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Basic AC LED Circuit - help

  1. Oct 3, 2013 #1
    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
     

    Attached Files:

  2. jcsd
  3. Oct 3, 2013 #2

    berkeman

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    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?
     
  4. Oct 3, 2013 #3
    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?
     
  5. Oct 3, 2013 #4

    berkeman

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    What is this used for?
     
  6. Oct 3, 2013 #5
    This is the timer circuit, this may help.

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

    Its designed to do what i'm doing.
     
    Last edited by a moderator: May 6, 2017
  7. Oct 3, 2013 #6
    Its just a simple circuit that turns on a pump. ( .4 amp load )
     
  8. Oct 3, 2013 #7
    OK, I belive 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.
     

    Attached Files:

  9. Oct 3, 2013 #8

    berkeman

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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).
     
  10. Oct 3, 2013 #9

    berkeman

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    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?
     
  11. Oct 3, 2013 #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
     
  12. Oct 3, 2013 #11
    Its an aluminum enclosure. The ground goes to the motor ground and the case but that is not shown in the diagram.
     
  13. Oct 3, 2013 #12

    berkeman

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    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.
     
  14. Oct 3, 2013 #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.
     
  15. Oct 3, 2013 #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??
     

    Attached Files:

  16. Oct 3, 2013 #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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