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Pixel colors are off down the length of the string.

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by bob_moody, Mar 12, 2013.

  1. bob_moody

    bob_moody Apprentice Elf

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    I'm working on finishing up 8 pixel based HolidayCoro CoroCanes.
    Each candy cane has 16 WS2811 pixels in them.
    Each cane has a 4 pin waterproof connector soldered directly to the lead in leads on the first pixel.
    Each of the remaining 15 pixels are wired from the factory.
    On the 16th pixel, I pair up CAT5 cable to return the power and signal back to the bottom of the cane (orange pair, green pair, blue pair).
    These pairs are then wired to a opposite 4 pin waterproof connector.

    I currently have 6 of the 8 canes completly wired up and they are under testing.

    What I have noticed, in particularly, when I bring up a pixel in white, cane 1 thru 4 are very white (pixels 1 thru 64 - Channels 1 thru 192), However cane 5 and 6 have a pinkish hue to them in almost like they are a little dimmer.

    I'm driving the pixels with a J1Sys P2 and injecting power with an external 12V 12.5 watt power supply.

    I set up my meter to measure the total current draw. When all 6 canes (96 Pixels) are on as white, there is a total draw of only 1.75amps.

    Any explination for the off color in cane 5 and 6?

    It seems I have plenty of power supply. I'm not in front of the system so I dont have the J1Sys setup readily available. Could a misconfiguration in the controller cause something like this (speed?.. etc)

    I appreciate any input...

    Bob
     
  2. harrison0550

    harrison0550 Full Time Elf

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    Sounds like canes 5 and 6 need power injected directly from the power supply. Think of it as clean full power rather than power running through other things to get there. I had this same issue with my arches. In the pic below the arch all the way to the left had a pink hue to it. I ran power directly from the power supply over to it and cleaned it right up..........

    [​IMG]
     
  3. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Andy,

    I think you nailed it ...
    After I posted I thought, ok, I measured the current draw but didnt observe the voltage drop...

    So I put a meter at the end of the 6th cane (currently the end of the chain)...

    Here are the results.

    With the lights on, alternating red/white stripes, green/white and blue/white stripes, then a chasing red up the 16 pixels, then green, then blue, then white

    I was measuring the voltage a 7.4 to 8 volts.
    With the sequence still playing but all lights off, I was seeing 11.4 v..

    Quite a drop, which would explain the color issues...
    I suppose the voltage drop over the CAT5 returns isnt helping matters since it has to go from the end of the hook in the cane back to the base.

    Do you think if I injected power at Cane 5 from the original supply over better wire that the issues would resolve?

    This has been a very disappointing test run... better to find in March than November.

    Thanks for the tips ...

    You can see the canes, how they are wired and a short video of the test pattern here:

    http://moodychristmas.weebly.com/holidaycoro-candy-canes---part-1.html



    Bob
     
  4. harrison0550

    harrison0550 Full Time Elf

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    "Do you think if I injected power at Cane 5 from the original supply over better wire that the issues would resolve?"

    Absolutely! That will clear you right up.
     
  5. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    How many cores are you usng for power in the CAT5 as cat 5 is really only rated for 1 amp per core so i would suspect the CAT 5 cable isnt helping because if you all the cores then you have 4 amps of capacity for the cable. But power injection should fix your issue as mentioned bt andy
     
  6. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Eddy,

    In the CAT5 return cables, I'm using a pair twisted together each for +12, ground and data.

    Bob
     
  7. Beefer

    Beefer Apprentice Elf

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    We've found that's not particularly reliable (although very convenient) running through the CAT5 cable - you're definitely better off providing separate power cabling, either thicker speaker wire, or extension cables and pigtails from a particular chinese pixel supplier...
     
  8. lithgowlights

    lithgowlights Senior Elf

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    Cat5 as power is pretty poor. It has high resistance, a 500mA rating (1A for some specs apparently), so I'd personally use some speaker wire, alarm cable or similar for power injection - something with a decent current rating - 4+ amps per core.
     
  9. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Thanks to everyone for the comments.

    As recommened, I created a "Y" harness and I'm injecting a fresh 12V supply beginning at candy cane #5.

    I kept the Data and Ground from the output of CC#4 into one connector
    brought in +12 and Gnd from the PS from a second connector
    Then merged the four wires back into a waterproof connector to continue on to CC# 5 thru 8.

    Tested it, and it works like a charm. All the canes appear to have the same colors and intensity.

    I can't thank you all enough. I greatly appreciate everyone here ACL.

