24AWG wired Pixels from Ray Wu.

Yochui

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Dec 28, 2019
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It would depend upon the hardware you choose to use in your display. Power injection cable length will depend upon the number of pixels in a prop (or the number of pixels that are being driven by a particular cable if multiple injection cables are implemented), type of pixels (regulated or resistor), how hard the pixels are driven, and cable type (ohms per unit length, foot, meter, or whatever). I may have forgotten one of two but that's most of them I think.
Number of pixels and their drive level will determine the prop's amperage requirements. The type of pixel will determine allowable voltage drop although drive level plays into this as well. From voltage drop and amperage requirements the maximum length of a power injection cable can be determined based on a cable's resistance per foot rating.

An example may help. I'll fudge a few numbers as I do not have everything at hand presently. I have a Coro GE icicle, 3 actually but I'll use only 1 here. 150 pixels and I plan on using 5 volt WS2811s. Most individuals use .06A per pixel at 100% white for those but from testing I find them closer to .05A (I'll use .05A). From testing I also know that I cannot see anything above 90% which is still exceedingly bright so I'll limit drive for the prop at 80%. Amp requirement is then 150 * .05 * .8 = 6A.

Voltage drop is a bit more difficult to know but again from testing 5 volt WS2811s seem to start dropping in the 3.8 volt range (I'll use 4 volt). At this point the power injection cable needs to supply 6 amp with a voltage drop of no more than 1 (5 minus 4) volt. Ohms law can be used to determine the cable's maximum resistance (R = E / I) so 1 / 6 = 0.16667 ohm.
There is a 'got-cha' here that I feel a number of individuals overlook. Wire charts are not giving the ohms per foot of a cable but rather a single conductor within the cable. Voltage drop within the cable for the supply's negative run to the prop needs to be considered with the supply's positive run to the prop. Thus the 0.16667 above is negative and positive combined and needs to be halved. 0.08333 ohm is the value that needs used in the following.

I plan on using 14/2 which according to standardized charts has a resistance of 0.002525 ohm per foot. Maximum power injection cable distance is then the 0.08333 / .002525 = 32.6 feet. This would be for a single power injection cable. If I would run a 2nd cable and inject at the end then each cable essentially powers 75 pixels rather than 150 so the distance would double.

Apologies for the length; got carried away. I think there are no mistakes in all this. Cheers.
Hi Terry and do not apologize, I appreciate you taking the time to elaborate.
I am new to this and I love detailed information.

Thank you, thank you!
Josué.
 

Yochui

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Dec 28, 2019
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13
The panels I made are 600 * 2440 mm and have 150 leds. 6 runs of 25. I use 70 cm of 1.5mm square (i think 16AWG?). At the bottom every run is connected to the power injection wire. Every panel has its own psu.

A little video of 2 panels set aside
Hi Kockie!
Thank you for your new answer.

Your panel looks great. What's the spacing between each pixel?
I made the newbie mistake of purchasing a 70Amp PSU, and I only got 600 pixels so far, that I plan to run at 30%, for it will be an indoor tiny show this year.
I plan to buy several 20Amp to 40Amp PSUs, slowly in the following months to have larger, though modest outdoor show on 2021 (if 2021 does not bring any more surprises like 2020 has!).
 

Yochui

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Dec 28, 2019
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The spacing is 10cm in X direction and 9.6cm in Y direction. It was originally meant for a amateur musical play "joseph and the amazin technicolor dreamcoat", but corona postphoned it by at least a year....

Thank you Kockie.
I look forward to watching your show when it's done.
 

lithgowlights

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May 6, 2010
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Lithgow, NSW
The promotional pixels are all I use now and they are great, but you do need to understand that you need to power inject them EVERY 50 pixels. That power injection can be as simple as 2 wires from the point where you connect to the first pixel along to pixel 50, so that makes these ideally suited to higher density props like snowflakes, minitrees etc rather than outlines.
 

Yochui

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Joined
Dec 28, 2019
Messages
13
The promotional pixels are all I use now and they are great, but you do need to understand that you need to power inject them EVERY 50 pixels. That power injection can be as simple as 2 wires from the point where you connect to the first pixel along to pixel 50, so that makes these ideally suited to higher density props like snowflakes, minitrees etc rather than outlines.
Thank you Lithgowlights!
I understand. So I might give those promotion lights a chance.
 
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