EMONWRT2
EmonWRT Wifi Energy Monitoring Device with OpenWRT and Emontx.
EmonWRT is a one unit system for energy monitoring. It measures usage of an electrical installation and post data on a server (Emoncms). You can then view the data on your computer or phone.
It combines the Arduino based microcontroller and OpenWRT wifi module together. EmonWRT interfaces with sensors like Current Transformers/ Temperature and Voltage.
This is a powerful system for a small installation like a domestic house with an access to the internet.
The EmonWRT is currently for sale here.
- Simple to use with web interface for configuration.
- Connect with Wired or Wifi.
- Wall mountable.
- Single box system.
- Open source components OpenWRT and Arduino.
EmonWRT vs Raspberry Pi. The main motivation for developing the EmonWRT was to increase robustness. For the long run the RaspberryPi solution can become vulnerable due to the operating system hosted on a SD card. High quality SD cards can be used but a higher risk of failure still remains. The EmonWRT contains the operating system on an embedded flash memory and will solidly keep on running.
Technical Specifications
- 4 Current Sensor Ports
- 1 Temperature Sensor Port
- 3 AC/AC Adaptor Port
- 1 Ethernet Port
- 1 MicroUSB Power Supply port
- Operating System: OpenWRT Barrier Breaker
- Micro Controller Unit: Attiny84 (Arduino)
- Current Sensor burden resistor: 24Ω
- Wifi (internal antenna)
- Dimensions: 106x86x19mm
Recommended Sensors
Current: SCT-013-000
Temperature: DS18B20
AC/AC Adaptor: 77DB-06-09
Defaults
IP Address (LAN): 192.168.2.1
IP Address (WAN): DHCP
Username: root
Password: admin
Hardware
Internally the Arduino mcu collects data from sensors on the ADC port and transmit them to the OpenWRT module via serial interface.
Then the OpenWRT module transfer all data to the specified web server (Emoncms, thingspeak etc...) using conventional ethernet protocols.
The Arduino sketch can be uploaded to the board for custom applications. Default sketch are available on this page.
The configuration of the unit is quite simple using the Luci web interface that comes with OpenWRT. One can at easy configure the EmonWRT to connect to a home wireless router.
Configuration
The web interface
OpenWRT uses Luci for configuration. The EmonWRT has a page on Luci where APikey, emoncms server and node ID can be configured.
Apikey is the long number that identify the account on the Emoncms server. It can be found on the emoncms server in the API help page. The Read & Write apikey key should be copy pasted here.
EmonCMS Hostname is the location of the emoncms server to use. It can either be emoncms.org or your own server. If using your own emoncms server you might need to indicate the full path here. e.g. 192.168.1.50/emoncms/
Node ID is a number that identify the device. If you have several EmonWRT (or emontx) you can change this number here to differentiate between them on the server.
Background Configuration
The actual configuration is saved in a text configuration file /etc/config/emonwrt.
Arduino Sketch
The emontx has an atmega328 which can be programmed with the Arduino IDE. To upload a sketch you will have to open the EmonWRT box and connect a FTDI/USB cable to the FTDI port on the emontx. The default arduino sketch can be found Here. The library from OEM is also needed for this. It can be found here. This sketch will output three current sensors (CT1 2 and 3) and temperature.
Serial String Format
If you decide to write your own sketch you need to output on serial interface the data in the following format:
EMONWRT CSV_DATA
CSV_DATA being each output field separated by a comma. Here is an example for three fields:
EMONWRT 75,45,4058 EMONWRT 79,51,4060
This format is necessary for the forwarder program in the WR703N.
Data Forwarder script
The WR703N router has a script written in bash to grab the data from the EmonTX and send them over to the emoncms server. This script is called emonwrt_forwarder.sh. You can download it below.
The script is launched when the WR703N boots up using init.d mechanism.
RF Gateway
The EmonWRT can optionally be used as a gateway for other RF sensors. Using the RFM12B module the EmonWRT will read and receive all data from other sensors equipped with the same module (other emontx, emonTH, tinyTX etc...).
To enable the RF forwarding from your sensor to EmonCMS one should set the RF variable to 1 in the Arduino sketch.
Internally the emontx inform the forwarder script using a RFNODE header in the serial string. The format is as follow:
RFNODE <node_ID> <csv_DATA>
For example with a node ID 10 the string will look like:
RFNODE 10 165,0,0,2781 RFNODE 10 168,0,0,2781
Files
Default EmonTX Sketch - Ct123 & Temperature
emonwrt_forwarder.sh
Configuration file
Howtos
Install/Update EmonWRT on WR703N
Start the forwarder in debug mode
Timeout for some wifi connections
Version History
Sketch
1.6
EmonWRT Software
1.3
- Support for OpenWRT Attitude Adjustment
1.4
- Support for OpenWRT Barrier Breaker