In the datasheet of HLW8012, the both 33nF capacitors , 1K resistor and 0.1uF capacitor are connected to GND. I'm not sure where should I connect those ends of components marked with GND symbol, (To Live, To Natural or the DC GND). I can't read Chinese, I don't really know what everything mean there.

Live directly connects to the shunt resistor and this means that live is also GND (0 volt reference) for the chip? Should I connect those end of components marked as GND symbol to Live wire?

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    \$\begingroup\$ Why are you using a chip that has a Chinese Datasheet if you're not able to read Chinese?! \$\endgroup\$ Jun 14, 2019 at 7:52
  • \$\begingroup\$ It is way too cheap , bad thing is the documentation is so poor, and I can't find any information from the internet. And I'm very concerned about safety during testing \$\endgroup\$
    – Khaalidi
    Jun 14, 2019 at 8:07
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    \$\begingroup\$ I don't even understand why you'd need that IC – you've got a fast MCU with a multi-channel differential ADC sitting around anyway. That, and a current transformer or a hall sensor, is all you need for an RMS power meter. Have you researched how power metering is done? \$\endgroup\$ Jun 14, 2019 at 8:15
  • \$\begingroup\$ What I researched about is the IC outputs a pulse of a frequency inversely proportional to the value to be read. This IC provides two PWM outputs, the first one for power and the second one for current or voltage. A 1Hz pulse on CF pin means around 12W RMS. A 1Hz pulse on CF1 pin means 15mA or 0.5V RMS depending on the value in SEL pin \$\endgroup\$
    – Khaalidi
    Jun 14, 2019 at 8:21
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    \$\begingroup\$ not what I meant: You seem to think you need that IC to do a power measurement. However, your arduino already has all the things you need to build a power measurement. Which might be clearer to you if you tried to understand what a power measurement actually is, not in the context of the HLW8012, but in general. \$\endgroup\$ Jun 14, 2019 at 8:24

1 Answer 1


The ground symbol in that schematic refers to a local ground.

You must NOT connect it to mains earth, live or neutral !!!

Do note that this "local ground" of this circuit is NOT ISOLATED, it more or less connects directly to mains live.

So you cannot for example connect this circuit to a PC via USB. That would make the whole chassis of the PC live.

Ideally this circuit would be inside its own plastic box and have no connections to the outside world other than the mains live, neutral and the "measured live" to the load.

The ground of the circuit is then purely local and remains inside that plastic box.

If you have little experience with circuits running directly on mains voltage then study how this is done in other designs.

  • \$\begingroup\$ I'm testing things with Arduino Mega now, by local ground do you mean GND of my Arduino? Should I power on my Arduino from a Battery and the battery GND is my Local Ground? \$\endgroup\$
    – Khaalidi
    Jun 14, 2019 at 7:00
  • \$\begingroup\$ @Khaalidi for example. A battery actually doesn't have any "GND"; it has a positive and negative terminal, and it's pretty common that you connect one of them to local ground, but it's by no means necessary. In your case, it's very likely your battery's negative terminal is connected to the local ground of the arduino (otherwise, there would have to be an isolated SMPS between battery and arduino, which almost certainly is not the case). \$\endgroup\$ Jun 14, 2019 at 7:50
  • \$\begingroup\$ So, to conclude: That "downwards pointing triangle" is just a symbol saying all nets with that triangle should be connected and called "ground". That doesn't say anything whether or not that ground is connected to anything. \$\endgroup\$ Jun 14, 2019 at 7:51
  • \$\begingroup\$ @MarcusMüller github.com/dimitarminchev/HAS8266/blob/master/Hardware/SCH.png Looking into his design, it seems that the AGND connected to Neutral. \$\endgroup\$
    – Khaalidi
    Jun 14, 2019 at 8:01
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    \$\begingroup\$ Your questions about "ground" and this circuit being mains powered leads me to advice you to not proceed with this project until you have more experience. This is AC mains and therefore lethal if implemented incorrectly. You must really know what you're doing. I think that you're not at that level yet. There are safer solutions to measure mains current like using a current transformer. \$\endgroup\$ Jun 14, 2019 at 8:46

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