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  1. #1
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    KaiDomain (KD) 7135 Drivers - What modes do you use?

    I'm gathering the parts to upgrade a couple of older off-the-shelf bike lights. For the drivers, I've purchased some of the KD 7135 V2 LED drivers.

    The instruction sheet provides details on how to configure the different modes by soldering different bridges. Since this is my first light upgrade, I'm a bit overwhelmed by the choices.

    Lo 3-5Ma, Med 35%, High 100%, AUX0 10Hz strobe, AUX1 2Hz blink, AUX2 SOS, AUX3 beacon.

    The model I have shows the following modes are possible:
    Lo, Med, Hi, Lo, Med, Hi, AUX0, AUX1, AUX2, AUX3
    Hi, Med, Lo, Hi, Med, Lo, AUX0, AUX1, AUX2, AUX3
    High, Med
    High, AUX0
    Med, High, AUX1
    High, Med, AUX1
    Lo, Med, High
    High, Med, Lo

    And, I can solder a different bridge to enable the last mode memory. Whew...

    From what I've read on this forum, the Low is more of a 'firefly' mode. Personally, I'm not interested in strobes.

    I'm considering one of the low, medium, high combinations.

    Which modes have you used? Any particular sequence recommend? Does it really make a difference?

    And, do you like having the last mode memory?
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  2. #2
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    Personally, If a driver only allows hi/low - I use it that way. In my TaskLED drivers I run in Threemode - with a 50ma"moonlight" mode, then a mid power that is half of my max drive current (usually ~500-750ma) then High. Threemode allows you to only toggle between High and Medium with a short click, and have to long press to get back into moonlight mode.

    Given your options - I'd go with either Lo/Med/Hi or the reverse of that - can't really see a difference for having the programming there.

    I guess last mode memory is cool if you accidentally hit your off switch, and turned it back on while still rolling, you'd still have the same level light as before. If stopped - I can't see it being a big deal either.

    I've never used strobe while riding - especially if it is a forward facing light. Blinkies are cool for taillights, I guess.

  3. #3
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    The Low is virtually useless on this driver. Maybe for tying your shoes... Sorry.
    I used the Hi/Aux0 with a red Cree to make a kick-ass rear daylight road light.

    I like 3 useful modes for biking/ running, so I used a different 2800 ma AMC driver for a front light.

  4. #4
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    Thank you both for the responses. Sounds like I might just go with a High/Medium setup sans memory mode. Once my charger comes in the mail I can rig it up and test in the garage.
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  5. #5
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    that's what I'd do - it'll come on in High then a short half press and you're in Med, which is a pretty useful amount of light. I did memory mode on a light for a friend and the double taps to change mode would have annoyed me no end.

  6. #6
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    I use Hi-Med-low on a different AMC735 105C board from DX

    17mm 2800mA 5-Mode Memory Regulated LED Driver Circuit Board for Flashlight (DC 3~4.5V) - Free Shipping - DealExtreme

    Not sure what the current is on your board for those modes.

    I actually use the low for standing around waiting for riders, digging through my backpack, etc

    If the current is too low on the low mode, it's not worth it.

  7. #7
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    Thank you for the responses. I also plan to upgrade a cateye dual and might include the low setting on that build. It would be nice to be able to turn it down and not blind everyone I'm talking to. I could always just angle the handlebars away. So, in that case, I'm still thinking the high/medium setting.

    I knew the charger from DX would take awhile. But, now that I have all of the other parts I'm chomping at the bit to get the build underway. I'm nit picky enough that I want to hook it up for testing before I go modifying the housings.
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  8. #8
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    Quote Originally Posted by El34 View Post
    I use Hi-Med-low on a different AMC735 105C board from DX

    17mm 2800mA 5-Mode Memory Regulated LED Driver Circuit Board for Flashlight (DC 3~4.5V) - Free Shipping - DealExtreme

    Not sure what the current is on your board for those modes.

    I actually use the low for standing around waiting for riders, digging through my backpack, etc

    If the current is too low on the low mode, it's not worth it.
    The low setting on this board is a far more useful than the KD's low.
    The 2800ma setting is virtually as bright with an XML, but a fair bit more efficient too.

