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emonLight

It's a simple home energy monitor for Raspberry Pi, optimized for simplicity and cost effectiveness. Source code is available at github. Features:

  • Power usage levels are read from one or more standard energy meters with pulse output
  • Power usage is collected and can be sent to your own server running emonlight-web or to emonlight demo site. Output for emoncms.org is supported too.
  • Multiple sources and multiple servers are supported
  • Able to drive a buzzer for signaling high-level usage with configurable soft and hard thresholds
    • soft threshold: 1 to 3 intermittent beeps signal depending on proximity to time limit; default for soft limit is set to 3300 Wh with a time limit of 3 hours
    • hard threshold: 4 to 6 intermittent beeps signal depending on proximity to time limit; default for hard limit is set to 4000 Wh with a time limit of 4 minutes

Hardware

  • Raspberry Pi
  • energy meter with pulse output
  • Raspberry's 5V power supply (minimum 1200mA)
  • optional buzzer
  • wiring for pulse output and buzzer

Raspberry

Any version will do, software has been developed using a Raspberry B+.

Energy meter

Any energy meter with pulse output is fine, see some examples below:

Information about pulse output can be found here http://openenergymonitor.org/emon/buildingblocks/introduction-to-pulse-counting.

Buzzer

The buzzer is driven by a simple GPIO 3.3V on/off signal, no PWM handling at this time. Due to the constraint above, be aware that buzzer must have:

  • built-in oscillator
  • driven by 3.3V

Here an example of such a buzzer https://www.adafruit.com/products/1536

Wiring

Pulse output can be directly connected to GPIO pins, be warned that internal pull-up resistance have to be enabled for GPIO pin used.

Energy meter Raspberry GPIO
S0- GND PIN
S0+ GPIO PIN

Default pin for pulse reading is GPIO 17.

Buzzer can be directly connected to GPIO pins.

Buzzer Raspberry GPIO
PIN - GND PIN
PIN + GPIO PIN

Default pin for buzzer is GPIO 3.

Software

Software is written in C.

Development has been done with netbeans connecting to a raspberry B+ device running Raspbian, but any other distro will do.

The build system is based on Makefile.

Program doesn't require special privileges, When it is executed as a daemon it defaults to use system wide configuration in order to be handled by a debian-compatible sytem installed service.

Raspberry GPIO configuraton must be performed before program can be executed, otherwise it will fail asking for root permission.

Required Libraries:

Build and install

  • connect to your rasperryPi and open a shell
  • install software for C compilation
  • install git to download the software

install wiringPi library following instruction [here] (http://wiringpi.com/download-and-install/)

install libraries

sudo apt-get install libconfig-dev libcurl4-gnutls-dev

retrieve source code from github

git clone https://github.com/sermore/emonLight.git

build

cd emonlight
make

install system service named emonlight

sudo make install

setup configuration for service; default pins are GPIO 17 for pulse output reading and GPIO 3 for buzzer control; if you need different setup you have to change:

  • /etc/default/emonlight which contains GPIO pins and queue configuration
  • /etc/emonlight.conf which contains program settings

start service

sudo service emonlight start

stop service

sudo service emonlight stop

GPIO configuration

Configuration of GPIO pins must be performed before first program execution.

# configure input pin for reading pulse signal
gpio -g mode 17 in
# enable pull-up resistance for GPIO 17
gpio -g mode 17 up
# enable interrupt sensing for falling edge signal on GPIO 17 pin
gpio edge 17 falling
# configure output pin for buzzer control 
gpio -g mode 3 out
    #export above configuration in order to be handled by program without privileges
    gpio export 3 out
# set to zero level buzzer pin
gpio -g write 3 0

configuration file

/etc/emonlight.conf or $HOME/.emonlight

# WARNING this program can drive gpio pins only after pin configuration is made by running gpio 
verbose = true;

sources = ({
    # gpio pin for pulse signal reading
    pin = 17;
    # number of pulses equivalent to 1 kWh
    pulses-per-kilowatt-hour = 1000;
}, {
    pin = 3;
    pulses-per-kilowatt-hour = 1200;
});

servers = ({
    url = "http://emonlight.reliqs.net";
    protocol = "emonlight";
    map = ({
        pin = 17;
        node-id = 1;
        api-key = "key-3";
    }, {
        pin = 3; 
        node-id = 2;
        api-key = "key-4";
    });
}, {
    url = "http://emoncms.org";
    protocol = "emoncms";
    map = ({
        pin = 17;
        node-id = 5;
        api-key = "key-1";
    }, {
        pin = 3; 
        node-id = 6; 
        api-key = "key-2";
    });
});

# gpio pin to drive buzzer
buzzer-pin = 3
buzzer-source = 17
# power thresholds
power-soft-threshold = 3300
# 3 hours
power-soft-threshold-time = 10800 
power-hard-threshold = 4000
# 4 minutes
power-hard-threshold-time = 240

# if a data-log configuration is found then all data received is saved to this file
data-log = "/var/lib/emonlight/emonlight-data.log"
# store of status persistent information: time and count for last pulse received
data-store = "/var/lib/emonlight/emonlight-data"