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  1. #1
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    Triple P4 problem

    A colleague has built a light for me with 3 Seoul P4 LEDs and a 3023 Buckpack. It runs off a pack of 12 NiMh AA cells which is about 16 volts. The LEDs are well gunked onto a big heatsink. There's a switch to choose one LED or three.

    It worked well and I'm impressed with it. But the 3 LED option stopped working, and there's a broken wire inside. It's not immediately obvious where it broke from, although I think I've worked it out. I can't contact the guy who built it for 2 weeks, so I'm looking for help here.

    The switch is a single pole, off in the middle, one contact each side. The buckpack +ve feeds the switch. The first contact has a wire to the single LED, which is then connected to the buckpack -ve. The other switch contact goes to the two remaining LEDs in series, and then to the broken wire.

    My assumption is that the broken wire should go to the first contact on the switch. So with the switch on the first contact, one LED is in circuit, the other two are open circuit. With the switch on the second contact, current flows through the two in series, to the other contact (which is open) and on through the single LED, ie, 3 LEDs in series. The LED polarities are all the right way for this. It all seems reasonable, and there's nowhere else I can see that the broken wire could possibly go. So I soldered it on there.

    Problem is, the 3 LED setting doesn't work now. I've checked all the wires for continuity, and there are no breaks, the switch is making contact and my soldering's OK. The single LED setting works normally, ie, the Buckpack seems to be working - it's dropping 16V down to 3.7V or so on a single LED, so why can't I get 11volts ish through the 3 of them?

    Any ideas? What can I try, to diagnose the problem?

    Thanks, Chris

  2. #2
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    Pictures would help. I need to be able to see things to make sense of them.

  3. #3
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    Good point, thanks. (sorry for the pause while I drew it)



    When the switch is at A, the LED with red wire lights. When it was at B, they all used to light.

    Where it's shown dotted, the blue wire is broken off from where it was soldered to. Obviously, the two LED on the blue wire didn't light. I think it should go where the dotted blue line is, ie, join the red wire at the switch. I've soldered it there, but the two LEDs on the blue wire still don't work.

    For anyone reading this post first, full details are in the original post above.

    Where have I gone wrong?

    Thanks, Chris

  4. #4
    fuggansonofahowa
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    Do you lose all LED's when you switch to triple mode?

  5. #5
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    Quote Originally Posted by Hawseman
    Do you lose all LED's when you switch to triple mode?
    Yes.

  6. #6
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    The blue wire should be connected to the same side of the switch as the red wire from the 1st LED (for best results solder the two wires together). If this is what you have done, then it should work.
    Alternatively, you could connect the blue wire directly to one of the negative terminals on the first LED.

  7. #7
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    Quote Originally Posted by dsut4392
    If this is what you have done, then it should work.
    Thanks - at least my logic's OK.

    But I have done that, and it doesn't work.

    The only thing I can think of is that one of the LEDs isn't passing current. Maybe I need to unsolder the leads off the LEDs and test them one by one, but that may not be easy now they're glued to the heatsink.

  8. #8
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    If you have a multimeter with a diode-testing mode ("beep" when there's contact) it should be easy to test both LEDs. You just need access to the pos and neg on each led. Then you won't have to take off the LEDs unless one is actually broken.

    On a side note: if you have a buckpuck with dimming capabilities, I would have used the switch to control the dimming via the buckpuck instead of the way it is now.
    This way the "off" in the middle will give you 100%, and the two "on's" on each side can be configured to dim down to the level you want by using different resistance values between the Ctrl and Ref pins. E.g. climbing mode(50%?) and map-reading mode(10%?). I've done this on my headlight and it works like a charm.
    This way your battery will last longer when dimmed, and you get the same beam pattern on all light levels (if you have different lenses, that is).

  9. #9
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    Thanks, langen.

    I didn't know some multimeters have a diode mode - my usual one doesn't. Some searching turned up one that does, and I now know that I have two totally dead LEDs.

    The broken wire must have touched something - maybe the incoming 16 volts contact?

    My Buckpack doesn't have dimming capability - but it's on my list for the light I'm going to build now.

    How easy is it to remove LEDs from heat conduction epoxy?

  10. #10
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    Bummer with the dead LEDs.. Just remember that diodes conduct current only one way!

    I haven't worked much with thermal epoxy before, but I imagine that you will have a hard time removing them. Hopefully I'm wrong

  11. #11
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    you sure both led's are dead? If one of your leads or wires on any of the led's are not on good then they are not going to work just like the broken wire. It would kinda suck if they both went dead. But good news is they are less than 6 bucks from deal extreme so it looks like if that's the case it will only cost you 12 bucks to get back up and running. But you might want to wait for your friend to come back to see if he will fix them as it will take probably over 2 weeks to get your order from deal extreme.

  12. #12
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    I'm not sure I would trust my friends capabilities for building these circuits either since this is the way he wired the thing. For dimming I would have used the Ctrl./Ref. pins with a 1.2k resistor and a switch. Buddy, you don't need to buy another buck drive with dimming. Just read the data sheets on the Luxeon Buckpuck Drivers and you'll achieve a much better cicuit. Get a meter with a diode testor to check the leds that don't work. They sould light up with a very faint dim amount of light when contact is made with the meter. If you rebuild/ repair this light in the same fashion as your friend built it you're probably looking at all the LED's burning out while running on high down the road. It sounds like there is some improper heating or something going on too. Can you post any pics of this build?

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