Reverse Polarity LED Circuit (plus more; relays, capacitors, diodes...)

Discussion in 'General Electronics Chat' started by Diff3RentBreed, Sep 17, 2016.

  1. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    To start, I am not an expert with electronics and I lack a lot of the basic skills and knowledge since this is the first major electronic project that I have ever done. So forgive me for not speaking the language but here is my problem:

    I am installing new headlights into my vehicle and I want to customize them. These headlights have halo rings and 4 194 size LEDs at the top. Now I can wire these up normal just fine but I am looking to make a more customized look that no one else has.

    What I want:
    1) Turn off the halos when I turn on my turn signal
    2) Use switchback LEDs so that they will turn amber when I turn the signal on and shine white when it's off

    Troubleshooting:
    I have been working on this project for a week now and I am stumped at how to make this happen.

    Halos:

    I do believe I may have this figured out. What my plan for this is to use a capacitor with a relay so that when I turn on the turn signal, it charges the capacitor and that keeps the relay in the off position long enough for the turn signal's power to kick back on and keep the capacitor charged until I turn off the signal. Do you think that this will work?
    Parts ordered:
    Relay: https://www.amazon.com/gp/product/B017VDI0GY/ref=oh_aui_detailpage_o05_s03?ie=UTF8&psc=1
    Capacitor: https://www.amazon.com/gp/product/B007SVHFXO/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 (I wasn't sure what size I was going to need)
    I thought that I might be able to reverse the polarity (using what's in the next section) to turn it off but these work with the polarity reversed anyway. So that's out.

    LEDs:
    I am trying to wire up switchback LEDs so that when I have the parking lights on, the LEDs will light up white and when I turn my turn signal on, they will light up amber. These are the LEDs that will be purchasing: http://www.autolumination.com/switchback.html#table115. These LEDs work with reverse polarity. "There are only two wires going to this bulb (socket).; One is (+) the other is (-).; The bulb will only switch colors if/when the (+/-) polarity to the bulb is reversed." Which is good because that's how the sockets are on the lights now. The problem I am running into is just that. I do not know how to reverse the polarity and not cause the thing to short out. I am open to anything that will work. The simpler the better in this case. Everything will be wired inside the engine bay right by the headlight so this will be exposed to the elements so protective measures will have to be considered with any option.

    Again, I am far from an expert let alone even a novice when it comes to this stuff. I even have hard times reading wiring schematics and I do not know the symbols. So please bear with me when trying to explain something. But I do highly enjoy these things and I am looking forward to learning more!

    If you need any photos of these headlights, where they are going, the wiring of the headlights, or something else, please, let me know. Both of these end up having just one positive and one negative lead coming out of them (all four LEDs are wired together already).

    Almost forgot to mention, my turn signal has three wires going to it. Ground, Constant 12v, and one that flickers 12v/0v (turn signal). These are what I am looking to use for power and activating power. I can use this for ground (preferably) or ground it to a different bolt.

    Thank you so much for your time and I look forward to hearing from you guys.
     
  2. be80be

    Senior Member

    Jul 5, 2008
    431
    57
    You could do this with the right relay.
    But I would find the right plugs for your car
    So you don't have to cut wires and just plug it all up like it is to the lights.
    You tap off the turn signal.
    Use that to charge big cap that holds relay on. And with a double pole double throw relay you change the leds to amber.
    When the turn signal off it turns them back to the white leds
     
  3. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    So much explaining for just that. Haha. Okay, I will looking into what a double pole double throw relay is. Thank you!
     
  4. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Ya, I'm just not wrapping my head around what needs to be done here. I am still lost and have been looking this up. So I have the halo problem solved then with the capacitor. But I am still not understanding how to reverse the polarity. If it is grounded, wont it always be grounded? I have made up, probably the best diagram that you will lay your eyes on illustrating how I believe I should wire this up and I am just not understanding what to do with the positive and the ground.

    If it's grounded, wont it always be grounded that way? How would I stop that? I mean relays just deal with positive flow, not grounding things. Is that correct?

    And if I connect the single relay to the double relay then that'll mean the double relay is always on and it's not flashing the lights.

    So I am halfway there by being able to shut the lights off but I am super stuck on how to reverse the polarity. I know it must be something simple that I'm just not seeing/understanding but if anyone has any incite. Please help.

    Thanks.
     
    Last edited: Sep 17, 2016
  5. crutschow

    Expert

    Mar 14, 2008
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    Do you want the turn signal to alternate between yellow and white, or between yellow and off?
     
  6. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    I want the led to stay on white until I turn my signal on and then I want it to flash Amber. I'm sorry I was unclear in the first post.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    I only ask because it would be easier to flash amber-white than amber-off
     
  8. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    The only problem with that is amber is the only color that is supposed to be flashing for a signal light. Legality reasons. Which is why I am looking for amber on, amber off while the signal light is engaged.
     
