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Thread: Pixel power calculator and associated power injection article

  1. #1
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    Default Pixel power calculator and associated power injection article

    Just sharing, I created the following power injection calculator and associated article. Hope it helps some of you out while designing your display.

    Calculator link: http://spikerlights.com/calcpower.aspx

    Article link: http://spikerlights.com/pwrinjection.aspx

  2. Thanks pixelpuppy, rfallatt thanked for this post
  3. #2
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    Default Re: Pixel power calculator and associated power injection article

    Super cool! Got this baby bookmarked. Thanks for doing it
    Last edited by pixelpuppy; 11-08-2017 at 05:46 PM.

  4. #3
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    Default Re: Pixel power calculator and associated power injection article

    This is awesome - thanks much. Pretty timely for me as well as I have been looking over power injection posts the past few days. Excellent work!

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    Default Re: Pixel power calculator and associated power injection article

    How about adding some text discussing using 24V or 36V distribution, using buck regulators, etc. Being able to size out the correct gauge of wire when using higher voltage and thus lower currents. Nicely put together I might add. The graphical representation helps drive the message (is that why management likes power points so much?)

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    Default Re: Pixel power calculator and associated power injection article

    So, If I want to have a 4 strings of 50 pixels connected end to end for a total of 200 pixels (12v), I could have the 12v power applied to the beginning of the string and the end of the string from the same power supply and be OK, correct? Each 12v power connection will feed 100 pixels without problem regardless of the direction of the power flow?
    Kevin

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    Default Re: Pixel power calculator and associated power injection article

    Quote Originally Posted by kev View Post
    So, If I want to have a 4 strings of 50 pixels connected end to end for a total of 200 pixels (12v), I could have the 12v power applied to the beginning of the string and the end of the string from the same power supply and be OK, correct? Each 12v power connection will feed 100 pixels without problem regardless of the direction of the power flow?
    That is correct on both fronts.

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    Default Re: Pixel power calculator and associated power injection article

    Quote Originally Posted by Utimgr View Post
    How about adding some text discussing using 24V or 36V distribution, using buck regulators, etc. Being able to size out the correct gauge of wire when using higher voltage and thus lower currents. Nicely put together I might add. The graphical representation helps drive the message (is that why management likes power points so much?)
    I've been thinking about adding a section for "Where things get wonky" and can add it there.

  9. #8
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    Default Re: Pixel power calculator and associated power injection article

    Fusing concepts may be interesting and how to use one of the power distribution boards that are out there in a setup as you defined might be helpful to some as well. Again, nice work.

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    Default Re: Pixel power calculator and associated power injection article

    Any chance of a mod to remove power details? The default starts at pixel 0. I can't power at pixel 50 and 150 with the tool. Being able to show "what if's" is nice but the additional option would help.

  12. #10
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    Default Re: Pixel power calculator and associated power injection article

    I know this is an old thread, but I have been digging a bit deeper into some real world measurements versus theory and have run into a discrepancy. I have been using 5V pixels and doing power injection since 2013, so I'm very well versed with both topics, but I recently find myself working on something that is going to "push the limits" on what I have done in the past and hoped this calculator would be helpful with that exercise. I am blaming Bill Porter's awesome YouTube videos for making me question the way I have historically performed some "limit pushing" power injection... which has caused me to rethink some of my elements, in this case, the 4000+ pixels that I wrap into our Florida live oak (and the second 4000+ pixels we are about to add to our neighbor's comparably sized live oak next year to create perfect symmetry in our display). I thought that I liked power injection, but Bill really takes it to another level...

    This "limit pushing" I keep referring to is my interest in running up to 300 pixels from one F16 output to each LONG branch on the oak tree. Up until now, I have split this into two outputs of 150 pixels each, but I have finally maxed out the F16 plus expansion controller. The darn tree keeps growing each year and I would like to set us up for future expansion. Although we run 300 pixels per output for our window matrix panels, we do not run that many pixels in almost any other location of our display (which is around 35,000 pixels) because of the amount of power injection cabling that it would require. With the pixel matrix panels, it is easy since all of the power injection occurs within an 8' width.

    I went out to the garage and created a 300 pixel string, multiple injection points, measured a bunch of voltages, and nothing was agreeing with the RGB Pixel Calculator. I was getting frustrated, mostly because, I could not get a good "white" through all 300 pixels... so I decided to get to basics, using the RGB Pixel Calculator linked in the first post of this thread. If I go there and punch in 50 lights, 5 volts, 0.24 watts, 6 inch spacing, 100 percent intensity, and 18 AWG wire (which is all appropriate for what I'm using), the graph shows a voltage at pixel 50 of around 4.4 V. I do not see that. No wonder the results were not matching up for the 300 pixel string. The string of lights that I have is measuring 3.804 V at pixel 50. That is almost a half volt difference. I verified that the voltage leaving the F16 is 5.03 V, so we're good there.

    I tried some additional tests... for instance, I cut the intensity out of the controller to 50%. Now the voltage is around 4.3 to 4.4 V, now we're talking! But the RGB Pixel Calculator suggests that, with 50% intensity, the voltage at pixel 50 should be closer to 4.6 V... still off by a couple tenths of a volt, but that is better than a half volt. I thought that maybe the string of lights was bad, or the output on the controller, so I measured six different strings of lights (from two separate years / batches by the looks of the strings) on eight different outputs from the F16 and I saw a mean voltage of 4.36, a median voltage of 4.34, and a standard deviation across all measurements of 0.07 V.

    I do understand that doing this type of measurement is a YMMV situation, but has anybody else seen gross discrepancies between the real world in their garage and the calculator in the first post? Is it just a 5 volt thing? I know that many / most people use 12 volt pixels. I had high hopes for this calculator, but either I am doing some grossly wrong, or there is some fundamental math that isn't correct with the calculator.

    I visited a common Voltage Drop Calculator on the web. This one is so crude compared to the RGB Pixel Calculator, but I figured I would still make sure that V = iR https://www.calculator.net/voltage-d...=2.4&x=39&y=22 .... 18 AWG wire has a theoretical resistance of 6.385 ohms / 1000 feet... with 1.2 amps on the wire and 25 feet of wire length, that would generate a total voltage drop of 0.38 volts, which, from 5.0 volts is in agreement with the RGB Pixel Calculator of 4.6 volts... My question is, why are my real world pixels so different? At the Voltage Drop Calculator I just linked, if I change the wire gauge to 20 AWG, with the same 1.2 amps and total lighted length, I get a voltage drop of 0.61 volts, so 4.39 V, which is very close to my mean voltage stated above of 4.36 V. So I guess I should just assume that my pixels, which are advertised as 18 AWG are really 20 AWG?

    The problem I have now is that, I went back to the RGB Pixel Calculator and down-selected to 20 AWG wire and the voltage at pixel 50 suggests that it should be 4.5 to 4.6 volts, which is in disagreement with the Voltage Drop Calculator. With the RGB Pixel Calculator, I need to select more along the lines of 22 AWG wire for both the Pixel and Power details section to get the voltage to drop to 4.3 to 4.4 V. Is this a one conductor versus two conductor variance? With pixel strings, our voltage is dropping continuously along the pixel string to the end where I am measuring the voltage... and there are two conductors, one for voltage + and one for voltage -.

    I guess I'm curious what everybody else's experience is with the calculator? Anybody else use it for 5V pixels and achieve good agreement?

    Thanks for reading...

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