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The SEGmeter specification

published, Jun 8, 2010 12:01am
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The SEGmeter Arduino shield turn Arduino into a smart meter. It combines a number of useful features, such as 6 channels of energy measurement, temperature sensing and a reed relay control. In addition, there is capability to support Zigbee for wireless communications to an internet gateway device as well as a small prototyping area for added magic.

smartenergygroups.com also provide a range of compatible current senors and other components to help build out a complete smart metering solution, including a nice website to help understand and visualise energy usage.

So, lets's get on with the specs!



  • 6 Analog inputs with 6 low pass filter circuits,
    note, a non populated low pass filter will allow alternate analog inputs.
  • Digital input for a one wire temperature sensor on pin 5

Digital outputs

  • A single channel onboard reed relay to enable the switching of low power circuits from the Arduino on pin 7

Power Interfaces

  • On board regulator to take the Arduino supply voltage, in the range of 12-5V down to 3.3V capable of supporting the power requirements of a 900MHz Zigbe.


Serial interfaces

  • 4 Pin interface for serial connection breakout to enable direct connection to an Asus Router, with pinout on the shield being, 5V – RX – TX – GND.
    note: to use this config for direct connection to an Asus Router, the Router will need to be wired up for 5V, not 3.3V and power from the router will power the Arduino.  Other router models are supportable with a suitable adaptor cable connecting the relevant pins.
  • 4 Pin serial daisy-chain interface with pinout being, Pin 0 Rx – Pin 1 Tx – Pin 2 Rx – Pin 3 Tx
    This will enable downstream arduino's to send and receive on pins 2 and 3.

Zigbee Interface

  • Enable direct plug in of a MaxStream 20 pin type Zigbee directly onto the shield.  This will includes level shifting of logic signals to 3.3V



  • Supports a watchdog circuit, to be implemented by the maker capable of resetting the Arduino.


  • Red Power LED to indicate power is being supplied to the arduino
  • Yellow Status LED on pin 13 to indicate normal operation of the arduino
  • Red Relay Status LED on pin 7 that will light when the relay is closed

Form Factor

  • The form factor for the shield shall be the same footprint as that of an Arduino Duemilanove.  The Sparkfun Arduino-Pro 5/16Mhz is the preferred low cost Arduino platform.

Prototyping Area

  • Because we are making open hardware, we've provided a small prototyping area for people to get imaginative and build some other magic into their SEGmeter.  Examples could include a shift/latch to support an LCD display.


Electronic Components

  • All electronic components, with exception of the 3.3v power regulator are through hole to allow for ease of assembly by people with moderate soldering skills.


So that's it, SEGmeter in a wrap.  Whilst it's not a revenue grade billing meter capable of all things, it is however a very hackable, easily buildable energy efficiency device that's internet connectable.




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Hi Sam!

Flukso is an open-source hardware/software community metering project, quite similar to SEG. We want to lower our energy (electricity) consumption through better visualisation, feedback and benchmarking against peers. Our Fluksometer blends a router board based on an Atheros 802.11b/g chipset with an AVR-based sensor board. The sensor board accepts split-core current clamps as wel as S0-type pulses from kWh meters. See this blog post and presentation for an overview, our code repository is on Github. Should you guys feel like exchanging some experiences or ideas, let me know.

Cheers, Bart.

Great to find your site this afternoon.  I am doing very similar work in Berkeley, CA based on info from MightyOhm's ASUS WL-520GU to Internet Radio and Adafruit's Tweetawatt.

I am mostly a business software developer (C#, .NET, Web Services, SQL Server) but now I'm learning about hardware, xbee, arduino, openwrt, python, sensors, energy, etc.

My framework looks much like yours; sensors, zigbee, ASUS to internet web services (and to twitter; like the tweetawatt).  My design so far has not required an arduino although I have one and have played around with it.  I am looking to have more of a one to one connection between a sensor and an xbee transmitting to a single xbee receiver in the ASUS.  The ASUS is sending data to a simple SOAP web service (plan to change to REST when I get time).

Ideally, I would like to put watt meter sensor on every plug load I have and collect the usage of every appliance, light, etc in the house.  That means bringing the cost way down...  The xbee seems to be the limiting factor for now; don't think I'll be building those anytime soon.

Question, please: Looks like you're using the 900Mhz Zigbee.  I went with the simplest xBee modules from Adafruit (about $20).  How are those working and do they use a similar setup to the xBee Series 1?

Also would like to know what kind of sensors you have developed.  I've got the tweetawatt and a temp sensor and I've ordered a gas sensor.  I have plans to build a water leak sensor as well.

Great to see your enthusiasm for this kind of application.  I'll keep you posted on my progress, slow as it may be... 

Is there a circuit diagram / schema available for download somewhere? I would be specially interested in how you solved the sensor connection with low-pass. Is that 3,5 mm stereo audio jacks with additional capacitors?

Hey Marian,

Sure, head over here:


Build guide that has the circuit and parts

Its a simple band pass, a high pass that removes DC offset then a low pass to remove extraneous noise in the AC signal.


Hey - cool stuff, guys! You've got me interested, for when I stop renting and buy my own place. Question - https transport of data, I'spose? In other words - there are many commercial 'smart' meters available through the various utilities, and with quite a few of them they're either not password protected, or use plain http or even worse communication protocols, basically allowing anyone to listen in and find out (if they're clever enough) what kind of TV or PC or whatever you have and when you're home or not. So, it's cool to see private energy consumption data being collected and being processed on bit of a clever server, but I'd like it to remain private, non-of-their-business as you know what I mean. How do you handle this? /ojh

Hey Ot,

How whole app runs https for all the energy stuff and other things like logins etc. (blogs and forums aren't https forced) 

All the data collected is yours and it's your choice to share! And it's totally independent of the utility company too.

Sam, @samotage

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