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AC Phase, Neutral, Earth Fault Indicator Circuit

Last Updated on July 30, 2019 by Swagatam 22 Comments

The circuit explained here will provide LED indications and show if there's a possible fault in the wiring of your home AC Phase, Neutral, and Earth connections. The idea was requested by Mr. SS kopparthy.

Table of Contents
  • Technical Specifications
  • Using 3 LEDs for the Indications
  • Simplified Schematic

Technical Specifications

sir, very good morning. I thank you for your help. I further wanted you to consider a circuit whose pics are attached with links given.

This pcb would indicate me when earth is leaking(at that time the tester would burn when touched to earthing pin in 220v socket and will get a strong shock when touched by mistake.

Even the metal bodies of appliances give shock at that time.) by switching on the first two led's.if you look at the attached pics, you can see that the circuit has only a few resistors and diodes, and a black colored capacitor at back.

i also tried to draw the circuit diagram by seeing that pcb. the same pcb indicates the fuse blown condition.for circuit diagram and pictures of pcb, please see "


sir, i hope you understand the working of circuit and also hope you'll tell how its working to me also.......the purpose of writing this is that i would like you to help me by designing the circuit which has buzzer with led indication when something goes wrong. thank you very very very very very very very very much sir.........i cannot forget your help......

warning message: electricity is dangerous, proceed with caution
earth leakage circuit diagramdrawn by seeing pcb 1
full photo 1
fuse removed... 1
led detail 1
pcb back 1
pcb front 1

Using 3 LEDs for the Indications

The above circuit can be much simplified and implemented using a just three LEDs and some resistors.

The circuit may be understood as follows.

The design of the proposed LIVE or phase, neutral, earth indicator circuit is rather simple.

As can be seen in the given diagram one LED is connected across the phase/neutral, another LED across phase/earth and a third one across neutral/earth.

Each LED has its own limiting resistor rated at 56K 1 watt.

The illuminations from the LEDs in response to the different L/N/E faulty conditions could be witnessed as given under:

LED1 and LED2 ON and LED3 OFF indicates a good overall situation wherein the phase, neutral and earth could be assumed to all wired correctly.

LED2 and LED3 ON and LED1 OFF indicates a wrong polarity of phase/neutral but earth and neutral may be assumed to be rightly configured.

All three LEDs ON indicates an open earth or neutral which may be diagnosed further. Since an open neutral is rare, the possibility of an open "earth" could be considered and investigated.

In addition to the phase, neutral, earth fault indications the circuit also employs a blown fuse indicator in the form of LED4 which simply lights up if the fuse is blown or open and a appliance hooked up.

Note tat the polarity of the LEDs are not crucial and could be used any way round.

Use of red LEDs is recommended, other types could show unusual responses.

The earth leakage sensor and buzzer circuit will be soon updated.

Simplified Schematic

live neutral earth fault indicator circuit 1

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About Swagatam

I am an electronics engineer with over 15 years of hands-on experience. I am passionate about inventing, designing electronic circuits and PCBs, and helping hobbyists bring their projects to life. That is why I founded homemade-circuits.com, a website where I share innovative circuit ideas and tutorials. Have a circuit related question? Leave a comment.... I guarantee a reply!

Previous Post: « Microcontroller Basics Explored
Next Post: Earth Leakage Indicator Circuit for Detecting Current Leakages in Ground Wires »

Reader Interactions

Comments

  1. Sandeep says

    September 25, 2020 at 11:21 am

    Can we get a PCB for assembling the Phase-Earth-Neutral fault indicator circuit?

    Reply
  2. Umesh says

    August 10, 2020 at 12:12 pm

    Hi Swagatam,

    I am working on EMI/RFI filter and Surge suppression circuit for Extension board (230-250 VAC,50 Hz supply) and looking for standard circuit for the same. Can you please send me the optimized PCB circuit and schematic for EMI/RFI filter and Surge suppression circuit?

    Regards,
    Umesh

    Reply
    • Swagatam says

      August 10, 2020 at 5:54 pm

      Hi Umesh, you can try the following circuit:

      comment image" alt="RFI EMI filter with surge supression circuit" />

      Reply
      • Umesh says

        August 10, 2020 at 7:29 pm

        Thank Swagatam for your prompt response. Is it possible to include indicator LED’s for Phase,Neutral and Earth. I am having modified circuit but don’t know if it is right or wrong? I am not able to share image of circuit with you in comment box. Is any other way of sharing circuit?

