My first step in building my home energy monitoring system is logging temperatures. My first attempt used a simple thermistor. I tried to use a long cable so I could locate the Arduino in the basement and the sensor closer to the middle of the basement. This didn’t work since the resistance in the wire skewed the sensor readings way too much. I’m currently logging the data using the thermistor mounting on a wire problem about 6 inches from the Arduino.
I use an Arduino Uno with the ethernet shield. I log data to Pachube. You can view the output here.
The first chart is the temperature, the second is static randomness. I wrote the sketch to check and log multiple sensors but I haven’t connected a second probe yet.
I also track failed attempts at logging data. When the number resets to zero I know the power was disconnected to the unit. I plan to track number of updates, but as you can see, that counter doesn’t increment yet. Another thing to add to the list.
The output is in tenths of a degree. The data is logged every 10 minutes. The temperature in the basement varies from about 16 degrees to 10.9 degrees depending on the temperature at the wall. I am going to move the Arduino and sensor away from the stone wall, but first I have to wire a new electrical outlet in the middle of the room.
I’m current waiting for my second Arduino to come in with a couple of Dallas temperature sensors so I can start working on a better version using the 1-wire protocol. This will allow me to take the temperature in each unit as well as the basement. More on this to come.
Maxim (Dallas) sent me a great package of free samples that I’m planning to use. The set back is that they are much smaller than I anticipated. They look a lot bigger in the information brochure. They also send me Surface Mount versions. In order to use these, I will have to build a Printed Circuit Board. I plan to use Sparkfun to manufacture the board, but of course first I need to design a PCB.
Before I can do that, I need to draw the schematic, so that has brought me Eagle. So my next steps are:
- Learn to use the Eagle Schematic Editor
- Learn to use the Eagle PCB board program to make a gerber file.
- Order the board.
- Give up caffeinated coffee completely.
- Learn how to soldier using a magnifying glass.