Monitoring how much power we use is getting quite popular, most of us have seen the Kill a Watt device before and there are also whole house versions of the Kill a Watt. If I ever get around to it I would like to build a whole house monitoring system that can show me some simple stats of power use, something like how much power was used today and in the last hour. I would also like to have a way to enter the cost of electricity so it can chime every time I have used a dollar of power.
Bill Porter has designed and built a DIY Power Consumption Monitoring System which uses an ATtiny 85 microcontroller to keep track of power usage in his house. He is using two current clamps that feed into his circuit. He has made it wireless so you could use this data anywhere in the house. He has even made a cool LED sign that is being used as a display output from the system. If you would like to build one of your own Bill has provided everything you should need on his site.
“The ATtiny85 will repeatedly sample the volts ADC pin for over a full period of the 60Hz sine wave. The peak value of the samples is remembered. Repeat for both current clamp ADC pins. After the max values are captured, the ADC clock is increased for faster sampling, with higher errors. To measure frequency and power factor, I used a 8 bit timer that I extended to 16 bit in software. Using the timer, I measure the difference in time between two peak values of the voltage waveform. Then, I measure the difference in time between a peak value of the volts waveform, and a peak value of the current clamp waveform. “
