The new sku.3256 drivers- Mtbr.com
Results 1 to 19 of 19
  1. #1
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60

    The new sku.3256 drivers

    After three (3!) months of waiting, I have finally received my 3256 drivers from DealExtreme. Didn't do any detailed tests but I did check the Iout (800mA) with a quite depleted 4 NiMH pack (Vin=4.15V under load). The efficiency was 85%.
    It seems there are a few changes from the older design. This board uses the C310 and also has a bit higher Rsense (lower current?).


  2. #2
    Five is right out
    Reputation:
    Join Date
    Sep 2006
    Posts
    3,174
    Hmm... the pre-attached leads are the LED in/out? Where do the power in/outs go, and does the board use a momentary or contact switch? There appears to be bugger all documentation on the DX site, unless I'm missing something!

  3. #3
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60
    Actually there is quite a lot of user submited documentation on the DX product page (reviews, forum posts). You connect your battery on the other side of the board (the middle is positive, the rim is negative). This is a '1-mode' board for the contact switch that works very nicely with the 4xAA NiMH input. Look through this forum. There are already a few threads dedicated to this board.

  4. #4
    I like Monkeys
    Reputation: VaughnA's Avatar
    Join Date
    Jan 2004
    Posts
    886
    That looks like the new ones I got about a month ago. The good news is that they seem to take a 7.4v pack just fine without smoking. 11 of 12 I received survived and I toasted the 12th with my own stupidity. I do recommend replacing the leads with something a little more substantial. You can't beat these things for the price. And by using one per LED you have redundancy in case of a problem.
    What do I want to be when I grow up.....Dead!

  5. #5
    mtbr member
    Reputation: Lumbee1's Avatar
    Join Date
    Dec 2004
    Posts
    1,908
    How hot do these get? Are they true constant current?

    I built a headlamp using a old CREE P4 I had laying around. I picked up three pack of highly recommended constant current drivers from Dealextreme. I wired everything up and was about to make the final connections when I decided to do a test with the light. Literally seconds after applying power, the light is on but I feel heat, lots of heat. I check everything over and all looks good. I driver is warm but cooling quickly. I turn the light on again and feel heat. I let it go for a full minute. The light works fine but the driver is very hot. It appears as though the heat has stabilized but a very high temperature. Just by the amount of heat from the driver, I would guess I was getting about 60 to 70% efficiency and the rest was converted to heat. There was no way I was about to pack this driver into a head lamp and put it on my head.

    BTW, shortly after my tests, I checked reviews on the driver and saw others posting similar experiences. I guess you get what you pay for.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60
    @VaughnA
    That's great news! I still don't have any 18650 cells but it's nice to know that it's possible to drive them with a 7.4V packs. On the other hand, after waiting for three months I don't know would I be willing to risk burning even one of them (I need all four!).

    @Lumbee1
    What drivers and what input voltage are you talking about? These drivers are getting just slightly warm with a 5V input voltage and I don't think they will need any heat sinking. Maybe you got some of the linear drivers such as a 7135 based ones (the same Iin and Iout). Those drivers heat up nicely when driven with a Vin much higher than the led's Vf. sku.3256 should be more efficient and are probably the best DX drivers for the 4NiMH input.

  7. #7
    mtbr member
    Reputation: Lumbee1's Avatar
    Join Date
    Dec 2004
    Posts
    1,908
    I just did some additional research. I got three from the bad batch of drivers. I need to modify R1 to make them work correctly.

  8. #8
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60
    As my lights use a plastic container for the electronics with just a few small ventilation holes I wonder is there a chance of drivers overheating with a 4NiMH batteries? My testing shows that the drivers get moderately warm to touch but I had to partly wrap them in tape for electrical isolation (it's pretty cramed in the light housing). How tough are these buggers?
    How hot would you say is too hot for the drivers? Quite warm to the touch? Too hot to touch?
    I have tried to make a heat sink for one of the drivers (the one I am planning to use more often) with a thick piece of aluminium that partly sticks out of the plastic container but I am afraid that the thermal contact between the driver and the heat sink is not very good (a bit of 'gummy' thermal pad). It's really hard to make a good contact, with one side having two wires sticking out and the other having a lot of elements of unequal height.
    The drivers are really cheap but I need all four of them and they are really hard to get from the DX. What do you think? Did I even have to bother with the additional heat sinking?

  9. #9
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    251
    With 4 NiMh the drivers should be fine. Another option would be AMC7135 boards, DX has them in huge quantities. But they are better suited for li-ion batteries, the difference in led forward voltage and battery voltage is a lot smaller. With 4 NiMh batteries the efficiency of a AMC7135 board would be only 66%, quite bad. 3 NiMh's would be more efficient, but the battery voltage is probably too close to the led forward voltage.

