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Thread: Driving an LED on a Primary CR123

  1. #1
    sween1911's Avatar
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    Default Driving an LED on a Primary CR123

    Hello!

    I have an application that requires using a single primary CR123 to drive an XP-L. 17mm driver size required.

    Most drivers start at 3V for a lower voltage range, optimized for Li-ions but just out of reach of a primary.

    I'm looking into these two from Mountain Electronics as the voltage range starts at 2.5v and has all the other
    features I want. Concerned though because it appears they all have low-voltage cutoffs that will start stepping down.

    http://www.mtnelectronics.com/index....product_id=663

    http://www.mtnelectronics.com/index....product_id=715

    These are about as close as I can get, anyone recommend a better driver for this application?


    Thanks!
    - Joe
    Last edited by sween1911; 05-21-2020 at 03:05 PM.
    Dean Venture: "I'll get the flashlights!"
    Hank Venture: "And I'll get the astronaut Ice Cream!"

  2. #2
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Driving an XP-L on a Primary CR123

    None of them will work for your project!
    The voltage of primary CR123 is below the voltage needed to drive cree XP-L at reasonable power.
    If you are fixed on a single primary CR123, you will need a buck-boost driver.
    But on the other hand there is a mismatch between the power range of XP-L (up to 10W) and a single primary CR123 which is fine for lower power levels only.

  3. #3
    sween1911's Avatar
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    Default Re: Driving an XP-L on a Primary CR123

    Tobias,

    Got it, thanks!

    If I used an LED that needed less current, like an XP-G2, I assume I'd still need to use a boost, like the kind from a 2AA light?

    Any good sources you guys like for that size driver?
    Dean Venture: "I'll get the flashlights!"
    Hank Venture: "And I'll get the astronaut Ice Cream!"

  4. #4
    Flashaholic
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    Default Re: Driving an XP-L on a Primary CR123

    Will be hard to find such drivers. You could try boost only driver but if Vf is lower than battery it would be basically like connecting battery directly to LED.
    Some boost drivers:
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board



    What are you trying to do? How much light do you need?
    Maybe just use something like TerraLUX Maglite AA upgrade module, just connect 3V battery to it and you good.

  5. #5
    sween1911's Avatar
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    Default Re: Driving an XP-L on a Primary CR123

    Quote Originally Posted by arek98 View Post
    Will be hard to find such drivers. You could try boost only driver but if Vf is lower than battery it would be basically like connecting battery directly to LED.
    Some boost drivers:
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board
    http://kaidomain.com/Circuit-Board-D...-Circuit-Board



    What are you trying to do? How much light do you need?
    Maybe just use something like TerraLUX Maglite AA upgrade module, just connect 3V battery to it and you good.
    Here’s my goal: I have a customer with a single-cell flashlight that had a 17mm board and a 16mm XPL and they want to use a primary CR123.
    Dean Venture: "I'll get the flashlights!"
    Hank Venture: "And I'll get the astronaut Ice Cream!"

  6. #6
    Flashaholic*
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    Default Re: Driving an XP-L on a Primary CR123

    With a CR123 primary and an XP-G2, just a simple resistor can be used instead of a driver for a single brightness flashlight.

    I used to build similar ones using LEDs in the past.

    If you like, I can look around and see if I still have some of the high power / 2 ohm resistors around. I think they were a 1206 or something in that size range. I had some special ones made in AlN that are remarkably good at heat dissipation.

    They are about 2x3mm so fairly small if you can work in that size range.

    Lumileds also makes a ton of LEDs in the sub 3 volt Vf range.
    Last edited by HarryN; 05-22-2020 at 11:24 PM.
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