Energy meter

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  • Note: Power supply of HLW8012 and AC Mian Live and natural should be NOT isolated.
  • Note: Better use optical-coupler to send signal to your MCU, this make it isolated. MCU shared power supply with HLW8012 is not a good idea.

Power supply of HLW8012

  • More non-isoated power module refer to AC-DC

In order to match the resistance sampling method (ie, direct sampling signal from the grid, non-isolated), the power supply circuit must be non-isolated power supply, non-isolated power supply in two ways: AC-DC non-isolated power supply, The comparison is as follows:

  • LNK304 designed AC-DC non-isolated power supply

The use of LNK304 designed AC-DC non-isolated power supply, L and N, respectively, is the AC line and the zero line to zero line as a ground. This circuit does not need transformer, regulator 5V, can provide about 150mA current, to ensure that AC85V ~ 265V AC range, to achieve a stable voltage output, ripple is also very small, about 50mV. This power supply provides operating voltage for all modules.

  • Resistive buck power supply

After the regulator capacitor C1 step-down, the diode rectifier, the use of 1N4749 power down to 24V, and then through the regulator chip 78L05 output power stabilized at 5V, to provide power to the HLW8012, 24V for driving the relay. If the choice of 12V relay, then 1N4749 need to be changed to 1N4742, but the safety capacitor C1 need to be changed to 1uF capacitor to improve the drive current.

HLW8012 Pin Definition

  • High-frequency pulse CF, indicating active power, in the range of 1000: 1 to achieve ± 0.3% accuracy
  • High frequency pulse CF1, indicating current or voltage rms, using SEL selection, ± 0.5% accuracy in the 500: 1 range
  • Built-in crystal, 2.43V voltage reference source and power monitoring circuit
  • 5V single power supply, operating current less than 3mA


HLW8012 calibration.png
  • Fcf = Power, Fcf1 = current, Fcfu = voltage
  • V1: Voltage signal on the current channel pin
  • V2: Voltage signal on voltage channel pin
  • Fosc: built-in crystal, the typical frequency of about 3.579MHz;
  • Vref: built-in reference source, the typical voltage is 2.43V

Use with ESP8266

  • Download demo code from our github
  • The demo code will monitoring the power, current, voltage and frequency, you can monitor it via telnet to see remote debug output, same as serial output, but safe when AC main power connected.
  • Pin definition to esp8266 please see the comments in sketch
  • Also can calibrate the parameters, see the comments in sketch
  • Enter SSID and password in the sketch, run the demo code first to see IP address
  • Connect to AC main power, login remotely via telnet, in windows for example, command: telnet






  • Demo -1: on board sample resistor is 0.002R, 2mR, diameter 2.5mm, rate current is 20A. space is 10mm, height 7.5mm, "door" shape.
  • Demo -2 PCB File


Other Reference

Demo Code ESP8266

Demo Code STM32


Energy monitor ICs:

  • ATT7309
  • ADE7758
  • 锰铜取样电阻
  • CS5460