Remote Disconnect and Load Management using Smart Energy Meter
As the world’s non-renewable energy resources continue to deplete, there is an increasing need to protect them and produce renewable sources of energy. There is also a need for systems to distribute this energy via an intelligent and efficient energy distribution system, thus birthing the term “Smart Grid”. Smart Grid offers significant benefits for both utility companies and their consumers. For utility companies, it offers the ability to distribute energy more efficiently and to disconnect services for bill dodgers via remote disconnect. For consumers, it would enable them to get real-time information of their energy consumption, and with that information manage their loads accordingly to lower their utility bills.
In order to move towards the Smart Grid, it is necessary to replace prevalent electro-mechanical electricity meters used to measure power consumption with advanced meters—Smart Meters. Smart Meters enable various applications required at the Smart Grid. In this project, I implement a remote disconnect and load management application using Texas Instruments’ Smart Meter Board (SMB) EVM and the eZ430-Chronos Development Tool. This project was inspired by my desire to interface a relay-box I created in school with the SMB EVM from TI’s Metering Business Unit, which I am currently working for during my internship.
System Block Diagram Explanation
The figure below shows the block diagram of the application. The application consists of the SMB, a Chronos Watch Access point and a Chronos Watch, a relay box, an EZ430-RF2500 Access Point, an EZ430-RF2500 End Device, an IHD430 in-home display, a computer running a custom-made GUI, and a load.
Smart Meter Board (SMB)
The purpose of the SMB is to measure the power consumption of any load. The required AC voltage from the mains is supplied to the load through the SMB. Once the SMB measures the power consumption, it sends the information to the CC2530, ZigBee transceiver that sends the power reading to an In-home display (IHD430) through the 2.4 GHz ZigBee wireless communication.
The relay box is an enclosure to a board that houses a relay and an EZ430-RF2500 End Device with AC inlets and outlets. In this application, the SMB’s load is the relay box. The relay box has an electric input plug that receives power via its connection to the SMB’s load power-strip. The relay box also has an electric output socket through which any load (lamp as shown in Figure 1) can be connected. The SMB hence indirectly measures the power consumed by the lamp connected to the outlet of the relay box. The power to the lamp is controlled (ON or OFF) by a relay that is triggered by the EZ430-RF2500 End Device. A schematic of the relay circuitry is provided in the Schematics section of this article. If the End Device drives a logic-high through its output pin that is connected to the BJT, 5 V appears on the DC pins of the relay. The 5 V on the DC pins causes the relay to make a connection between the AC Mains inlet and the outlet, thereby providing power to the load. If the End Device drives a logic-low on its output, the necessary voltage needed to trigger the relay goes away. This causes the relay to break connection of the AC Mains inlet and the outlet, thereby disconnecting power from the load.
The IHD430 is a low-cost in home display using the MSP430 that receives the power reading from the SMB via the CC2530 and displays it on its LCD. In addition, it also sends this power reading to a computer via the RS-232 Serial Port connection. In order to transmit the information through the RS-232 Serial Port, the IHD430 must be put in transmit mode by pressing a S2 pushbutton on the IHD430. Pushbutton switch S1 puts the IHD430 in “sleep mode” and will not function as a display for power. S1 and S2 operate in toggle mode to enable/disable the above functions.
Computer Running GUI
The computer shown controls the relay via a GUI and is a bridge between 2.4 GHz to Sub 1-GHz.
The GUI receives power readings from the IHD430 through the RS-232 Serial Port, displays it, and then sends the data to the Chronos Access Point for it to send to the watch. The Chronos Access Point and GUI send information to each other via a virtual serial port. The GUI also communicates with the EZ430-RF2500 Access Point through a virtual serial port. This connection is used to send the command to the EZ430-RF2500 End Device to toggle the load power on or off. To turn the load’s power on or off from the Chronos Watch, the Chronos Watch sends the proper command to the GUI, which then in-turn decides whether to send the command to the EZ430-RF2500 Access Point to toggle the load’s power. In comparison, the GUI could turn the power to the load on or off directly without the Chronos watch.
Chronos Access Point
The Chronos Access Point is a bridge between the Chronos watch and the GUI. It is connected to the computer through a virtual serial port and to the Chronos watch through Sub 1-GHz SimpliciTI wireless communication.
The Chronos Watch receives any commands and power readings from the GUI and updates the watch’s display. The watch also sends commands triggered by pressing its buttons to the Chronos Access Point to update the GUI accordingly. The EZ430-RF2500 Access Point sends the command to the EZ430-RF2500 End Device to toggle the power to the relay’s load. It sends this command when the GUI writes a toggle state command to the EZ430-RF2500 Access Point’s virtual serial port.
EZ430-RF2500 Access Point
The EZ430-RF2500 Access Point sends the command to the EZ430-RF2500 End Device to toggle the power to the relay’s load. It sends this command when the GUI writes a toggle state command to the EZ430-RF2500 Access Point’s virtual serial port.
