Friday, June 20, 2008

Utilities - a history

Playing around with the very cool Google Docs today. I went ahead and populated a spreadsheet with my utility history. The charting features are somewhat lacking, so I couldn't do a very fancy graph, but here it is anyway:


It would be nice to annotate the graph with significant events, like the winter months during which the waste water rate gets computed, and the summer months when the AC is on. Also, it would be nice to have a dual Y axis range. In this graph, I had to multiply KWH/day by a factor of 10 to keep the ranges similar. Yucky.

I took the first steps to design an automatic reader for my electric meter and bought a IR phototransistor and an IR emitter. My fears were that a simple phototransistor would not be sensitive enough for this purpose. So far, my fears were justified. I am going to do some signal conditioning with some active filters and see where that takes us. If the phototransistor is a bust, then I will purchase a nice PIN photodiode with a built in amplifier. If THAT fails, I may have to resort to designing some sort of optics to reduce the noise level to something reasonable.

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