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Thread: Desperatly looking for driver (updated kennan driver?)

  1. #151

    Default Re: Desperatly looking for driver (updated kennan driver?)

    Can anybody help me to enable this driver for low voltage cut off?

    I want to set it to cut off @ 9.5v (using 3 cell lipo's)

    I know that on the previous versions one could enable this function... but can it be done on this latest version? I can't find any info in the datasheet.

    Thank you very much
    Jo

  2. #152
    Flashaholic* uk_caver's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    On the previous versions that had a cutoff, it was done by using an extra chip to detect the voltage dropping, which drove the chip-enable input on the main driver chip.

  3. #153
    Flashaholic gillestugan's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Quote Originally Posted by uk_caver View Post
    On the previous versions that had a cutoff, it was done by using an extra chip to detect the voltage dropping, which drove the chip-enable input on the main driver chip.
    Yes, you have to add you own external voltage sensing chip to the driver. It can be done as the AX2002 also have an enable pin.

    It may also be possible to use only a zener diode and a resistor connected to the enable pin, but this is probably not very accurate. According to the data sheet you need somewhere between 0,3 and 2,5V to enable the chip, The actual enable voltage should be able to measure, so you can add a zener with a value just below battery cutoff voltage minus enable voltage. It probably not very stable anyway. Im just speculating and have not tested it. Only tested the enable pin.
    Last edited by gillestugan; 03-27-2009 at 10:05 AM. Reason: deleted bad scheme

  4. #154
    Flashaholic* uk_caver's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Even if the voltage could be selected accurately enough, there might be some odd behaviour with a cutoff circuit that slowly drifted to the point where the chip-enable signal was turned off.

    I'd have thought that a cutoff chip would have some hysteresis built-in to try and avoid oscillation, turning off the driver, then having the battery recover and turn the driver back on again.

  5. #155
    Flashaholic gillestugan's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    you're right.
    I just tested one. Not for battery recovery oscillation but how it behaves between 0,3 and 2,5V. Not good...
    It start to flicker when voltage is below 2,5V Then flickers more and more down to 1,1V where it shuts off completely.
    Not really the the kind of voltage monitoring you want.

    Better to use a real voltage monitoring circuit with enable voltage a little higher than cutoff voltage.

  6. #156

    Default Re: Desperatly looking for driver (updated kennan driver?)

    "For 3 regulars i have 800mA : Good!

    For 6 regulars i have 400mA : No good! But why i have 400mA?"

    Measure the voltage across R220, it should be 250mV. If so, maybe something is wrong with those resistors.

    I transplanted an R200 resistor from my defunct PT4105 driver (death by ringing) and the current bumped up a bit, from 1080 to 1200mA. The new AX2002 seems more robust indeed, even if it lacks the low current mode bonus, it actually superseded the PT4105.

    Does anyone know where to get such low value SMD resistors online, with cheap/free shipping?
    Last edited by zzonbi; 05-10-2009 at 12:49 PM.

  7. #157
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Quote Originally Posted by space View Post
    ...snip... I can't see the R1-label you are reffering to, but I guess you are talking about the R220-resistor. The "-" should be conected to witch ever side of the R220-resistor that is not directly connected to "-" for the board. From your picture it seems like that is the "south-end".space
    I found this reply to italianboy's query a bit hard to comprehend until I'd spent a fair time looking at everything I could find and re-reading. Hopefully I can clarify this for others: "-" for the board are all the many bits connected to "ground" (many components, if you take as an example the circuits on the AX2002 spec sheet) and this is found in a ring of circuit copper surrounding most of the new Kennan/002982 board from KD. If you connect the negative side of your LEDs to this you get an unregulated(?) 1.5A into 2 Crees from 12V source, or 2.5A into one Cree (it squeals that it's about to die shortly when you do this - so don't). So pick up the other, inner (ie: not touching the outer rim of circuit), end of the 220ohm resistor that is adjacent to the empty R2 spot on the board. It's okay to join the inner side of the 220ohm resistor and the nearest solder pad for the vacant R2 with a solder blob and your piece of wire; just don't contact the outer rim circuit, or the other solder pad for R2 that is further away from the 220ohm resistor or you'll get the unregulated(?) 1.5A.

