an Arduino based desktop power meter

This page is all about my attempt to build a desktop scale power meter, based on the arduino platform.

Latest (Updated 28/10/09)!

I've completed the first pass of the design, did the CAM scrips in EagleCad and sent it off to those nice people at PCBTrain.co.uk to make it for me on the 13th October. All the current files in downloads are as my first 'production' version. I'm still waiting for the boards to arrive (they're being posted Royal Mail unfortunately). I've also made some changes to the BOM, adding parts I don't have in my big bag full of parts, so I'll need to order a few bits & bobs before I can start soldering up the first one. Exciting! Today I also ordered a stack of books on Python, Apache and MySQL to sort out the PC end of the integration.

Progress as of 27/09/09

I've had a think about the things that the next version of this board should do. The list is here.

Completely revised the PCB layout over the weekend with some significant (hopefully!) improvements. The Eaglecad autorouter now does 100% of the routing, with a little persuasion. The main issue I came across during design was the need for very large track widths to accommodate the 13A from a socket outlet, hopefully this is covered by having wide tracks on both sides of the board. I did look at introducing an earth/ground grid (just like on the Arduino board) but decided not to as it didn't actually do very much due to the large clearances required for the mains tracks. Also worth noting, the transformer seems to be the wrong way round (tracks would be shorter if it was flipped 180 degrees) but this seems to make the autoroute more complicated! All the new stuff is on the download page. Should be ready to get one made any day now.

Go to the download page to download the circuit diagram and pcb layouts. 

Also, I stumbled upon a reference design here and here, (maybe it was in the data sheet all along?) though they're all in chinese so I'm not exactly sure what to make of them till I can get it explained by a chinese speaker.

Progress to date: 

27/09/09, hopefully all the things wrong with the version from the 9th September have been looked at and fixed. I've done a 'mock up' using some cardboard and a scale print out. A picture of the mock up is here. There are still a couple of tracks that look a bit too small/rough, but generally everything is at least 12mil wide, which should be plenty. The AC tracks carrying 13A are now double sided and 160mil wide with a decent separation between them. 

09/09/09, I've done a preliminary circuit design and put the components on an Arduino shield. So far I haven't got round to verifying the design in any way shape or form. Click here to see the component list.

To do:

Verify design a bit more

Check the PCB design is ok

Make one!

Test + write arduino code.

Background:

The idea is an accurate desktop scale power meter, suitable for measuring individual power usage at (say) a desk. Arduino is a great platform, so it seems like a good thing to base the design on. The idea is to make a plugable device that can be slotted on top of the arduino, called a shield. The principle of this shield will be to work with the Bluetooth Arduino and the USB Arduino duemilanove. The other 'big idea' is to include a power supply on board which can drive the arduino in both cases - specifically this is 'challenging' because the bluetooth arduino doesn't accept much above 5V using it's onboard regulator. The duemilanove accepts a wider range of voltages, so no problem.  Thanks should go to Duncan Wilson for his support in encouraging me to develop it this far (hopefully I can take it far enough to make something workable).

Why this project is a bit different to all the other power meters out there:

I've based the design on the Analogue Devices ADE 7753 IC, which is a custom measurement ASIC. This approach has a number of benefits, including having hopefully good accuracy and freeing up arduino processor and memory to do lots of other things more interesting than calculate power measurements. Communication (haven't quite got that far yet) will be over an SPI type bus or similar.. Power measurement will be via a CT, with a resistive potential divider to measure voltage. 

You can read my blog here -

James 

This project is released under the creative commons license:

Power Meter Shield for Arduino by James Devine is licensed under a Creative Commons Attribution-Share Alike 2.0 UK: England & Wales License.