Flickering 50W Outdoor RGB LED flood lights

Discussion in 'General Electronics Chat' started by ldavenpo, Dec 25, 2012.

  1. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Merry Christmas!

    I've just purchased four "50W LED RGB Color Change Flood Outdoor Light Lamp Remote Control 85-265V" from a seller through Amazon.
    (http://www.amazon.com/gp/product/B008IYFV40/ref=oh_details_o00_s00_i00)

    When I apply power to them they turn on flickering. If I cycle the power many times, they will eventually turn on correctly, but once I turn the power off and then on again, they most likely flicker. I've discovered that if I get them turned on correctly and then leave them on for a few hours, they are more likely to turn on correctly (though still with no predictability).

    The seller is sending new ones. But I'd still like to know what the problem is and see if I can salvage the ones I have.

    Here's a demonstration video:
    https://dl.dropbox.com/u/37537150/LED/LED Malfunction.mp4

    And here are a few pictures of the electronic components:
    https://dl.dropbox.com/u/37537150/LED/IMG_1175.jpg
    https://dl.dropbox.com/u/37537150/LED/IMG_1177.jpg
    https://dl.dropbox.com/u/37537150/LED/IMG_1178.jpg


    Anyone have any thoughts?

    Thank you!
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,130
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    Wow- those are really low prices!
    Not too surprised that the quality is low.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,057
    3,818
    There is a hole on the PCB labelled, Vcc. It looks like nothing was ever soldered there. A wire is covering another label, it looks like it is also labelled Vcc (lower left corner of the board in the photo. I am not sure if both Vcc are electrically connected.

    The person assembling the board may have left the connection out since they are connected by a circuit trace. However, the narrow circuit traces may be more resistance than the board was designed for. Try connection these two points together with some thick wire and good clean solder joint.

    This is a diagnosis just based on armature detective work and no knowledge of the circuit - but worth a try.

    Also, try to read the labels on the two chips in the upper right corner of the board and let us know.
     
    ldavenpo likes this.
  4. vrainom

    Member

    Sep 8, 2011
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    I'm not 100% sure but I think the problem might be the resistors you added in series with the led. Normally the led's driver is constant current controlled and if you artificially lower the circuit's current consumption the output flickers.
     
  5. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Um... thanks for that input.
     
  6. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
    9
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    Interesting observation! Okay, I will try that tomorrow and let you know what effect it has. Thank you for the suggestion!
     
  7. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Excuse my ignorance - the resistors are the large ceramic rectangular pieces between the circuit board and the LED's? Do you think those are there because these LED's are dimable? I'm not sure what their function is....

    Also, something else I didn't mention previously: If the lights have not been on and I turn them on, they flash about 98% of the time. Once I get the lights on and functioning correctly, if I leave them on for several hours and then cycle the power, the chance that they turn back on correctly (not flickering) seems to increase significantly (as much as 50%). But if I leave them off overnight, they are back to flickering most of the time.... Is that a clue?

    Thank you for your thoughts!
     
  8. panic mode

    Senior Member

    Oct 10, 2011
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    what is the power source for this thing?
    do you have a multimeter?
    did you try to see what happens with the voltage?
    is it steady, fluctuating, rising and falling slow or fast when powered on/off?
    are the Vcc pads internally connected (zero ohm) or the pad with no wire is different net?
     
  9. vrainom

    Member

    Sep 8, 2011
    109
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    Oh, yeah, you said you bought it assembled. Well normally those constant current supplies flicker when they try to output the rated current but can't and then reach their maximum output voltage and reset.

    However I think I can see why the led needs some resistors to balance the power between the color chips as they each work with different voltage drops, I'm not sure about the values though.

    What I would consider doing is bypassing the color controller to see if that's the problem connecting the negative from the constant current supply directly to the three resistors and see if that works.
     
  10. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    New Clue:

    These lights have 8 brightness settings (let's say #1 is the dimmest and #8 is the brightest). If I set the brightness to anything #3 and above, the lights will flicker when powered on as mentioned in my original post. If I set the brightness to #2 or #1, the lights turn on steady every time (but quite dim!). (Setting #3 will almost always flicker and then turn on.)