  9. crutschow

    Expert

    Mar 14, 2008
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    Edit:
    Here's a circuit that requires just one DPDT relay.
    I don't know if the LED polarity is correct for the color, so you need to determine that and connect the LED appropriately.
    When the blinker is off the relay is also off and a steady voltage goes to the LED through the NC contacts and respective COM terminals of the relay...
    When the blinker is on, the relay is energized through the diode capacitor circuit.
    This routes the blinker voltage to the LED through the NO contacts and the respective COM terminals with reversed polarity.

    upload_2016-9-18_1-17-53.png
     
    Last edited: Sep 18, 2016
  10. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Okay. I understand this. That does make sense. Awesome! Two concerns though, doing it this way, wouldn't it keep the halos on constantly since that red wires voltage never drops. Secondly, wouldn't this cause the led that will now be amber to not blink since the spot relay will be constantly on due to the capacitor?
     
  11. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Okay. I was looking at your post on my phone. I am now on my computer and see the blinker connected to the no port and you saying it'll make it blink. It makes more sense now that I can read your post and look at the diagram at the same time. Thank you a lot! I can't wait to try this out. Now I have to order the DPDT relay and wait for it since I have no small electronics store around me. :/. I'll update with a success or not. Thank you again! :)

    Although I do still have a concern about the halos always being lit because the voltage of the red wire never goes down. It is always at 12v.
     
    Last edited: Sep 18, 2016
  12. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Okay crutschow. So not being sure if your solution would work completely the way I want it. I kept the 5 pin relay in I had originally so that it will turn off the halos and the power to the led when the turn signal is active. I'm just uncertain that the halos will turn off since you have the constant 12v wire hooked directly to them and this way they will turn off. Then using your method, I added the DPDT relay in to reverse the polarity and make it blink amber. What do you think?
    upload_2016-9-18_10-43-56.png

    As a side note, sorry about the triple post. I am not able to edit those posts because the time frame is up.
     
  13. crutschow

    Expert

    Mar 14, 2008
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    Yes, connecting the red circuit to a steady 12V will leave the lights on all the time.
    But I think the 12V blinker voltage is connected to the ignition switch voltage and goes on and off with that.
    If not, then you need to connect the Halo lights and the top NC contact to whatever you want to use to switch them on and off.
    That could be an added switch or the ignition accessory circuit.

    If all the lights are LEDs, which take a relatively low current, you won't need the SPDT relay.

    And delete the diode between the Halo lights and the turn signal lights. That will generate a short circuit between the COM and NC terminals when the relay is off. :eek:
    The LED is powered through the two NC relay contacts when the blinkers are off, as I showed in my diagram..
    Why did you think that wouldn't work. :confused:
     
    Last edited: Sep 18, 2016
  14. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Because I don't fully understand how the DPDT replay works. So me try to be to understand it, I get things wrong. What I meant by it always being on is that when I turn the key and my lights are on, the 12v connection (red wire) is always 12v. So even when I flip my turn signals on, that 12v is still a constant 12v. Which is why I was including the other relay again to control the halos and have them turn off.

    My concern with your diagram is that when I turn the signals on, the halos will still be lit since they are wired directly to the 12v constant source.

    Looking things over. It looks like I'll be able to do what I want by leaving the relay in and instead of connecting the halos to the leds, I can just use that wire to connect to the top nc port.

    Okay. I think I have got this. I ordered some DPDT relays and I'll be trying this when they come in. Thank you very much!
     
  15. crutschow

    Expert

    Mar 14, 2008
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    Sorry, I missed that you want the Halos off when the blinkers come on.
    In that case just connect the Halo light to the relay as shown.

    That point is positive through the top COM to NC connection to energize the Halo light when the blinker and relay are off.
    It's connected to ground (thus Halo light off) through the NO to COM connection when the blinker is on and relay energized.

    upload_2016-9-18_23-14-43.png
     
    Last edited: Sep 19, 2016
  16. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    That indeed does make sense! Thanks! You're the best. Now I eagerly wait to receive the relays.
     
  17. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Just another question, what size capacitor should I use for this?
     
  18. crutschow

    Expert

    Mar 14, 2008
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    It depends upon the blinker frequency and the relay resistance.
    For a 1 second blinker frequency and a 100Ω relay coil, the capacitor should likely be at least 5000μF (16V).
    You may need to experimentally adjust that value for proper operation.

    Note that you need a good sized diode to handle the surge current of charging that capacitor.
    A 1N400x diode with a 1Ω resistor in series to limit the surge should work.
     
  19. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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  20. Diff3RentBreed

    Thread Starter New Member

    Sep 17, 2016
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    Last edited: Sep 19, 2016
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