    I will post the issues, the fix and the results in my HowTo for future generations... Okay .. for the 5 or 6 people that accidently hit my web site... :p

    Bob



    Bob
     
  10. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Cant win for trying ... I spoke to soon....

    I now have all 8 canes wired and testing..
    I have a power injection for canes 1 thru 4
    I then drop the power after cane 4 and inject a new supply at cane 5 for #5 thru #8

    The thought was if a clean supply would run 1 thru 4 then a newly injected supply would run 5 thru 8.
    Turns out not to be the case...
    5 and 6 look creat and the first 10 of cane 7 look okay.
    From there on (pixel 11 thru 16 of cane 7 and all of cane 8) I'm back to off colors... :'(

    Turns out that 4 candy canes are drawing 1.75 amps. At best the twisted CAT5 is only rated at 1.15amps. Why the first 4 are working fine is beyond me but underrated at more than 1/2 an amp is just asking for trouble.

    I have two options that I can see.

    1. Replace the CAT5 returns with 4 conductor 18ga wire and inject at 1 and 5 as I'm doing now
    2. Leave it as is but create 3 more "Y" adaptors and inject at every other cane (1,3,5,7)

    and the hits just keep on coming ...

    Bob
     
  11. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    The answer is simple, there is voltage drop also occuring between each pixe, so you may start with a lower voltage going in but this may still be a value that allows the LED to function correctly. with the 2811 it is driven by a constant current driver so the 18.5mA output that the 2811 has will be maintained to the LEDs until the voltage drops to a point where the constant current driver is unable to maintain the correct current. With 12vdc you can see about 3 volts drop before you see issues and with 5vdc you can get away with up to around 2vdc before issues appear.
    The reason they start to turn a pinkish colour is because the rated voltage of a single RED led is around 2.2v where as the green and blue is around the 3v in a single LED circuit. So as long as the voltage is appropriatly maintained to the LED ciricuit then the constant current driver will maintain the correct current. And for 12vdc the LED circuit is connected in series so the voltage adds between the 3 leds

    So this is why you would be seeing the first few working and the rest getting more pinkish and proves that the current you require is too high for the cable being used, so you either need more injection or thicker supply with less injection
     
  12. OP
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    bob_moody

    bob_moody Apprentice Elf

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    To validate, here are my testing results

    Cane # Idle Current Draw All White–Current Draw 1 32ma 821ma 1,2 64ma 1377ma 1,2,3 94ma 1565ma 1,2,3,4 123ma 1635ma

    Cane 5-8 have the same power draw w/power injected at #5

    Total draw on PS with 2 power outputs
    Cane 1-4 one feed, cane 5-8 second feed
    Total draw on PS = 2.08 Amps

    Voltage drop testing yielded:
    Cane # Voltage Off/On Drop Off/On 1 12.1 / 11.5 0 / -.6 1,2 12.1 / 10.1 0 / -2.0 1,2,3 11.9 / 9.0 -.2 / -2.9 1,2,3,4 11.8 / 8.3 -.1 / -3.5







    Total drop from unloaded PS is -3.8V

    The source voltage stayed a constant 12.1V measured at the power supply.

    Looking at the tables, technically I should be driving each cane seperatly considering the draw at 2 canes exceeds the current capacity of a pair of 24ga CAT5 cables.

    Thank you Eddy for the post. You explination and the information posted here shows what is happening. It is highly impractical to inject at every prop. I suppose my only other choice is to replace the CAT5 return with the 18ga 4-conductor wire. However, with the wire being used from pixel to pixel, I really dont see that replacing the return cable is going to have that big of an impact.

    I suppose I could open up the joint at pixel 16 and measure the draw and voltage drop there. The difference between that reading and the readings in the table would be the current draw and voltage drop of the 4' CAT5 return wire.

    Bob

    Sorry, the inserted tables didnt survive the post. Looked good while writing it ... but ...
     
  13. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    A suggestion may be to use the 18 guage to supply and then also use the same 18 guage to then bypass the pixels to the end of the candy cane. So basically you will be powering each candy cane from both ends because your just adding another cable that is in parrallel to the candy cane pixels. This will enable you to use less injection with the current design
     
  14. Skunberg

    Skunberg Full Time Elf

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    I note that you mentioned using a cat5 pair for signal (data). There has been several cases of troubles when using more than wire for data. Although pink is normally a sign of voltage drop. I would cut the extra wire to prevent issues.
     
  15. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Eddy,
    Not sure I follow.
    I am feeding the cane with the 18ga.
    Why do I need to bring power back or to the end of the cane at all?
    Couldn't I just tap the power lines sending power to the pixels and just continue on?
    Basically "Y" the power in and out.

    Bob
     

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