    I also found that putting 5ohm resistor between the 220ohm resistor and the LEDs reduced the current to 700mA (very little heat generated :-) when driving two Crees from a 12V NiMH pack, but was still 1A when only one cree used. 10ohm resisor cut it back to 700mA for a single cree.

    Hope this is some use (my first post here).

  8. #158

    Default Re: Desperatly looking for driver (updated kennan driver?)

    Excellent information and very clear instructions. I have a question though... if you add the resistor to reduce the current to 700mah between the R220 and the - on the LED, does that decrease efficiency? Is the resistor just eating up the other 300 mah? (total electronics newbie... but trying to learn!)

    Thanks

  9. #159
    Flashaholic* TorchBoy's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)



    For a start, mAh (note capital A) is capacity and you mean current, which is mA, for milliamps (or A for amps).

    No, changing the set resistor doesn't in itself change efficiency, because the same reference voltage will still be across that resistor, whatever its total size is changed to, and the regulator sorts out what the current should be from that. The efficiency is calculated by power out / power in. Power = current x volts.

    In practice however there might be a change in efficiency due to the regulator working more efficiently at a different current. The spec sheet indicates the AX2002 works less efficiently at currents under 1 A. (The voltage drop across the LED will also decrease which might also drop the efficiency, but the efficacy - lumens per watt - of the LED will increase.)
    No, a torch does not always mean flames.
    Ian.
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  10. #160

    Default Re: Desperatly looking for driver (updated kennan driver?)

    Thanks for the information and the welcome to CPF board. I have been lurkinghere for a long time and have been playing with these driver boards a bit... and just trying to see what way is the best to use them... use a resistor to set output to 5-600 mA (see, I am learning already lol) and run 3 XPES series off 11.1v... or set the current at 1500 mA and run the XPE's parallel off 7.4v. (I have both battery packs... just trying to determine a cheap way to use the packs...)

  11. #161

    Default Re: Desperatly looking for driver (updated kennan driver?)

    I've been looking through this thread, and I'm a little lost with my quest for an answer. I'm just looking to mod this board so it can output about 350-450mA. What size and where do I need to solder the resistor? Thanks!

  12. #162
    Flashaholic* uk_caver's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    For the newer (AX2002) version of the board, for 400mA, you'd want a current-sense resistor of 0R625, replacing the 0R22 resistor (marked 'R220')

    Looking at my electronics supplier, resistors in 0805 size are available in values of 0R56, 0R62 and 0R68, which would give theoretical output currents of 446mA, 403mA, and 367mA respectively.

  13. #163
    Flashaholic* bshanahan14rulz's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    I don't understand how you search for these boards, or why they are called kennan. I have a 17mm driver board that needs replacing soon (it smells like burning electronics) and am thinking that this board, with all of your research, seems to be the most fun. So, from what I understand, it is a generic board from KD or DX that provides CC (as opposed to a controller board or a buck/dd board)

  14. #164
    Flashaholic* TorchBoy's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Kennan was a constant current driver board from KD (back in the days when their site worked) that scored three out of three: It was inexpensive, efficient, and versatile - it accepted 5-18 V in, and output a constant current for 1 to 3 LEDs. It claimed a lot, did what it claimed, and developed a fan following because of it. It got the name Kennan because KD and DX used to make up pseudo-random names for all their products back then.
    No, a torch does not always mean flames.
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  15. #165
    Flashaholic* bshanahan14rulz's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    hah, they just made up names? So this was an old board that has since been replaced by less efficient but higher current boards? Like, is it not available anywhere anymore? seems like a backwards step for batteries, though I wouldn't care so much if it were for a wired application...

  16. #166

    Default Re: Desperatly looking for driver (updated kennan driver?)

    I don't know about the efficiency of the original Kennan, but this new KD board based on the AX2002 seems quite efficient.

    I am using a modified version to drive a 2S2P MC-E at ~700mA per core. The board uses a sense resistor setup to deliver 1445mA (nominal, based on the output current equation in the AX2002 datasheet) out.

    I didn't measure actual Vf or Iout, but on my bench power supply, the driver requires about 10W of power in when running in regulation. If we assume Vf~6.5V and Iout~1.4A, then Pout~9.1W, or about 90% efficiency.

