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Sticker with "110V" on it...

  • eatatjoes10 Wednesday, March 5, 2014 3:59 AM Reply
    Hi folks,
    I received one of these today, and there is a sticker on it: "110V".
    Here in germany we have 230V, so I checked it: it works!

    The 84 LEDs are connected 42s2p (42 in series, two lines parallel), and the voltage to the lines is ~130V, should be ok for the 3528 (2,9-3V per LED, 42x3V =126V).
    There is no switching power supply in it, but a board with some diodes, some resistors, a cap and an inductance (I guess), never saw that before. But it works for 230V.

    My power meter shows me 18W power consumption, very strange for 5W of LED power...
    (84x0,02Ax3V=5,04W)

    Btw.: it's a very "warm white" light, just like in the picture, I prefer a colder white.
    experienced toddler
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  • ebpDoug Wednesday, March 5, 2014 4:43 AM Reply
    The circuit will be a "capacitive divider" type. It works by relying on the reactance of a capacitor to drop the voltage to the LEDs. Typically the capacitor is in the range of about 1/2 to 2 microfarads, and is usually a film type. Because it uses reactance instead of resistance the circuit is quite efficient. The drawbacks are that there is no specific regulation of the average current and the current through the LEDs has a high ripple component.

    Unless your meter measures true power, usually done by taking many many samples over a full line cycle, calculating the instantaneous product of voltage and current for each sample, then dividing by the number of samples, you won't get a value that is correct for the average current into the LEDs. This is because input current is only able to flow during the time the instantaneous input voltage is higher than the forward voltage of the LED string. This is usually modified a bit due to use of an electrolytic capacitor in parallel with the LED string, but that doesn't make a huge difference.

    Vojta7 posted a schematic for a capacitive divider circuit in
    http://club.dx.com/forums/forums.dx/threadid.1360453
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  • desolder Top 10 Forum Poster Wednesday, March 5, 2014 12:36 PM Reply
    Those capacitive current limiting drivers aren't supposed to be compatible with wide voltages. Using a 110VAC bulb in a 240VAC socket could result in some excitement!
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • eatatjoes10 Tuesday, March 25, 2014 2:32 AM Reply
    Update:
    The lamp died after two weeks use at 230V (germany).
    I wrote, it seems to have the correct voltage to the LEDs, even with the 110V sticker on it, but after two weeks it is dead, and the plastic housing started melting!!!

    It looks like the 18W, that my power meter was showing, is correct, and 13W of power was converted to heat.

    @all DX customers
    Do not use this lamp with voltages like 220V or more!

    @ebpDoug
    @desolder
    yes, that's the same circuit I found, definitely not for 230V!
    I'll write to DX to change the desciption to "only for 110V", using it at 220V is dangerous
    experienced toddler
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  • desolder Top 10 Forum Poster Tuesday, March 25, 2014 2:42 AM Reply
    YIKES! Thanks for the update eatatjoes10. It really did turn "exciting" in the end. Since the description was wrong and it didn't work at 230V as advertised, DX owes you a refund. You should submit a ticket.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • eatatjoes10 Tuesday, March 25, 2014 3:11 AM Reply
    Hi desolder,
    correct, I'm preparing the RMA, and took some pictures.
    I openend the lamp and found one of the three wires (the common "-") was desoldered. After soldering it back to the board the lamp does work again. But I can also see, that the plastic column, that holds the board next to that solder point, is molten, so it was pretty hot in there...
    I've put that lamp to my desktop-light now, to see what will happen. But I bought six different sku's of these lamps for a friend, and there is one more that died the "hot way".
    This is not very funny.
    experienced toddler
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  • eatatjoes10 Tuesday, March 25, 2014 3:16 AM Reply
    Wow, what an experience:
    it took only five minutes to completely kill it!!
    The LEDs just died within 10 seconds, and the lamp was too hot to touch it! And the plastic housing is completely deformed...

    I repeat it:
    Do not use this lamp with voltages like 220V or more!
    experienced toddler
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  • ebpDoug Wednesday, March 26, 2014 2:52 AM Reply
    It sounds like your power meter really does do the job properly. I've seen some that are quite inexpensive but quite good and others that are very poor for non-linear loads.
    Getting about three times the nominal power sounds about right given the LED string voltage.

    Can you read the values of the capacitors and resistors in the circuit? If you can, I'll do the calculations for what the expected power would be at 230V (actually, I'll use a simulator - calculating these things "by hand" isn't exactly quick and easy).
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  • eatatjoes10 Thursday, March 27, 2014 6:57 AM Reply
    Hi ebpDoug,
    I tried my best with "tinyCAD" (first time), and I hope I didn't mess the traces up...
    Also, these are my first pics on Flickr, I hope the links will work:
    https://www.flickr.com/photos/[email protected]/13516302433/
    https://www.flickr.com/photos/[email protected]/13435448363/

    The two R47k are tiny (1/8W), R10 is huge (1W?), the cap 3400nF is a big brownie...

    03.30.2014, 19:58
    Edited the links to flickr
    experienced toddler
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    post edited by eatatjoes10 on 3/31/2014 at 1:58 AM
  • desolder Top 10 Forum Poster Thursday, March 27, 2014 7:58 AM Reply
    eatatjoes10, can you tell how the LEDs are wired? Are the 84 LED wired in a 14 series by 6 parallel configuration, or perhaps 28 series by 3 parallel? That bit of information will be helpful for ebpDoug to simulate the circuit.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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