Tag Archives: sensors

New Temperature Sensors

I got my self some new temperature sensors for my hacked together home thermal monitor. The software that runs this is still aweful, that’s on my project list. But at least now I’m able to figure out thermal variance inside the house, which is broader than I’d have expected.

A couple other changes were made in loading in the new sensors as well.

The outdoor temperature sensor is now on the North side of the house. This should minimize the amount of the day sunlight can hit the thing. While Oregon Scientific believes it can live in direct sunlight, my experience over the last two weeks is that it definitely can not. You get a 4 – 6 degree spike under direct sunlight. I could almost use the spikes to generate a map of the trees on the south side of the house based on when their shadows hit the sensor. The short of it, my reporting to Wunderground should be more accurate now.

The cold frame sensor is still at the far edge of receptivity, especially with the amount of earth it needs to go through. I build a tin foil reflector which seems to be helping a little, but it still drops out from time to time, generating the square waves in the curve. Not much I can do about that.

If you want to know more about this project, this post is probably the best starting point.

Sniffing Oregon Scientific Weather Sensor Data

A few years ago I bought an Oregon Scientific wireless weather station.  It’s a nice way to keep an eye on what’s going on outside.  The unit supports up to 3 of these remote sensors (shown here), and aggregates it at a base station.  It doesn’t have a computer interface, so while it displays nicely in the living room, I can’t get access to that data.

Once upon a time I bought some 1-wire thermo sensors that I was going to wire that into my computer for data collection.  After the house was hit by lightning, I got far more gun shy about running conductive cables from the outside to a computer.

It occurred to me recently that there was good odds that someone must have figured out to sniff that wireless communication.  These aren’t complicated devices, and Oregon Scientific seems to be letting different generations of sensors work with different generations of head units, implying that they have some pseudo standard protocol.  It would also solve my spark gap problem, as I could gather this data without any wires connected to the sensors.

After some googling I discovered that yes, these devices are operating in the 433 Mhz band, and yes, thanks to the folks at rfxcom, there is a unit out there which will receive this and spit it out in a reasonable usb interface.

Under Linux, this information can be very easily decoded with the heyu program.  This is really more of a command line system for home automation, but it also includes the rfxcom protocol and the decoders for just about everything Oregon Scientific makes.

After plugging in the rfxcom device, it took me about all of 30 minutes to get heyu compiled and configured for my devices.  The first time you run the heyu monitor you’ll actually get big hex strings which are the raw data.  Once you tell heyu what kinds of sensors they are, you’ll get it decoded in much more friendly units.  Here are the relevant lines in the heyu config file:

TTY	dummy
TTY_AUX  /dev/ttyUSB0  RFXCOM
ALIAS Sensor1 A1 ORE_TH1 0xB1
ALIAS Outside A2 ORE_TH1 0x83
ALIAS Sensor3 A3 ORE_TH1 0xCE
ORE_TSCALE Fahrenheit

After configured and running, I now have sensor data being collected continuously:

gallifrey:~> heyu monitor
02/25 21:49:54  Monitor started
02/25 21:50:11  rcva func      oreTemp : hu A3  Ch 3 Temp 58.6F (Sensor3)
02/25 21:50:11  rcva func        oreRH : hu A3  Ch 3 RH 42% (Sensor3)
02/25 21:50:20  rcva func      oreTemp : hu A1  Ch 1 Temp 43.7F LoBat (Sensor1)
02/25 21:50:20  rcva func        oreRH : hu A1  Ch 1 RH 54% LoBat (Sensor1)
02/25 21:50:22  rcva func      oreTemp : hu A2  Ch 2 Temp 34.3F (Outside)
02/25 21:50:22  rcva func        oreRH : hu A2  Ch 2 RH 87% (Outside)

The next steps here are going to be gathering this into something that I can use for graphing.  I’ve now got all the sensors I was looking for to be able to build my better thermostat brain.  Next steps will be tying this all together and starting my graphing.