Troubleshooting AC LED Circuit Design: Understanding Load vs Neutral

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Discussion Overview

The discussion revolves around troubleshooting an AC LED circuit design, focusing on issues related to LED behavior when power is applied or removed, and the understanding of load versus neutral connections in AC circuits. Participants explore circuit design challenges, safety concerns, and potential solutions.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant describes a circuit where an LED glows dimly when AC voltage is removed and pulses with the electric motor's stator rotation, indicating a potential design flaw.
  • Another participant expresses concern about the safety of the circuit design, questioning the experience level of the original poster and highlighting wiring errors that could lead to shock hazards.
  • Some participants suggest using a diode to address the LED issue but express uncertainty about the correct wiring and effectiveness of this solution.
  • There is a discussion about the importance of correctly identifying load and neutral connections, with one participant noting that changing the connections improved safety compliance.
  • One participant mentions the need for a fuse in the circuit and the importance of grounding, while another acknowledges the omission of the fuse in their design.
  • Participants share links to timer modules and diagrams, with some expressing a preference for using pre-packaged solutions for safety reasons.
  • There is a mention of a specific LED component and its suitability for the application, along with a question about incorporating a back protection diode to prevent feedback.
  • One participant reflects on their understanding of the circuit and expresses doubt about their fit in the forum, indicating a feeling of inadequacy in the technical discussion.

Areas of Agreement / Disagreement

Participants express a mix of agreement on the need for safety measures, such as fuses and proper grounding, while disagreements remain regarding the effectiveness of proposed solutions for the LED issue and the overall circuit design. The discussion does not reach a consensus on the best approach to resolve the LED behavior.

Contextual Notes

Participants highlight limitations in the original circuit design, including missing components like fuses and grounding issues. There are unresolved questions about the proper wiring of the diode and the implications of load versus neutral connections.

Docotrj
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I really don't know much about circuit design, but I have built a device and it requires a LED indicator when power is applied to the load.

I also need a very low parts count.

The Problem. As I have designed it the LED glows ever so dimly when ac voltage is removed and when power is removed and electric motor spins down the LED pulse with the stator rotation.

I thought I could simply add a 1N4007 diode to fix the problem, but after a failed attempt I'm not sure how to wire it in or if I don't understand the solution.

The second problem is I don't understand about load vs neutral on the AC receptacle does it make a difference how i hook it up based on my diagram attached?

Thanks so much in advance for anyones help.

Shane

PDF of electrical diagram attached
 

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Docotrj said:
I really don't know much about circuit design, but I have built a device and it requires a LED indicator when power is applied to the load.

I also need a very low parts count.

The Problem. As I have designed it the LED glows ever so dimly when ac voltage is removed and when power is removed and electric motor spins down the LED pulse with the stator rotation.

I thought I could simply add a 1N4007 diode to fix the problem, but after a failed attempt I'm not sure how to wire it in or if I don't understand the solution.

The second problem is I don't understand about load vs neutral on the AC receptacle does it make a difference how i hook it up based on my diagram attached?

Thanks so much in advance for anyones help.

Shane

PDF of electrical diagram attached

Welcome to the PF.

There are wiring errors in your circuit that make it quite dangerous (shock hazard mainly). Why are you making this if you have very little electrical design experience, and probably no experience working with AC Mains connected circuits?
 
Thank you for your reply, well to answer your question because I have to, no one will do it for me and I have learned by doing all my life.

Can you help me fix the circuit?
 
Docotrj said:
Thank you for your reply, well to answer your question because I have to, no one will do it for me and I have learned by doing all my life.

Can you help me fix the circuit?

What is this used for?
 
This is the timer circuit, this may help.

http://new.grainger.com/product/DAYTON-Time-Delay-Relay-6A859

Its designed to do what I'm doing.
 
Last edited by a moderator:
berkeman said:
What is this used for?

Its just a simple circuit that turns on a pump. ( .4 amp load )
 
OK, I believe I corrected what you may be concerned about. Also let me say that the circuit works with the exception of the LED issue I spoke of.
 

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I'm not sure I'm comfortable advising you how to wire this up with bare AC Mains wiring. Given your lack of electrical knowledge so far, it will be pretty dangerous for you to do that. And discussing dangerous activities is against the PF rules, for pretty obvious reasons.

Having said that, it's pretty easy to use Google to find examples of how to do basic wiring with it:

http://waterheatertimer.org/How-to-wire-Dayton-Off-Delay-Timer.html

But, that doesn't show how to handle the Earth ground wire from your AC Mains power cable, it doesn't show how to fuse the system, etc. And it's better to use a small neon bulb rather than waste lots of power in a voltage-dropping resistor for an LED. That diagram is meant more for electrican-level folks to use, not beginners who don't know what-all needs to go around it.

It would be *much* better if you just used a pre-packaged timer module. One that has a captured AC Mains power cord for the input, and a female AC Mains receptacle for the output. Have you looked at them? They are pretty simple to use, and have already earned UL safety approvals (very important).
 
Docotrj said:
OK, I believe I corrected what you may be concerned about. Also let me say that the circuit works with the exception of the LED issue I spoke of.

You changed Hot and Neutral so that Hot goes through the switch, which is correct and required by electrical safety codes. But you still show no fuse, and the grounding is not correct. What kind of enclosure are you using?
 
  • #10
Thanks again. I understand your concerns and thanks for your advise. My diagram matches the circuit you provided.

I had just colored wrong the diagram. Take care
 
  • #11
berkeman said:
You changed Hot and Neutral so that Hot goes through the switch, which is correct and required by electrical safety codes. But you still show no fuse, and the grounding is not correct. What kind of enclosure are you using?

Its an aluminum enclosure. The ground goes to the motor ground and the case but that is not shown in the diagram.
 
  • #12
Docotrj said:
Its an aluminum enclosure. The ground goes to the motor ground and the case but that is not shown in the diagram.

You at least need to have a fuse in series with the Hot lead, right where it enters your grounded aluminum enclosure. That is also required by electrical safety codes.
 
  • #13
I am ordering it as we speak from digikey, I feel silly, I was going to omit the fuse.

I can't thank you enough.
 
  • #14
OK, here is a proper diagram.

Now, I totally understand your argument for a non-LED but my application needs this form factor.

http://www.digikey.com/product-detail/en/Q8P3BXXHR110E/679-2965-ND/3153116

lop is only 6ma, on my circuit this seems reasonable and its only on for a minute at a time.

My original question was incorporating the back protection diode. And stopping the feedback?

http://www.eleccircuit.com/mains-voltage-indicator-with-a-led/

This diagram seems to be the solution but... something does not make sense to me about it. Its like a direct short??
 

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  • #15
I think I answered my own question, because I had the hot coming into the rely where the neutral should have been this caused the light to glow? Soon I will see.

I now understand the neutral and HOT position in the wall socket and the case socket for encloser, seems the right side is HOT all the way through. I think this forum is not for me but i sure appreciate your help. I understand the forum is for experienced trained individuals now so I will go away. take care!
 

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