Power monitoring system in under 4 hours

Fri, Sep 18 2009
Posted by Jonathan Oxer Apologies in advance if this sounds a bit like an ad. It's not intended to be, but I need to give some context which means mentioning a couple of companies. Yesterday I experienced a perfect example of the sort of rapid prototyping that Arduino makes possible. My company (Internet Vision Technologies) does web-based business process systems, online applications, data visualization, etc, and we're doing a bit of work at the moment with energy monitoring among other things. We're working with the clever folks at EkoLiving who are experts at collecting data from high-end power monitoring / management systems, but yesterday we needed a system to feed some semi-sensible data from multiple power circuits into an online datalogging system so we'd have something to display in our visualization front-end for demo purposes. I didn't need the sort of accuracy required for a utility-grade system used for, say, billing customers for their power usage, just something that would give some representative figures as a reference point with perhaps 10% accuracy. So I grabbed a couple of bits from Jaycar and put together this: I left the office at about 11:30am to head off to Jaycar where I grabbed three C-tick approved / 400A-rated current clamps, an LCD module, the box, and some 4mm sockets. Back home to use my workbench and add in some things I already had including an Arduino Duemilanove, a WiShield, a prototyping shield, some ribbon cable, and some miscellaneous M3 nuts and bolts. Fitted everything together and was back in the office in time for a 2pm meeting with the hardware 100% complete. Had the meeting, then back to my desk where about another hour later I had the software up and running based on the sampling and RMS calculations from jarv.org/pwrmon.shtml but with the addition of local display on the LCD and remote reporting via the WiShield to a web service. I've wired it up for 3 input channels because that's how many current clamps Jaycar had in stock, but of course the Duemilanove has 6 ADC inputs so I marked the case to fit 6 pairs of sockets and then only populated 3 pairs. I'll probably add the other 3 channels next week when the electricians come to the office to separate out the circuits in our switchboard to let us get all the current clamps in there. So, total time required from my "stuff it, I'm just gonna make one" remark to complete, functional system as you see it in the picture: well under 4 hours, including the trip to Jaycar to get the parts. Now *that's* rapid prototyping! And that's why I love Arduino.