  9. #9
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    On the 105C boards at DX the low is 140ma

    It's not really bright but I do use it when off the bike

    Here's the current figures I measured for the DX board

    Low = 140 ma, Medium = 800 ma, High = up to 2.8 amps

    I use medium for all the long climbs and high for faster stuff

  10. #10
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    I wired it up to test last night (using 3AA batteries because my 18650 charger isn't here yet). I now think I'll set it up for High/Medium/Low without mode memory. I'm using a clicky switch so the initial turn on is high. A quick double click and I'm at medium. A second quick double click would drop into low. If I want to go back to high (from medium) I use a slower double click and the driver kicks back to high.

    After tinkering with it for awhile the click pattern came naturally.
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  11. #11
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    Do you actually have to click the switch?

    All I do is tap mine.
    Just enough to disengage the contact points.

    I only click my switch when I am turning the light off or on

  12. #12
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    Quote Originally Posted by El34 View Post
    Do you actually have to click the switch?

    All I do is tap mine.
    Just enough to disengage the contact points.

    I only click my switch when I am turning the light off or on
    The switch I have is from a local electronics supply shop and it does require a full press. This will be my first build so I'm not too worried about getting it exactly right. Knowing myself I can tell you there will be a v2. Probably a v3 of the light, also.
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  13. #13
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    Is it possible to power these boards with four AA cells?

  14. #14
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    Quote Originally Posted by OverTheHill View Post
    Is it possible to power these boards with four AA cells?
    The KD driver I have says it supports 2.5V~4.5V. The NiMH batteries are usually 1.2V, correct? Four in series would be outside of the specs.
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  15. #15
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    i use M & H low is useless

  16. #16
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    Quote Originally Posted by marpilli View Post
    The KD driver I have says it supports 2.5V~4.5V. The NiMH batteries are usually 1.2V, correct? Four in series would be outside of the specs.
    As I understand it the nominal voltage of a AA is 1.2V but fresh off the charger is nearer 1.5V so the combined voltage for 4S will be around 6V. The spec. sheet for the AMC7135 says a Vin limit of 2.7V-6.0V.

    I would like the extra runtime the fourth AA would give and don't particularly want to go to a 3S2P setup to achieve it if the driver is capable of handling 6.0V. I was hoping someone had already tried it but I guess I'm just going to have to test a board to see if it works.

  17. #17
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    i use M & H low is useless
    You forgot at add this to the statement above
    In my oppinion........

  18. #18
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    I just tried 4 x AA with a 700 mA AMC7135 board controlling one XP-G R5. The battery pack was reading 5.63V straight of the charger and the driver did not go boom!

    It probably will though when I build the light

  19. #19
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    According to the spec sheet on the AMC7135, the supply range is 2.7 to 6 volts

    The 7135's should be ok, but, there's also a small chip on the board and I don't have the spec's for that in front of me.

    Chances are that the controller chip is the weak link

  20. #20
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    Atmel runs on 3.3V. So this might be the reason for 2.7-4.5V range on boards wit uC on board.

    Edit: Actually ATiny13 runs from 1.8-5.5V (6V max.)
    Last edited by Toaster79; 11-14-2012 at 04:16 AM.

  21. #21
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    Quote Originally Posted by OverTheHill View Post
    I would like the extra runtime the fourth AA would give and don't particularly want to go to a 3S2P setup to achieve it if the driver is capable of handling 6.0V. I was hoping someone had already tried it but I guess I'm just going to have to test a board to see if it works.
    I'm afraid the fourth AA won't give you any more runtime at all - it'll just give you more heat in the driver. The 7135s are linear driver ICs, dropping excess voltage as heat. If 3 AAs is sufficient to drive your LED(s) then a fourth will just require more voltage to be dropped over the 7135 chips.

    Michael

  22. #22
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    Quote Originally Posted by mfj197 View Post
    I'm afraid the fourth AA won't give you any more runtime at all - it'll just give you more heat in the driver. The 7135s are linear driver ICs, dropping excess voltage as heat. If 3 AAs is sufficient to drive your LED(s) then a fourth will just require more voltage to be dropped over the 7135 chips.

