I've recently become somewhat obsessed with understanding how much electricity our home is using. There are certainly commercial offerings to allow you to monitor the power consumption in your house and there are also award winning kits available but these don't quite cut it for me for a couple of reasons:

1) Why buy something when I can frustrate myself? In all seriousness, I've been looking for a project that will hook together a number of different interests as well as to being sufficiently large that I have to break the problem down into a number of discrete parts.

2) A lot of the solutions look at monitoring by measuring in series with an appliance (or extension cord) from a plug as oppossed to the whole house. I think the ideal solution is a combination of both but the majority of documented projects concentrate on the plug side of things.

3) The UK is somewhat behind the curve in offering smart metering and measurement so I want to provide a local example for a change!

In the UK, as houses are slowly upgraded to new digital meters, the handy hacker has access to a means of monitoring without worrying about induced electric fields (e.g. measurement through Hall effect sensors) or through cracking open the meter itself (which would no doubt get you in trouble if not shocked!).

"What is the capability?" I hear you cry, well it's an LED that flashes for each 1/1000KWh consumed from the mains and as its a BSI certified product its reliable.

So this instructable documents the process of creating a device that monitors the number of flashes being produced by a UK Electric meter and sending the count to a computer for data logging and visualisation.

The system consists of two parts, a unit that sits in the meter cupboard (based around a photdiode, an Arduino, a DS1307 Real Time Clock and an XBee wireless board) and a computer based reader (an XBee via a USB explorer board and a Mac OS X logging application).

It can be used in conjunction with other solutions such as adafruit's Tweet A Watt to provide a very detailed picture of consumption within your home and gets you one step closer to having a home smart grid.

From my perspective this project has green credentials because if you can't measure your consumption, how can you begin to understand your impact? As an added bonus, if you can see when you use your electricity, you can start looking at how to cut back, not only saving the earth, but saving money too.

Step 1: Watt you'll be needing

Buying parts in the UK is an interesting process as there isn't as broad a base of suppliers who are targeted at people like you and me.

In addition, I also bought the parts over a series of months as I switched around in terms of what projects I wanted to try and complete (as well as watching the GBP/US Dollar rate slide from nearly $2 to $1.35).

I've decided to group the parts list by the supplier that I used. I am pretty certain that people will have their own preferred supplier and I would also plug Octopart if you live in the US to find your own bargain.

2 x XBee 1mW Chip Antenna
1 x XBee Explorer USB
1 x Arduino NG
1 x Arduino breakout board

Adafruit Industries
FTDI cable

Tinker.it (Actually a UK provider of some Sparkfun boards and Arduino training)
2 x Breakout Board for XBee Module
4 x 2mm 10pin XBee Socket

Farnell UK
1 x Photodiode
1 x LD1117 3.3v voltage regulator

1 x DS1307 Real-Time Clock Mini Board

1 x 3mm Red LED
1 x 3mm Green LED
1 x 3mm White LED
1 x 10K resistor
1 x 1K resistor

From browsing through the various suppliers its obvious that there are variations in price and shipping etc. so I guess its a case of going with what you feel most comfortable with.
Hi, any chance to post the actual sketches to enable copy and paste? Thanks!
what is xbee by the way? <br>thanks! <br>marC:)
Hi marC<br><br>XBee is Digi Internationals brand name for products based around the low power power 802.15.4 protocol. XBee allows you to connect low power embedded devices together wirelessly.<br><br>The books 'Making things talk' by Tom Igoe and 'Wireless Sensor Networks' by Rob Faludi are both good reads and cover XBee<br><br>M
check out my instructable on how to get the data online.&nbsp; heres my power consumption website, <a href="http://www.sites.google.com/site/19acussen" rel="nofollow">www.sites.google.com/site/19acussen</a>&nbsp; works great on my iphone :p
Very interesting but have you never herd of a clamp meter, just hang it off the phase and it dose the rest for you... about £25, but still clever idea!
Hoddy, Completely agree with you (and in fact I sourced some hall effect sensors as a back up to the photodiode circuit) but where's the fun in that :-)
Hoddy, Completely agree with you (and in fact I sourced some hall effect sensors as a back up to the photodiode circuit) but
My admiration goes out to you! This is serious business - good work. Keep it up.
Pretty interesting Instructable!

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Bio: A frustrated geek who has a day job that doesn't allow for a great deal of tinkering
More by mcloke74: Watts-your-consumption? - Wireless Power Meter
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