Like any good project, this one started with a need. I have a home which has a radiant floor heating system. I’ve never had a heating system of this type, and as such, I tried to learn everything possible about the system. My only concern was the operation of the system when I wasn’t at home. Clearly I needed a way to monitor the performance of the system without actually being on site.
My first attempt started with a couple of temperature sensors located in a few rooms to monitor room temps. Here’s where the problem suddenly became difficult. Because I try to minimize energy consumption, I wanted a way to operate the temperature sensors without a computer running 24/7.
Even with the most efficient computer, I’m still out $2,000 for the computer, plus the continuous cost of 10+ watts of power. One example of a computer that can run under 10 watts is a
Sony Vaio UX-390, but this is certainly not a web server. I thought I could use an existing 802.11-g network in my house, and send the temperature data directly from the sensor to a remote computer. Unfortunately, the only thing even remotely close to this was a temperature sensor from
G2 Microsystems or
Point Six. Both are in the hundreds of dollars of cost per sensor! Ouch. I tried searching the internet numerous times for ethernet based temperature sensors, wireless temperature sensors, and even home monitoring temperature sensors - all without any luck. Clearly I needed something else.
Further research led me to a web site named
Our Cool House. Phil, the owner of this site, has designed
and built a device called a Web Energy Logger (WEL). This device, which includes its own built-in web server (albeit not wireless - yet), costs about $350 and can monitor tens, if not over a hundred, sensors. They can be temperature sensors, current sensors, and many others. Although the device is a little expensive, it is apparent that Phil has put a lot of time into the design and software used by this device. It functions both as a web server as well as a data logging device (but the data is stored at
www.welserver.com. The device uses a communication bus called 1-wire, which was original developed by Dallas Semiconductor for low-speed data signaling and power of a single wire. The 1-wire name is a misnomer, the sensors actually use two wires, but only one wire carries the data and power for each sensor, the other wire is ground.
First, I needed to design my 1-wire network for the WEL to monitor. I started by creating a list of locations where I wanted to monitor the temperature. My list looked a little like the following:
Heat (Air) Exchanger
Fresh Air In
Stale Air In
Stale Air Out
Fresh Air Out
Water Heater
House Hot Water
House Cold Water
Radiant Floor Heater Water
Room Temperature
Master Bedroom
Living Room
Kitchen
Bedroom #1
Bedroom #2
Family Room
Miscellaneous Temperature
Outside
Attic
Floor Slab
Garage
I purchased 18 temperature sensors (DS18B20-PAR) and I plan to solder them up myself. Although they have three leads, only two of them will be used. I also purchased several current sensors to monitor whether a motor or heater is running. I plan to use my home’s existing telephone wiring, which all comes to a connection point in my garage. I’ll disconnect the couple of circuits I’m actually using for phones, and the rest of the wiring will then become a central hub for my 1-wire network.
My favorite part about the WEL device is the ability to overlay my temperature sensor readings on top of an image that I supply. I immediately thought of Google’s SketchUp software, which is free. This allowed me to create a three dimensional view of my house. I will overlay my sensor readings on top of this image with the tools provided on the WEL site.
All 18 of the temperature sensors arrived and I started to construct my sensor network. After installing about three temperature sensors, I wished I had opted for the pre-soldered sensors from www.welserver.com. This would have saved a considerable amount of time and frustration attempting to solder tiny connections, while making sure everything had enough heat shrink tubing over them to prevent short circuits.
I tried to wire everything in a star configuration (one main twisted pair cable with multiple lines running outward from one central point), which was recommended when I purchased the WEL device. Some sensors didn’t work well in this configuration, so there are a few branches on the main leg of my star network.
I connected to my router tonight, and began testing and updating individual sensors. Oddly enough, everything seems to be working. No need to configure the WEL IP address or any other network configuration! The sensors came online one at a time, just after I plugged them in. Temperature data and run-time data began flowing immediately. I couldn’t have asked for a better installation.
I went to the WEL web site, and began to specify how I wanted my log file to look, and how I wanted my data displayed on my personal image (see house layout above). I have some serious configuration to do here, but once I place everything, it should be fairly permanent.
I fully expect to add more sensors in the future, now that I’m getting some good data. This really surpassed my expectations! Installation was a breeze, especially since I used the yellow/black wires from my already-installed telephone jacks. The red/green wires supply my phone server, and neither is interrupted by the other. I have to give this project a 10 out of a possible 10 point scale. Way to go Phil, this is a great device! It is obvious a lot of time and effort went into this product.
Update: My device has been working well now for several months. I have found a couple of issues that Phil has been working hard to fix. First, if you live in a very cold climate, like Minnesota, you will have scaling problems on the graphs when it gets down to -15 degrees or below. Second, it appears that the longest history recorded is only about 12.5 weeks. Thus, if you plan to record temperatures over a year, you may have to keep the data yourself.
The WEL server web site now has location information for the WEL devices installed world-wide. It is kind of fun to see everyone who has purchased these and how they have put them to work. Check our ours in northern Minnesota. Phil has also graciously added an alert function, to indicate things like a low temperature alarm. Only one alarm is allowed, but hopefully he will increase this in the future.
Overall, the problems are minor ones and the pluses are major - I’m still very impressed. You can’t find a better internet based temperature monitor for your money. This one just works.
