housetanks/litres 20762

I use the status for LWT messages, and the sensors has the raw air-gap measurement (mm below sensor - range is 300 -> 5000) as well as a calculated volume (see the arduino code for constants and calculation)

Importing into hass is as simple as

  - platform: mqtt

    name: House water tanks volume

    icon: mdi:water-pump

    availability_topic: status/housetanksensor

    unit_of_measurement: l

    state_topic: sensors/housetanks/litres

into the configuration.yaml

Next up, getting the irrigation system working...

Publishing DHT22 data via MQTT with an ESP8266

Some time ago I picked up a couple of ESP-01 modules with the intention of using them as wireless temperature/humidity sensors coupled with a DHT22.

Initial investigations took place at the Perth Artifactory "Arduino-U" evenings - I managed to put on a nodemcu lua firmware and found a few (varying) dht22 libraries. however I couldn't ever manage to get it to consistently publish the information to my message broker - it'd do one or two and then lock up. I dug it out again recently and decided to have another go - especially as Pete Scargill seemed to be having success with them (running native C).

So trying to 'revert' to a newer espressif release turned out to be non-trivial - installing the relevant toolchain needs multiple bits. I gave up and noticed that there was a newer (0.9.6-dev_20150704) nodemcu release, so I gave that a try.

First discovery - There's native support for the dht sensors in the firmware, so to get the current values all you need is a

print(dht.read(4)) 

So, I trivially modified the example mqtt.client from the docs and uploaded it with luatool. I'd already set my wifi parameters by hand, so it was connecting to the network at power on automatically. Once I was happy that my 'pub.lua' was publishing OK, I added a trivial init.lua (also available on the gist)

Some points to note from that gist:

• IP address of broker is hard coded. The nodemcu example uses a non standard port - be aware if you copy n paste
• Although I have a last will, there's no status setting on successful connect. needs fixing.
• I'd rather have temp / humidity as two separate topics, but I merged them into one json string to avoid having to worry about mqtt publishing concurrently (used to be fragile on the esp8266)
• I publish every 5s (tmr.alarm) - 2s is the min recommended for the dht22

so I now see a pretty

sensors/ESP-10264640/json { "temp": 16.8, "humidity": 53.4 }

every 5 s ("mosquitto_sub -h broker -t '#' -v" makes for great sanity checking), which is great but not terribly pretty. Thankfully I have a websocket enabled mosquitto broker running, so I'd already dabbled at some html display. so I took jpmens' dial example and altered it to one of the other gauge styles. and lo...

Low-Level hardware hacking

In our 3 shiny new computer rooms (supercompute, IO, Tape - Each with slightly different environmental and cooling requirements), the architects have fitted a single temperature sensor on the back wall. Out of the airflow. This isn't giving us a terribly accurate picture of the supply air going into each rack, and so an alternative DIY method is underway.

A Raspberry Pi in each room (small, low enough power that it can be fed from PoE via a splitter) acts as the local 'head' and grabs the data to send it to a central message broker. From there, we can choose what to do and how to display it.

The sensor hardware consists of: A single DHT22 attached near to the Pi - As useful as these are on an arduino, on a R-Pi they are a bit harder due to the need for timing. The Adafruit interface for these grabs directly from memory address and seems well, a bit hacky. As suggested on IRC, a proper kernel module may be helpful. hint for someone else to complete :-)

The main sensor array is a set of DS18B20 sensors from fleabay (cheap if you're ordering 50 at a time) attached to the sheepwalk i2c interface 'RPI2'. These are then strung around to suit depending on location (ie, for our watercooled racks I'm going to affix the sensors directly to the flow/return lines on the watercooled racks to give us the delta-T across each set of door radiators (The BMS only gives flow/ret temp overall) which when tied to the internal temp sensors in the back of the racks should give us an idea of how well we're shifting the heat away from the machines. All this hardware comes in at less than 100 AUD per room - and some soldering time to make up the sensor chains to suit. To get an idea of the stratification (and therefore how do we position floor tiles relative to the overhead extraction vents) I'm going to put 15-20 sensors on a piece of plastic waste pipe to get a nice vertical profile - cue trip to bunnings (local DIY store) later this weekend.

Software

Hat-tip to the excellent MQTT people - nice n simple to use a python publisher script to send to a mosquitto broker on the lan. From there we can republish to Xively (useless as it doesn't respect timezones in the plotting so I can only see data I sent 8h ago...), Google spreadsheet (in a refactor of the original adafruit idea, and currently to a simple python curses console

Once we go into production and kit is running properly I plan to use the broker for all the machine status info and we'll dispatch accordingly for alarming.

More info and code will appear at https://github.com/ivecops/EnvMon

Radio Scrobbling via MQTT

Since I often listen to the most excellent Soma FM during the day (go support them, it's worth it!) I often wish that I could go and stash some similar tunes to listen to when I'm not online. To do this, I sell my soul to CBS and use last.fm to generate similar / listened to by others recommendations.

Sadly Rhythmnbox doesn't scrobble radio stations (even though the scrobble API has a flag for this
track.scrobble(chosenByUser=0) to indicate that its been chosen by a radio service), despite it updating my 'now listening' status on IM. So, in a geeky overkill solution I decided to save time in the long run and use a pub/sub system with MQTT. Oh, and use some python and twitter along the way...

The design is that I have an MQTT publisher that uses the tritter streaming api (via tweepy) and filters for all the somafm twitter streams that Rusty pushes with BigUrl. This gives me near realtime announcements of the start of the track being played (after some trivial split / strip manipulation)

ie

justcovers       Pat Boone - Enter Sandman  (2012-06-25 07:20:30)
digitalis        Zephyrs - Stand Round Hold Hands (Ulrich  (2012-06-25 07:20:37)
secretagentsoma  Eat Static - Love Truncheon  (2012-06-25 07:21:02)
beatblender      Kerry Chandler (Lazy Dog Ben W - Isis  (2012-06-25 07:21:29)
sonicuniverse    In The Country - Only The Birds Can See Us  (2012-06-25 07:21:29)

..which I can then publish to an internal MQTT broker using mosquitto python bindings.

In a separate process I have a subscriber that I can point to the broker and 'subscribe' to the radio station when I'm listening and it scrobbles that information to last.fm. 

All in, an interesting sunday evening work.