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Thread: 3x rebel leds: driver question

  1. #1

    Default 3x rebel leds: driver question

    Hello everyone, First post!

    Im building a drop in module for an old bike light have with some rebel LXML-PWC1-0100 (100 lumens, 350ma, 3v, 1w)

    Now my question is, I was wondering what were some of your suggestions for drivers to run 3 of these rebels. They will be ran off of 3x Ultra Fire 10440 3.6+v (10.8+v) I would like at least 2 modes (high, strobe) but ideally id want a low setting as well. Also Id like to know your suggestion on suppliers. Im tired of oversea orders

    thanks in advance!

  2. #2
    Flashaholic* AnAppleSnail's Avatar
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    Default Re: 3x rebel leds: driver question

    Ultrafire 10440s are unprotected, right? Make sure your driver won't suck them down below a safe voltage of (7.5v).

    Do you want to roll your own? You have the headroom to make a LM317 constant-current driver (Not great efficiency but easy to build). If you do this design then REMEMBER that you are wired to Vadj, not Vout. This will not allow strobe though.

    Buying in-US, hrm. LEDSupply maybe?
    My biggest light-hog is my camera.

  3. #3

    Default Re: 3x rebel leds: driver question

    some of the ultrafire 10440s are protected, the ones im looking at specifically is. im not opposed to building my own driver if it works decently, and thats a pretty interesting design.

    im trying to understand what i need. ok so if my input V is 10.8v and i need it be at 3v @350ma i need a 5.6 ohm 3w resistor?

    thanks for your help.

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    Flashaholic* AnAppleSnail's Avatar
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    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    im trying to understand what i need. ok so if my input V is 10.8v and i need it be at 3v @350ma i need a 5.6 ohm 3w resistor?

    thanks for your help.
    Oh, I thought you were powering all 3 rebels from this pack. In general you want Vbatt to be close to Vled. In this 1-LED case, put them in parallel, or, better, get an 18650. Then you can get by with a smaller resistor, but LED 'resistor calculators' don't work very well. I actually suggest getting some 1W 1-ohm resistors and starting with 5 in series, measure current, then 4...
    My biggest light-hog is my camera.

  5. #5

    Default Re: 3x rebel leds: driver question

    With a 4.2v input the amc7135 driver may work ok here. Here's a list of drivers that may fit your needs. And as AnAppleSnail said your battery configuration will determine your voltage either 12.6v in series or 4.2 in parallel. The 18650 seems like a good idea to me too if your host will allow it.

  6. #6

    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by AnAppleSnail View Post
    Oh, I thought you were powering all 3 rebels from this pack. In general you want Vbatt to be close to Vled. In this 1-LED case, put them in parallel, or, better, get an 18650. Then you can get by with a smaller resistor, but LED 'resistor calculators' don't work very well. I actually suggest getting some 1W 1-ohm resistors and starting with 5 in series, measure current, then 4...
    oh i may have confused something here, i do intend on running all 3 leds in series, and im am limited to running AAA sized batteries.

    thanks

  7. #7
    Enlightened
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    Default Re: 3x rebel leds: driver question

    As the battery voltage is close to the Vf of the leds, a linear reg would be ideal. The amc based circuits are out because the battery voltage is too high (max 6v).

    It may seem like over-kill, but an Lflex driver from Taskled might be just what you are looking for: made in USA, strobe modes, adjustable current levels, battery voltage monitoring....

  8. #8
    Flashaholic* AnAppleSnail's Avatar
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    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    oh i may have confused something here, i do intend on running all 3 leds in series, and im am limited to running AAA sized batteries.

    thanks
    Okay, then you'll want LED and batteries both in series. That LM317 circuit won't play nicely with a strobe mode unless you work a 555 timer in to blink the CC source.

    1.25V / R = I
    1.25V / R = 0.35
    1.25 / (R*0.35) = 1
    1.25 / 0.35 = R
    3.57 ohms ideal, or 4 ohms gives you 312.5 mA which is not very different.

    The other option is to pursue American driver manufacturers. There aren't many PCB makers in the states, but there are some.
    My biggest light-hog is my camera.

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    Flashaholic* VegasF6's Avatar
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    Default Re: 3x rebel leds: driver question


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    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    oh i may have confused something here, i do intend on running all 3 leds in series, and im am limited to running AAA sized batteries.

    thanks
    you really need more than 3 cells to run 3x leds in series, fully charged might look enough, but under load, after some time working voltage of 3 cells will be almost identical to vf of the led, and any driver that isn't leniar needs usually 2v extra to work.
    task led sells good drivers, us based company. b2flex looks like what you might use, but you'll need 1 more cell, unless you wire leds in direct drive , with 3 mode switch (dx\kd stuff) with 2 resistors for modes, you can't really get reliable long operation. from just 3 aaa sized leds.

  11. #11

    Default Re: 3x rebel leds: driver question

    AMC7135 driver will not work with all three wired in series. Unless you do this and it seems you dont have the space needed. Three batteries will work also if wired parallel. They are a few drivers in my other post above in the link, that could meet your criteria.

  12. #12

    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by VegasF6 View Post
    that would also work, but you need to add a resistor to 2 leds before driver, the set up is for p7 they have higher vf, 0,3ohm should be good enough, for rebels.
    however he'll need to remove all but one amc 7135 chips, to get desired 350ma, and unsoldering any component from these boards is very tricky, you heat up the contacts of the part you want to remove, other parts next to it, on the other side of the board, smaller parts, fall off before your part melted the solder.

