1
\$\begingroup\$

I came across the following circuit on a random website:

phase neutral earth fault detection circuit

Source website

My guess is this circuit is used by some extension boards as shown below:

extension board

I understand that LED1 current (around 2 mA) is flowing into the earth when things are working fine.

My questions are as follows:

  1. Is this an acceptable practice in general?

  2. Will it cause the RCCB/ELCB to trip, assuming someone is using 20-30 such products (extension boards)?

\$\endgroup\$
4
  • \$\begingroup\$ Actually, the current through the LEDs would be about 230/56 = 4.1 mA. \$\endgroup\$ Commented Feb 21, 2024 at 12:33
  • \$\begingroup\$ @MathKeepsMeBusy - i am considering half pulse only assuming negative pulse won't pass. that's why I am getting half of what you got. \$\endgroup\$ Commented Feb 21, 2024 at 12:40
  • \$\begingroup\$ Yes, I should have taken that into account. Sorry. \$\endgroup\$ Commented Feb 21, 2024 at 12:44
  • \$\begingroup\$ @Whiskeyjack if we are done here, please take note of this: What should I do when someone answers my question. If you are still confused about something then leave a comment to request further clarification. \$\endgroup\$ Commented Nov 6, 2024 at 9:39

1 Answer 1

Reset to default
1
\$\begingroup\$

Is this an acceptable practice in general?

If you mean is the circuit suitable then the answer us a big fat "no". LEDs have a maximum reverse voltage that is at best tens of volts and not hundreds of volts.

Will it cause the RCCB/ELCB to trip, assuming someone is using 20-30 such products

The design is flawed; it will burn first so I'd be more inclined to worry about that than worrying about tripping an RCCB.

\$\endgroup\$
2
  • \$\begingroup\$ Andy, sorry. I just forgot about this. I thought I will circle back to see more comments and answers but that didn't happen. I have some follow up questions. I agree that this is not a good practice but I do see products like these being used by many people. At some point, even I used one of these without any problem. Do you think the current limiting resistors are saving the LEDs even though the voltage is being exceeded? \$\endgroup\$ Commented Nov 6, 2024 at 9:50
  • \$\begingroup\$ The devil is in the detail of the actual LED. If it's a bidirectional LED then it won't matter and could work just fine @Whiskeyjack \$\endgroup\$ Commented Nov 6, 2024 at 10:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.