    The driver runs in full regulation starting at about 7.0V, which seems quite good in terms of voltage overhead.

    One caution. It appears that the inductor may be undersized for this higher current output application. Above 12V for Vin, the driver becomes unstable and Pin starts to behave oddly (it isn't 10W anymore -- it fluctuates from about 4W to 8W). To run above 12V Vin, the inductor should be 33 uH or so. If the board I have uses the same 22 uH inductor that is shown on the KD web site, then that could explain the instability. Unfortunately, the inductor on my board is scrubbed of all markings.
    Last edited by Justin Case; 07-29-2009 at 02:55 PM.

  17. #167
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Just received two of the AX2002's in the mail today. Having not had a chance to play with them yet I can only comment on the shipping and appearance.

    It took exactly 2 weeks from time of order with 8 of those being business days. Packaging was also more than adequate. The inductor also appears to have had no markings or the markings have been removed the same as the post above.

    I will be sure to post some pic's when i get the dimmer mod up and running.

    -Capo

  18. #168
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Well I finally got the time to have a play with my new AX2002's. Did the dimmer switch mod to a pair of the drivers and connected them to 4 ER-E's, 2 a pc.

    Works like a charm, the only problem I have encounter is a slight fluctuation in the current in the first 30 seconds or so of switch on. My guess is the battery voltage is dropping to quickly in that first 30 seconds or so for the drivers to be able to keep up.

    Now some photos for good measure.

    I used a 10kOhm dual rotary pot to control the current to both drivers at once. I only wanted a 1A max current so I have put a 1kOhm resistor (not shown) in series with the pot. With out the 1K resistor it it would dial all the way up to about 1.45A where everything got very hot very fast even with large heat sinks on the LED's.


    A close up of the mod'ed AX2002. Green wires are for the pot, red is + led black is negative. The red and black wires both came with the driver. Note:Its hard to tell in the photo but none of the soldered connections are contacting the outer ring.


    Simultaneous readings of the current output from both drivers. Close enough that i cant tell the difference by looking at them.


    Many thanks to all the previous posters, all the info came in very handy.

    -Capo
    Last edited by Capo_au; 08-20-2009 at 07:16 AM. Reason: More info added.

  19. #169
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    In the post above I dimmed the two drivers at once using a "dual rotary" pot. This means that each drive is essential dimmed by a different pot, so to speak.

    Does anyone know if it would be damaging if i was to use a single rotary pot to dim both drivers at once? They would be powered off the same power source but driving separate led's.

    Thanks.

  20. #170
    Flashaholic gillestugan's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Hi, it wont be damaging, but unfortunately it doesn't work. You will never get the same level on both drivers. When one of the drivers goes high, it will cause the other one to go low, so they will never be in balance. (as long as the pot is connected to output. Maximum level is still restricted by the sense resistor, so it wont damage the driver or led.
    It may be possible to make it work if you use a diodes to block current going both ways between the circuits, but I haven't tried this.

    You may be able to calibrate the output by changing the value of the fixed resistor of one of the circuits, but this is probably not worth it. As you say, it is not possible to perceive the difference in brightness.
    Last edited by gillestugan; 09-07-2009 at 12:28 PM.

  21. #171
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Maximum level is still restricted by the sense resistor, so it wont damage the driver or led.
    Good to hear, that was my major concern.

    It may be possible to make it work if you use a diodes to block current going both ways between the circuits, but I haven't tried this.
    I will give this a try one day when i get the time and post my results.

    Thanks for the help

  22. #172

    Default has anyone used the enable pin on the AX2002

    Hopefully not deviating too far from the original thread but has anyone used the enable pin on the Kennan board?

    According to the AX2002 datasheet it should turn on with anything over 2V. I am finding that 3.3V (output of a PIC) only turns it partially on. I get only about 100 to 150mV on the sense pin and a dim light. Reconnecting the on board 100K pullup and it works fine with 250mV on the sense pin.

    Has anyone else done anything similar, I've testing it on two boards so I am pretty sure I am right but it would be good to get confirmation I am not doing something silly!