  13. #13
    Flashaholic* VegasF6's Avatar
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    Default Re: 3x rebel leds: driver question

    Perhaps.
    You can expect a typical 3V dropout from the leds while sinking 350mA. So the first 2 leds should drop 6V combined from the total voltage. Fully charged, the 3 batteries may output 12.6V when brand new, probably less with a little age. At a 1C draw you can expect the battery voltage to sag below 4V per cell almost immediately. Now with 12V supply and 6V dropped you are easily within the capability of the AMC7135 IC. While it has a recommended supply voltage of 6V it has a maximum rating of up to 7V. They are very tough ICs and I have heard of cases where people have heated them up to the point they melted solder and slid off the boards. Up till that point they continued to work as expected.

    Worst case scenario, and I doubt it, but if the supply voltage still isn't in spec, you can add a Schottky diode in series with the VDD pin only to drop ~.3V
    Or better still, run them at 700mA, more light and increase the forward voltage to 3.20V. Maybe the design wouldn't allow for that much heatsinking though.

    As to removing the ICs I didn't literally mean use those boards. There are AMC7135 bases drivers available preconfigured for 350mA or 700mA either one. Though, it is simple enough to harvest the extra ICs for future use, as many of us did before illumination supply started selling them.

  14. #14

    Default Re: 3x rebel leds: driver question

    amc chips have temp protection build in, i have never had one heat up to the point of falling off, they dim and start to blink way before.
    there are 1-2 amc boards, but i have not seen those with pwm chip installed, op asked for multimode.

  15. #15
    Flashaholic* VegasF6's Avatar
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    Default Re: 3x rebel leds: driver question

    Yes, especially from a domestic source. I suppose if I were doing it I would order a 1amp version from shining beam (3 mode) or illumination supply (3 mode) or e-lectronics.net (2 mode) and remove the chips myself. I might look at this thread for pointers. Since my main concern would be lowering the output from my driver and not so much salvaging the chips themselves I wouldn't be so concerned to what happened to them. Why, I might even decide to simply snip the leads with my dykes and manhandle the extra 7135 ICs out of my way.

    Of course, I am not the one doing it. Instead, Evil-98 is the one asking. So, if you are still reading, how about some feedback if any of these ideas will suit you?

  16. #16

    Default Re: 3x rebel leds: driver question

    sorry for the late reply, this is a lot of information to take in and im slowly digesting it. over all it seems there is no "easy" option.



    this interests me, mostly because i have a 8x7135 driver. also on the batteries, i guess i dont have to run the battery internally and run a 4x parallel 18650 pack. will this work? http://www.lightmalls.com/amc7135-8-...-board-for-muc

    edit:

    ok from my understanding is each 7135 supplies 3.5v of 350ma, 3x350=1050ma so i need 3x 7135 chips? so could i just buy a 1050ma 7135 driver puck?
    Last edited by evil-98; 03-05-2012 at 11:58 AM.

  17. #17
    Flashaholic* AnAppleSnail's Avatar
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    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    sorry for the late reply, this is a lot of information to take in and im slowly digesting it. over all it seems there is no "easy" option.
    There is so. The trouble is, it sounds like you're doing your first DIY bike build with the constraints of:

    Budget
    Shipping time
    Experience doing this
    Build space (Refitting an old light instead of working in free space)

    I suggest that first you do the following, then later do the electronics fidgeting in a cramped space.

    0. Find LED and optics for your purpose. Throw, flood, etc.

    1. Buy an LED driver that will run the current you want at the voltage you can give it. This current is determined by how many LEDs you will use, how much current your brightness needs demand, and the voltage by LEDs in series and driver characteristics

    2. Stick the LEDs in a 3/4" copper pipe end-cap, with the LED optic on top. Make sure the inside bottom of the end cap is flat and touches the LED star. You've cleverly drilled holes for the power wires already. Do low-power tests to confirm that heat escapes the LED. Wire these endcap cups to your driver and epoxy them to a handy log to mount on your bike.

    3. Wire the LED to your battery holder, This should be water-resistant at least, with decent wires and an on/off switch. Some LED drivers will change modes with a fast off/on cycle.

    4. Charge up, test a final time, and go biking.
    My biggest light-hog is my camera.

  18. #18

    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by AnAppleSnail View Post
    1. Buy an LED driver that will run the current you want at the voltage you can give it. This current is determined by how many LEDs you will use, how much current your brightness needs demand, and the voltage by LEDs in series and driver characteristics
    so my math should be correct in the edit above in my old post. i could run 3x led in series off 1050ma driver.

  19. #19

    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    so my math should be correct in the edit above in my old post. i could run 3x led in series off 1050ma driver.
    the set up you posted above is made for leds with higher vf like p7, rebels wont handle that set up without 1 extra resistor.
    for simplicity\reliabuility just parallel 3 leds, and 3 cells, and run them off 1 1050ma driver.
    Last edited by alpg88; 03-05-2012 at 02:17 PM.

  20. #20
    Flashaholic* AnAppleSnail's Avatar
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    Default Re: 3x rebel leds: driver question

    Quote Originally Posted by evil-98 View Post
    so my math should be correct in the edit above in my old post. i could run 3x led in series off 1050ma driver.
    3x rebels in SERIES at 350 mA will be about 10.5v in series, give or take, and your cells won't provide that for long. 3x rebels in series at 1050 mA will be more like 12v for the instant before they burn up. I don't think they take overdriving as well as modern Crees.
    My biggest light-hog is my camera.

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