- Displays power consumed by a load (lamp) on Chronos watch and GUI
- Turns load ON or OFF from Chronos watch and GUI
- Displays real-time status of the relay which is in ON or OFF on Chronos watch and GUI
- Bridges 2.4 GHz communication with Sub 1-GHz communication through GUI
•Utility companies would send commands using Sub 1-GHz
•Household communication is at 2.4 GHz
- Has two modes of operation:
•Manual: Turn load on or off by pressing buttons on watch or GUI
•Auto(Trigger): Turn load off when power is above trigger and automatically enter Manual mode
-Can Set Trigger from Watch or GUI
-Display Trigger on watch or GUI
- Displays mode on watch and GUI
- Can change mode from watch or GUI
- GUI and Watch are synchronized so trigger, mode, power reading, and on or off state of relay is consistent between GUI and watch
- Disconnect watch from Energy mode and enter Watch mode by pressing a button on the GUI
- Exit GUI and disconnect watch from Energy mode when there is a power outage
Demo Preliminary Steps—Perform this sequence of steps only once:
1. Install IAR Embedded WorkBench for MSP430.
2. Open the eZ430-RF2500 Sensor Monitor Demo v1.02 workstation in the demo folder of theEZ430-RF2500 Code download.
3. Program the EZ430-RF2500 Access Point with the Access Point project code in the workspace.
4. Program the EZ430-RF2500 End Device with the End Device project code in the workspace.
5. Create a relay box using the EZ430-RF2500 End Device. See Relay Circuitry Schematic below for the schematic of the relay box.
6. Open the ez430_chronos_datalogger workspace in the Chronos Watch Code download.
7. Program the Chronos watch with the code in this workspace.
8. Install Microsoft Visual C# 2008 Express Edition.
9. In the GUI Code download, open Form1.CS.
10. Change COM11 to whatever COM port the IHD430 will be connected to.
11. Change COM3 to whatever COM port the EZ430-RF2500 Access Point would be connected to.
12. Change COM2 to whatever COM port the Chronos Access Point would be connected to.
13. Perform a rebuild.
Demo Preparatory Steps—Perform these sequence of steps before each demo:
1. Connect load to Relay Box.
2. Connect Relay Box as Smart Meter Board’s load.
3. Verify that there is no short between the Smart Meter Board’s line and neutral connection.
4. Verify that there is no short between the connection for line and neutral on the Relay Box’s outlet during the on and off state.
5. Start Smart Meter Board by plugging it into Mains.
6. Start IHD430.
7. Press S2 pushbutton to put IHD430 in TX mode. A TX should be displayed on the upper-left corner of the screen.
8. Start GUI by opening and running the MSP430GUI project located in the \MSP430GUI\MSP430GUI path in the GUI Code download.
9. Press the Start Energy button on the GUI.
10. Turn on the End Device in the Relay Box.
11. Toggle through the different Chronos options by pressing the # button on the Chronos Watch until “EnrGy” is selected.
12. Select the Energy option by pressing the down button on the Chronos Watch.
13. Wait until the first line of the Chronos Watch is replaced with either “MAN” or the trigger power.
Demo Cleanup Steps—Perform these sequence of steps after each demo:
1. Press the Disconnect button on the GUI, which should disconnect the watch from the Energy option.
2. Exit out of the GUI.
3. Disconnect the SMB from Mains.
4. Turn off the End Device in the Relay Box.
5. Turn off IHD430.
6. Disconnect all remaining physical connections.
EZ430-RF2500 Code: http://processors.wiki.ti.com/index.php/File:EZ430-RF2500_Code.zip
Chronos Watch Code: http://processors.wiki.ti.com/index.php/File:Chronos_Watch_Code.zip
The above project is a simple and elegant way to monitor and control energy delivered. The presence of manual and automatic modes helps the customer or the utility company to constantly monitor power consumption. Think of this “smart meter-relay combo” in every plug in your home or office and in every appliance in your home. Remote monitoring helps in centralized load management in a home or business. Remote disconnect helps in energy conservation, power management and appliance protection. The bridge between sub 1 GHz and 2.4 GHz will almost always be necessary. For example, commands from a utility company can be sent at Sub 1-GHz thorough Wide Area Network (WAN) and communication between the various smart appliances in a home will be at 2.4 GHz through the Home Area Network(HAN).
I would like to give a special thanks to Kripa Venkat and the rest of TI’s Metering Business Unit for their insight and direction during this project. I would also like to thank Adrian Fernandez of MSP430 Marketing for helping me shoot the video. In addition, I would like to thank Professor Anderson and Professor McClellan for the opportunity to first work with the MSP430. Finally, I would like to thank Georgia Tech’s James Steinberg and Edgar Jones for helping me build the relay box.