        Regards,
        Umesh

        Reply
        • Swagatam says

          August 11, 2020 at 1:42 pm

          Umesh, for LED connections you may have to implement the second circuit which is explained in the above article. You can also try your modified design by connecting the L, N. E wires across the relevant lines. You can share the image through Google drive.

          Reply
          • Umesh says

            August 11, 2020 at 6:58 pm

            Hi Swagatam,

            Again Thanks for your response. Based on your circuit details and combining it with LED indications I prepared modified circuit. Please check on following google drive link for comments and let me know if changes required.

            https://drive.google.com/file/d/1KEQghUqLpgeGl9pI4kFfMxBHs85t_orP/view?usp=sharing

            Regards,
            Umesh

            Reply
            • Swagatam says

              August 11, 2020 at 8:27 pm

              Hi Umesh, please change the link to sharing mode so that it becomes accessible to me.

              Reply
            • Umesh says

              August 11, 2020 at 8:45 pm

              Hi Swagatam,

              Please access following link.

              https://drive.google.com/file/d/1KEQghUqLpgeGl9pI4kFfMxBHs85t_orP/view?usp=sharing

              Regards,
              Umesh

              Reply
              • Swagatam says

                August 12, 2020 at 2:33 pm

                Hi Umesh, the LEDs should be on the switch side according to me, as shown below.

                comment image" alt="computer strip board circuit diagram" />

                But the RFI section is not as per my design so I cannot comment on that.

                Reply
  3. Binoj K says

    March 27, 2020 at 10:24 pm

    Hi swagath sir, can you please send me the pcb schematic for the circuit. I was looking for it for quite a long time. And is there any problem for the first given circuit? I have one similar to that but burnt out some way .All the three LEDs and 2 resistors are burnt.

    Reply
    • Swagatam says

      March 28, 2020 at 8:22 am

      Hi Binoj, sorry I do not have a PCB design for this project. use 1 watt wirewound resistors, they won’t burn

      Reply
  4. Aslan says

    November 3, 2017 at 9:29 pm

    Hi dear Swagatam

    I have 3 questions about the first pic circuit :
    1) In which amount of earth resistance, this instrument shows that earth is faulty?
    2) If earth is disconnected, are the other tests (like L&N inverse) possible?
    3) Can this instrument show that earth and ground are connected to each other, inside wall ?(if yes, which fault will be showed ?)
    thank you for your help

    Reply
    • Swagatam says

      November 4, 2017 at 10:58 am

      Aslan, I cannot interpret the first circuit because it is not designed by me, and also because I feel it is not correctly designed.

      Reply
  5. Hamid Gh says

    December 10, 2016 at 2:58 pm

    Hi Mr Swagatam Majumdar

    In my country (Iran) there is no earth and I have circuit that need real phase and null entered , and
    If the reverse were entered ،
    The circuit does not work until the phase and neutral are correct.

    Please guide me

    Reply
    • Swagatam says

      December 11, 2016 at 8:45 am

      Hi Hamid,

      you can use a neon line tester to verify which side was the phase, and then plugin the device with correct polarity.

      I hope I understood your requirement correctly…

      Reply
  6. Unknown says

    February 26, 2016 at 5:17 pm

    What is the reason for C1?

    Reply
    • Swagatam says

      February 27, 2016 at 10:45 am

      It could be an MOV, not a capacitor

      Reply
  7. vivek bhakta says

    October 6, 2014 at 7:41 am

    thankx a lot sir

    Reply
  8. vivek bhakta says

    October 1, 2014 at 1:50 pm

    sir i build this and working fine but my collage sir ask me how i choose 56k resistor i need formula and explanation i mailed u also please reply as soon as possible thankx in advance

    Reply
    • Swagatam says

      October 2, 2014 at 5:14 am

      Vivek, it has been selected arbitrarily such that the LED produces good brightness and also the resistor stays cool…

      although the actual formula is (220V – 3.3)/0.02….this gives around 11k but this value will need to be of 220 x 0.02 = 4.4 watts which can be bulky therefore 56k was chosen so that 1/4 watt could be used.

      Reply
  9. Ahmed Askar says

    May 15, 2014 at 3:15 pm

    hi Swagatam..
    is there any chance to see a circuit of a transformless power inverter like 12/9amps to 220 v or 6v/4 amps to 15v ?

    Reply
    • Swagatam says

      May 17, 2014 at 3:59 am

      Hi Ahmad,
      I'll start publishing them serially as soon as I crack how to design ferrite transformers as per the specific needs without using complex formulas, until then it would be difficult.

      Reply

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