    "Panic Mode" - I do have a multimeter and checked the output when I first turned one of the lights on - it was just over 42 volts DC. I did not continue to monitor. I assumed that if it was putting out full power then the lights should immediately illuminate at their brightest setting. What is a VCC pad and "different net"?

    "Vrainom" - how would I bypass the color controller? Black wire coming in goes bypasses circuit board and goad directly to resistors? And you would expect full brightness white light?

    Thanks everyone!
     
  11. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Here are two more pictures: a closer up of one of the circuit boards (this one has the second "VCC" filled with solder), and the remote control:

    https://dl.dropbox.com/u/37537150/LED/IMG_1188.jpg
    https://dl.dropbox.com/u/37537150/LED/IMG_1190.jpg

    Upon further review, the lights seem to consistently start correctly at a setting of 6, but flicker at the highest settings of 7 or 8. I thought maybe there was a difference between white or individual colors, but this does not seem to be the case after all.

    "Panic Mode" - the voltage is a constant 41.7 volts. The two VCC pads are internally connected - have zero ohms between them.

    Thanks!
     
    Last edited: Dec 30, 2012
  12. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    I just received four replacement units from the seller. All four function correctly (though one needed the IR wire re-soldered). This batch has a different driver (an open circuit board with no voltage markings) and controller board than the previous batch.

    I decided to test the driver by running wires from the "good" light driver to the control board of the "bad" light. The "bad" light worked perfectly. I believe it is safe to assume that the drivers on the first batch of lights are the culprit?

    The DC voltage from the driver on the new lights is 26.5V. The DC voltage from the driver on the old lights is 41.7V. I did not measure the amperage.

    My prediction would have been just the opposite: that the old lights were not getting enough power to turn on all the LED's (at the highest settings), but were getting enough power to turn them on at the reduced settings.

    At any rate, my plan is to purchase new drivers for the old lights. Is it reasonable to assume that a 50 watt LED driver that produces up to 30VDC and 1500mA should solve this problem?

    Thanks!
     
  13. vrainom

    Member

    Sep 8, 2011
    109
    19
    The red led series require ~26 volts to light up but the blue and green leds require a little bit more voltage, around 33 volts to light up properly.

    However I have the hunch that the power supply is not the problem but either the power resistors going to the led or the rgb controller. Maybe you could check that by hooking the supply from another flood light to the flickering one.
     
  14. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Sorry - I wasn't clear. That is what I did. I hooked the power supply from a good light to the flickering light and then the flickering light worked correctly. I did this via a jumper wire joined in between the power supply and the circuit board of the good light to the same place on the flickering light.

    It seems to me the power supply is the problem. Right? I just don't understand the the voltage differences....
     
  15. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
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    Its VERY common for a constant current driver to flicker when the forward voltages of the LED's are greater than the rated DC output of the driver.. I see it all the time.
    It just cannot regulate its current properly and will either flicker or the current will be too low.

    The resistors are more than likely to "attempt" to even out the current in each string based on the different Vf of each color/channel.
     
  16. ldavenpo

    Thread Starter New Member

    Dec 25, 2012
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    Thanks "Mcgyvr". Can you help me understand this:

    Flickering lights have DC voltage of 41.7v from power supply to circuit board and will only start on dim setting.

    Good lights have DC voltage of 26.5v from power supply to circuit board and function correctly.

    Using the power supply from the good lights (26.5v) makes the flickering lights work correctly. Why would a lower voltage fix the problem?
     
  17. vrainom

    Member

    Sep 8, 2011
    109
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    Oh, sorry, I didn't get that the first time. Then what I think might be going on is that the faulty supply can't sense its current output. This kind of supplies try to output their rated current whatever the voltage drop is within their range, that's why they're marked with such a wide voltage output. However if the supply don't sense it's outputting its rated current it raises its voltage up to its limit (that's why you might see 41v) and then shuts off momentarily, hence the flickering.
     
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