    Michael
    Let me see if I understand what you are saying. If I am driving a single XP-G at 1.4A the Vf will be around 3.5V according to the spec. sheet. Any voltage I supply above this will just result in more heat in the driver.

    So 3 x AAs will be around 4.5V off the charger dropping to a nominal 3.6V
    4 x AAs at 6V off the charger will drop to a nominal 4.8V
    1 x 18650 at 4.2V off the charger dropping to a nominal 3.7V

    Say we assumed a similar cell capacity of around 2700 mAh for each of these scenarios, are you saying that the run times would all be roughly similar but all excess voltage will be dropped in the 7135 chips?

    Apologies for the thread hijack by the way.

  23. #23
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    Quote Originally Posted by OverTheHill View Post
    Let me see if I understand what you are saying. If I am driving a single XP-G at 1.4A the Vf will be around 3.5V according to the spec. sheet. Any voltage I supply above this will just result in more heat in the driver.

    So 3 x AAs will be around 4.5V off the charger dropping to a nominal 3.6V
    4 x AAs at 6V off the charger will drop to a nominal 4.8V
    1 x 18650 at 4.2V off the charger dropping to a nominal 3.7V

    Say we assumed a similar cell capacity of around 2700 mAh for each of these scenarios, are you saying that the run times would all be roughly similar but all excess voltage will be dropped in the 7135 chips?

    Apologies for the thread hijack by the way.
    That's exactly right. The way linear regulators (like the 7135) work is by dumping excess voltage across the IC to regulate the current, like a very fancy resistor. There's no voltage/current conversion going on. So in your scenario 1.4A will be being drawn from each cell, no matter whether there are 3 or 4 (or indeed 1 x 18650). The extra voltage from the fourth AA will entirely be burnt off as heat across the 7135s to regulate the output voltage to maintain the set current. That's why with linear regulators you try and keep the input voltage as close to the required output voltage as possible.

    So having 4 AA cells will simply generate more heat in the driver, but give no more runtime. In your scenario, 3 AAs fresh off the charger will necessitate a 1V drop across the driver, which at 1.4A means the driver is dissipating 1.4W. 4 AAs fresh off the charger will require a 2.5V drop, generating 3.5W in the driver.

    Michael

    Sent from my GT-I9100 using Tapatalk 2

  24. #24
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    Quote Originally Posted by OverTheHill View Post
    Apologies for the thread hijack by the way.
    No apology necessary. I find this kind of stuff fascinating. I'm always learning new things around here.
    Last edited by marpilli; 11-15-2012 at 07:19 AM.
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  25. #25
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    Quote Originally Posted by OverTheHill View Post
    Let me see if I understand what you are saying. If I am driving a single XP-G at 1.4A the Vf will be around 3.5V according to the spec. sheet. Any voltage I supply above this will just result in more heat in the driver.

    So 3 x AAs will be around 4.5V off the charger dropping to a nominal 3.6V
    4 x AAs at 6V off the charger will drop to a nominal 4.8V
    1 x 18650 at 4.2V off the charger dropping to a nominal 3.7V

    Say we assumed a similar cell capacity of around 2700 mAh for each of these scenarios, are you saying that the run times would all be roughly similar but all excess voltage will be dropped in the 7135 chips?

    Apologies for the thread hijack by the way.

    Pretty much how things work with linear regulators. All the voltage above the LEDs Vf will be burnt as heat. Runtimes depend on batteries discharge curve. So in case you're using 3 AA eneloops you can expect longer runtimes because of the linearity of eneloops discharge curve (these can take up to 10A discharge). Quality 18650 like Sanyo, Panasonic or Samsung will be pretty much close but even between these you'll notice difference. 2600mAh Sanyos (pink ones) will probably last longer or the same as Panasonic 3100mAh. Take a 3000+mAh ******Fire 18650 and your runtime will be half of the other batteries or even worse due to high internal resistance of the battery.

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