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"

sermore / emonLight