    Toby

  23. #173
    Flashaholic* uk_caver's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    I've driven the AX2002 Kennans from PICs, leaving the pullup resistor in place, and pulling the enable pin to ground via a MOSFET when I want to disable the chip.

    However, I have been using them as cheap buck drivers in smart battery chargers, so I haven't needed rapid on/off performance (as would be needed for PWM control for a lighting application).

    When you're trying to drive with a PIC, how are you making a connection - through some resistor, or a direct connection?
    The voltage readings you were getting do seem a little odd at first sight.

  24. #174

    Default Re: Desperatly looking for driver (updated kennan driver?)

    I've used it with both direct connection and with a 47k series resistor, both with the 100k onboard pullup removed.

    I've also tested it with the 100k pullup in place and just probed the enable pin with a high output from the PIC (3.3V). When the pic line is disconnected then the driver is on full, when connected it goes to half brightness. So it seems pretty conclusive that it needs greater than 3.3V to turn it on.

    Using a fet to pull the enable low to turn it off does look the simplest option. The downside is an extra 100uA current draw when off but that will not be a major problem as long as I don't leave it connected for months.

    A shame if this is the case but it is not the end of the world.

    Toby

  25. #175

    Default Re: Desperatly looking for driver (updated kennan driver?)

    a quick update in case if affects anyone else.
    I have put the on board pullup back on the enable and used a transistor from the pic to pull that low (as suggested by uk caver).
    So far at least it is behaving itself properly.

    It is an extra component and 100uA on the off current but I can live with that.

    Toby

  26. #176
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Thanks for the info tobyjmack.

    Any chance you could post a simple schematic, or even just a few photos?

    I'm considering doing something similar but experience in electronic components is limited. So any extra info would be great.

    Thanks!

  27. #177

    Default Re: Desperatly looking for driver (updated kennan driver?)

    Pics and schematic are posted here.... http://forums.mtbr.com/showthread.php?t=554555

    Note that the picture of the board does not have the transistor in the enable line.

    It was more hacked together rather than properly designed so it could be improved (eg filtering the battery monitor, reducing standby current) but it works ok.

    Toby

  28. #178
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Thanks for the link, thats just the info i have been looking for.

    -Capo

  29. #179
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Desperatly looking for driver (updated kennan driver?)

    Does somebody still have old Kennan2 lying around?

    I have an application using analogue dimmed driver boards in the range 30mA to 700mA for a single LED load and supply voltage starting at about 3.5V.

    Kennan2 was optimized for that! But it is sold out at Kaidomain and replaced by Kennan3, which is much more powerfull for currents above 1000mA and increased input voltage range. But it is less efficient with dimmed output, especially when dimmed down below 300mA.

    I'm interested in getting this old stuff. To prevent from misunderstanding, I would like to get those blue Kennans on which all components are arranged orthogonally:



    In case you have such drivers and like to switch them to actual Kennan3 with AX2002, please send me a message on how many of them you can give to me. It doesnt matter if the board has other or more components in place, it is sufficient that it has the same layout only.

    I propose that I order the same amount of Kennan3 at KD in my account but under your shipping address. When you got them, you send your Kennan2 to me. Also direct payment would be possible if you want to get rid of the old stuff without replacing it. There is also possibility that I may 'pay' with rotary switches 1 by 1. I have left about 25 rotary switches with 5 positions (30°) and 4 poles, open before close, upt to 1,5A, axis 6mm, max diameter 18mm including contacts, ITT SB16. This switches are still on the market, now from ELMA



    Reason is, that my actual project (testdevice_3) no more requires high current switching and 2 poles but only low current switching of 1 pole. For this I use a smaller switch from Marquardt (axis 3mm, diameter 12mm)
    Last edited by Tobias Bossert; 10-10-2009 at 02:07 AM. Reason: additional option for payment

  30. #180

    Default rf shielding tips?

    i've got a couple of gen2 kennans running 3 leds in series each at different ma outputs. both are powered by older style wallwarts, not the switching type. running either of them cuts out a few over-the-air dtv stations. i've enclosed one circuit in an altoid box and it's not much help. the wires coming out of the altoid box are very short and the leds are maybe an inch apart on a heatsink. i am not using the altoid box as a 'ground'.

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