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Trying not make the same mistake twice !!!

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by bob_moody, Mar 29, 2013.

  1. bob_moody

    bob_moody Apprentice Elf

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    Hello Everyone,
    I know several members here at ACL helped me with the issues I had when I built my pixel candy canes. As it turns out, injecting power every 3rd cane (At point 1,4 and 7) did the trick. They are working perfectly and my pixel life is good... THANK YOU ALL !!!
    Now, I am ready to start my next project and again it is pixel based. I'm replacing the MERRY CHRISTMAS sign that was on the roof and was destroyed Christmas day by the weather with a new one. This time instead of using LOR and C9 incans, I'm going to use 26mm pixels. For example the first letter in Merry (the M) is set up like this
    X X
    X X X X
    X X X
    X X
    X X
    X X
    X X
    Where each "X" represents a pixel.
    The sign will require about 219 26mm pixels to complete. I am looking at these pixels from Ray Wu
    http://www.aliexpress.com/item/26mm-diameter-TM1804-LED-pixel-module-3pcs-5050-RGB-SMD-LED-DC12V-input-IP68/597351990.html
    Considering my power supplies are each rated 12V@12.5 amps, I calculate I will need 2 power supplies to run the sign. I also figured I can use one to run the MERRY part and one for the CHRISTMAS part.
    What I would like some feedback (read as HELP !!!) on is the injection points and how well the DMX signal will travel. If I understand since there wont be any real distance from pixel to pixel, the signal regeneration should keep the DMX signal alive and well down the string.

    The MERRY part of the sign will use 17,18,18,18,9 pixels respectively for each letter.
    Christmas will use 13,17,18,15,15,11,17,18,15 pixels respectively for each letter.
    With the knowledge gained from the candy cane project. I figured breaking the letters up like this:
    ME - RRY - CHR-IST-MAS which gives me 35,45,48,41 and 50 pixels in each grouping (also known as injection points) with a final injection point into the last S of the sign.

    If this made ANY sense at all, I sure would like some input on project. Am I grouping to many pixels? Considering the pixels I want to use do I need to reconfigure the injection points? Do I have enough injection points?
    Thank you for reading the LONG post and for all the help ACL has given me in the past. I really do appreciate it.

    Bob
     
  2. AAH

    AAH I love blinky lights :) Community Project Designer

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    Some feedback (aka help) is that the signal isn't DMX but rather SPI in a given format TM1804 format in this case. I was going to suggest that you use 2811 based pixels but it looks like there isn't many varieties of those style. The 2801 is a more popular format and is 10c a pixel cheaper so if you're not committed to 1804 you may prefer 2801. If you talked to Ray and he'll do 2811 ones for you then I would expect that they would be another 5 to 10c cheaper again. The distance between any 2 points with 2811 pixels is 15m so it has some major advantages other than just being cheap. Your injection points look good but I personally would go with a single 350W power supply.

    http://www.aliexpress.com/store/701799/search?SearchText=26mm+pixel
     
  3. OP
    OP
    bob_moody

    bob_moody Apprentice Elf

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    Ahh, Al, or Alan.... Thank you for the link. I thought I had researched the 26mm pixels pretty well but I missed the 12V 2801's and since my J1Sys P2 would support the TM1804's I didn't continue the search.
    My bad on the DMX, SPI issue. An unfortunate entry on my part.
    I'm not married to the 1804's. In fact the pixels in my Candy Canes are the rectangular 2811's. As for power supplies, I picked up a batch (5 pack) of the 12V@12.5 amp supplies for $25 and I have currently have 2 committed. One for my RGB Node North Pole toppers and one for the Candy Canes. I can understand having the single PS but since I have these on hand unless there is a specific technical reason such as injecting noise into the SPI data stream with two different supplies I'll most likely use what I have on hand.
    Once again, I really appreciate the input and the link.

    Bob

    UPDATE: I just noticed that one of the links shows the voltage at 12V in one spot then shows a working voltage of 5V in another. Are the 2801 pixels 5 or 12 volt? That may be the reason I went to the 1804. I recall it being the only 26mm I found at 12V. Of course IF there is a real advantage, then I can buy a single 5V 350W supply (?) and use the cheaper 2801(?)
     
  4. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Well I took the advice that I'm sure many where thinking and happily to polite to say.....Bob, read the %&$# manual!
    So I went to my other friend, Mr. Google and read the data sheets on the 2801.

    The 2801 is a 3.3 to 6 volt device which now that I think about it is why I turned to 1804. Since I have 12v supplies on hand, I went that direction.

    I will continue my research and also look into power supplies. I will also have to research the forums on 5 vs 12v. I recall FastEddy et.al. posting an explanation on the pros and cons of each along with current requirements and wiring issues.

    Once again, thank you all for the forum and support.

    Bob
     
  5. fasteddy

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

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    One of the things i personally dont like about the 1804 is that it uses constant voltage regulation as apposed to constant current regulations. LEDs are current devices and thus its current that should be controlled not voltage.

    The 1804 uses voltage levels to maintain the current as voltage and current are directly related in Ohms law, this design works but in my opinion if there is an alternative that is constant current controlled like the 2811 then ill choose the constant current every time.

    Both will still give you blinky

    Heres a couple of links

    http://auschristmaslighting.com/forums/index.php/topic,2595.0.html for the differences between 12vdc and 5vdc

    http://auschristmaslighting.com/forums/index.php/topic,3812.0.html for current draws

    http://auschristmaslighting.com/forums/index.php/topic,3668.0.html for understanding voltage drop
     
  6. OP
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    bob_moody

    bob_moody Apprentice Elf

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    Has anyone run across a 26mm pixel with the 2811 chip?
    Like the topic of this thread, I dont want to make the same mistake twice or inject another degree of difficulty in operating it.

    would the 2801 be a good second choice? I know I would have to update and get a 5V supply, but I found some 350W 5V supplies that should run the element (single PS as suggested by Alan)

    Thanks for the links Eddy. I really appreciate it.

    Bob
     
  7. fasteddy

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

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    The 2801 is a great alternative and would be my second choice to using the 2811. But i would also ask Ray to see if he can get the 26mm in 2811 with 3 x 5050 LEDs and 12vdc

    The 1804 will still do what you want perfectly and is 12vdc.
    http://www.aliexpress.com/store/product/26mm-diameter-TM1804-LED-pixel-module-3pcs-5050-RGB-SMD-LED-DC12V-input-IP68/701799_597351990.html

    The 2801 5vdc model may not be what your looking for as it only has the 1 5050 LED compared to 3 5050 LEDs for the 1804
    http://www.aliexpress.com/store/product/26mm-diameter-WS2801-LED-pixel-module-1pcs-5050-RGB-SMD-LED-DC5V-input-IP68-frosted-cover/701799_592885823.html
     

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