SLAA494B May   2011  – September 2023 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253

 

  1.   1
  2.   Implementation of a Single-Phase Electronic Watt-Hour Meter Using the MSP430AFE2xx
  3. 1 Trademarks
  4. 2 Introduction
  5. 3 Block Diagram
  6. 4 Hardware Implementation
    1. 4.1 Power Supply
      1. 4.1.1 Resistor Capacitor (RC) Power Supply
      2. 4.1.2 Switching-Based Power Supply
    2. 4.2 Analog Inputs
      1. 4.2.1 Voltage Inputs
      2. 4.2.2 Current Inputs
  7. 5 Software Implementation
    1. 5.1 Peripherals Setup
      1. 5.1.1 SD24 Setup
    2. 5.2 Foreground Process
      1. 5.2.1 Formulas
        1. 5.2.1.1 Voltage and Current
        2. 5.2.1.2 Power and Energy
    3. 5.3 The Background Process
      1. 5.3.1 Voltage and Current Signals
      2. 5.3.2 Phase Compensation
      3. 5.3.3 Frequency Measurement and Cycle Tracking
      4. 5.3.4 LED Pulse Generation
    4. 5.4 Energy Meter Configuration
  8. 6 Energy Meter Demo
    1. 6.1 EVM Overview
      1. 6.1.1 Connections to the Test Setup or AC Voltages
      2. 6.1.2 Power Supply Options
    2. 6.2 Loading the Example Code
      1. 6.2.1 Opening the Project
  9. 7 Results
    1. 7.1 Viewing Results on PC
    2. 7.2 Viewing Results During Debug
  10. 8 Important Notes
  11. 9 Schematics
  12. 10References
  13. 11Revision History

4.1.1 Resistor Capacitor (RC) Power Supply

Figure 4-1 shows a simple capacitor power supply for a single output voltage of 3.3 V directly from the mains voltage of 110/220 VRMS alternating current (ac).

GUID-F58AA4C9-9A9A-41B0-98F5-10F3663B7813-low.gif Figure 4-1 A Simple Capacitive Power Supply for the MSP430 Energy Meter

Appropriate values of resistor R22 and capacitor C49 are chosen based on the required output current drive of the power supply. Voltage from the mains is fed directly to an RC-based circuit followed by rectification circuitry to provide a direct current (dc) voltage for the operation of the MSP430. This dc voltage is regulated to 3.3 V for full-speed operation of the MSP430. For the circuit in Figure 4-1, the approximate drive provided approximately 12 mA. If additional drive is required, either an NPN output buffer or a transformer-/switching-based power supply may be used.