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  1. #1
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    How to run LEDís at different currents from one driver.

    I have had this idea going on in my head for ages. It is a light based on this flash gun.



    I want to have 2 LEDís with DNA optics at the top running at 1A (for example) and 1 LED at the bottom running at 400 ish mA with just a frosted cover to add a bit of close up light.

    Can it be done running them all from the same buck driver? How would it be wired?

    Thanks

  2. #2
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    from 1 buck driver, I dunno, but I've read about people running multiple LEDs at different currents from AMC7135 based drivers. It either involves cutting traces and wiring up individual (or multiples of) 7135 chips or some fancy ATiny chip programming that I won't pretend to understand. Not sure if that helps though

  3. #3
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    Thanks Matt.
    That's why the idea has been I my head for ages

  4. #4
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    It's doable but really really inefficient. You can wire the 1A pair in series and parallel to them the 400mA one with a resistor, or you could wire them all parallel and use a resistor again for the 400mA LED. Assuming all the LEDs are the same at least if not from the same batch when all wired in parallel.

    Or like Matt suggested using AMC7135 based drivers or even single chips to limit the current.

  5. #5
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    Thanks Toaster. That was the only way that I could come up with and it is just a waste of juice.
    May as well run all three at the same current rather than use resistors.

    Never mind it saves me having to make the housing.

  6. #6
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    I would wire them at the same current setup anyway since the one behind the diffuser will be nothing but a wall of light.

  7. #7
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    The plan was to have the bottom light reflected down by the longer top so as not to be a wall of light but only a low output so as not to be too bright right in front of the bike.

    Just like in my grubby old drawing. Probably a daft idea anyway.
    Attached Thumbnails Attached Thumbnails How to run LEDís at different currents from one driver.-grubby.jpg  

    Last edited by yetibetty; 11-20-2012 at 05:00 PM.

  8. #8
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    Did you consider using eliptical optics for the bottom one. It would give you wide horizontal spread of the light and wouldn't compromise your vision as a wall of light, neither mess with your high beam.

  9. #9
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    I think the simplest way to achieve this would be to wire it like Trouties SpiderEyes. Two LEDs on the top in series and two below parallel to get half the current each from the driver.

    He uses XM-L at the top and and XP-G below but there's nothing stopping you using 4 XP-Gs.

    You could have the top two at 1A with the LED-DNA optics and the bottom two at 0.5A with the Carclo 10417 10mm optics below - the ones I used in the Picasso light. You will need to have the bottom XP-Gs on 10mm boards by the way if you are going to use those optics.

    I'm ordering some of those Carclo optics soon from DigiKey yeti, let me know if you want to add to that order.

  10. #10
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    I went the Lowes route and use a led miniature spotlight wired to two 18 volt drill batteries, great light and 5 hr run time,..

  11. #11
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    Thanks to all for the replies. But as it's never going to be how I planned I'll put the idea on hold and plan something different.

  12. #12
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    One word for the effect you are after

    Liberator a d use those free lumens

  13. #13
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    What about using a low bin (Q4) for the lower LED and top bins for the uppers? Run them in a 3S setup at 1A.

  14. #14
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    Yetibetty, I wanted to do the exact same thing, so I used two Lux-rc modules. I used one outdoor tint XP-E 10 watt master (momentary button control), hooked up to a neutral tint 6.5 watt Samsung 3535 slave. I currently use carclo triple narrow optics for both, but bought extra optics (medium and elliptical) to experiment with.

    So far, it's my favorite light. It uses half the power of my previous lights and can run twice as long. The XPE is a good thrower and requires more power (1A @ 875 lumens ), while the Samsung 3535 doesn't need as much power (0.65 A @ 729 lumens) and has a little bit wider beam, which fills in the area the XPE doesn't reach in front of the bike and to the sides. .

  15. #15
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    Quote Originally Posted by annarocco39 View Post
    How would it be wired?



    This is very simple, very easy. Each light engine has it's own driver built in. This setup would require that you use good quality 18650 3.7V batteries. At a minimum you'd need 4 batteries wired 2S2P for a total voltage for the pack of 7.4 V.

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