    The problem of overheating the 3256 boards was always with 2 li-ion cells in series as energy source. I have 4 boards with melted transistors laying around... Most boards seem to be able to handle 8.4V, but some clearly don't.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60
    Thanks! So, I'll probably be fine. I decided on 3256 drivers for the lower price, much higher efficiency with 4xNiMH setup (more or less the same efficiency with a one 18650 cell) and simple 1-mode operation (important when you are driving 4 leds). An odd number of NiMH cells was out of the question as I don't have a 4-channel charger. I also got one AMC7135 16-mode driver to play with.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    71
    Just a warning to make sure you check the drive current before using them.

    I just got another batch (after quite a wait) and just checked their output currents. Running off a charged 2x18650 series pack (so ~8v), they were:
    1 @ 1.05A
    1 @ 1.1A
    1 @ 1.3A
    1 @ 1.4A

    You wouldn't want to be running 1.4A for long if your heatsinking was only setup to cope with 800mA

  12. #12
    Five is right out
    Reputation:
    Join Date
    Sep 2006
    Posts
    3,174
    Hmm... another warning. I just got a batch of these and have tested 3 at 7.4V. I'm getting figures that settle at 1.2, 1.3 1.4A. They actually start .2 higher, then decrease to these figures after around 5 minutes.

    I haven't checked the fourth... I've run out of connectors.

    I don't even want to think about what sort of currents would be running with 2 fully charged Li ions (i.e. 8.4V).

  13. #13
    Five is right out
    Reputation:
    Join Date
    Sep 2006
    Posts
    3,174
    More to my above post. I have now tested all four with a 5V input and I get outputs of:

    1.4A
    1.3A
    1.2A
    1.2A

    I'm not sure if I should go ahead and use any of these. Does anyone have experience running XREs at 1.2A for extended periods, with decent heat sinking, or would this be a bad idea?

  14. #14
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    453
    I use those drivers for running 2 XREs in parallel.

  15. #15
    jim
    jim is offline
    mtbr member
    Reputation: jim's Avatar
    Join Date
    Jan 2004
    Posts
    37
    I just killed an XR-E running off one of these newer 3256 drivers. Ran it for about 10 minutes with more than adequate heat sinking before it failed Verified XR-E death by swapping 3256 board to another XR-E which fired up nicely.

    I need to use a resistor between my switch. Anyone have any idea what ohm resistor I should use to achieve 750 - 800ma from this driver? It should be less than 400ohm but I've no idea how to calculate it? Any clues?

    Thanks in advance.

  16. #16
    Five is right out
    Reputation:
    Join Date
    Sep 2006
    Posts
    3,174
    How much current were you getting through the LED?

    If you go to the discussion board on DX for this driver, there is a post that explains how to shave down a resistor to reduce current. I've managed to get one of my 1.2A drivers down to 950mA by this method. I can't seem to get it down any further though.

    From my batch, I'm convinced that these drivers have really, really flakey quality control. I'm going to run one in a test light and am setting my expectations low.

  17. #17
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    60
    Quote Originally Posted by jim
    I just killed an XR-E running off one of these newer 3256 drivers.
    You forgot to give us the input voltage. I have never heard of anyone burning up one of these drivers with a 4NiMH so I am guessing a 2x18650? My batch is pretty well regulated (800mA) with a 4NiMH battery pack. The Iin starts at about 680mA on a freshly charged pack and rises up to 800mA when the batteries are nearly drained.
    A freshly charged 2x18650 packs should have close to 8.4V so you need to lower that for about 2V-2.5V to be on a safe side. For that you want to use a 3.3ohm resistor with a 2W or better rating.

  18. #18
    jim
    jim is offline
    mtbr member
    Reputation: jim's Avatar
    Join Date
    Jan 2004
    Posts
    37
    Quote Originally Posted by dsvilko
    You forgot to give us the input voltage. I have never heard of anyone burning up one of these drivers with a 4NiMH so I am guessing a 2x18650? My batch is pretty well regulated (800mA) with a 4NiMH battery pack. The Iin starts at about 680mA on a freshly charged pack and rises up to 800mA when the batteries are nearly drained.
    A freshly charged 2x18650 packs should have close to 8.4V so you need to lower that for about 2V-2.5V to be on a safe side. For that you want to use a 3.3ohm resistor with a 2W or better rating.
    Oops, yes, 2 x 18650. Thanks for the information.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    71
    I successfully shaved 2 of mine down to 850mA a while ago, and they still work fine.

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.