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Vince4xmas

Pixel watts at reduced intensity calculation

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I have several 50 count 12v pixel string rated at maximum string wattage of 36W.

I am reducing intensity at controller to run only at 30%. So the maximum string wattage is reduced to 10.8W.

Is the above correct?

If so, then I can use the 10.8W value to size my 12vdc power supply (plus, add 10% safety factor).

Example 16 pixel strings at 30% = 172.8W * 1.10 = 190W or greater 12vdc power supply.

Correct?

 

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Vince

I think the 30% is a pulse width, not an Amplitude (voltage) reduction .  Area under the curve.

I think if you run this for any length of time, you will kill the output filter caps due to very high current (recovery) swings.  This might take a toll on the whole PSU if continuously being hammered with these surges. My 400W external supplies were not that much more than the internal 200W (frame) models

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I would agree that it's not that simple.  You are going to need to measure a string at various intensities to know what the current is really going to be.  A lot of variables in play.

 

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Let me restate:

I have a 800 pixel mega tree and 270 pixel star. Pixels are all 12V.

Can I run all these pixels (1,070) off a 400W power supply if I limit maximum intensity on Pixcon16 to 30%?

Thanks

 

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Off hand, I doubt it, but you MUST measure the strings that you have to find out.  Power up one string and measure the current with all pixels at 100% white.  Then drop the percentage on all pixels and measure again.  I think you will find that it is not even close to linear.  Even if someone else gives a figure, you really need to measure YOUR pixels as they could be considerably different from someone elses.

 

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off hand I doubt it also.  PX draw draw some power even when dark. The chip in each node is always powered so as to receive data..

TESTING the actual load will give a better guesstimate than us sitting in front of  our MR displays. Wire, the actual strings (they need not be in final location, but the wires to them should be the ones used. I noted K6CCC has his up at the star, so all are really short (you could put the PSU down lower as long as you feed each bank with real copper 8Ga or bigger wire.) While monitoring VOLTAGE at a string, END, keep  turning on nodes until the voltage drops 10%  (test 1 is at 100% white. then repeat the test at your 30%. Now you have a profile)

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3 minutes ago, TheDucks said:

I noted K6CCC has his up at the star, so all are really short

Yep, my wires are three feet from the pixel controller to the first pixel.  Used 18 AWG SPT1.  For the wiring from the power supplies to the pixel controllers (about eight feet of wire), for 2018 I was using 12 AWG THHN in conduit.  That is smaller than I would prefer, but I was in a massive hurry to get it completed and it was about 2200 on a Sunday night when I wired it so I had to use what I had in stock.  It will likely become 8 or 10 AWG when I clean it up later this year.

 

18 minutes ago, TheDucks said:

While monitoring VOLTAGE at a string, END, keep  turning on nodes until the voltage drops 10%  (test 1 is at 100% white. then repeat the test at your 30%. Now you have a profile)

Better yet.  Repeat at several intensities (not just 100% and 30%).  That way you have a much better picture of what the load will be at various dimming levels.

 

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My wires from controller to first pixel are 12 feet (18awg) and my power supply resides in the same enclosure as the controller.

I will run the proposed test. Thanks.

Edited by Vince4xmas

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There should not be issues with the PSU to controller , then.  You will find it amazing how much voltage drop (%) there is on 18Ga at 12'.  If you can, set your PSU at 12.6 (13.2 is the top, but I stay away from the edges as a best practice)

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I do not use a Pixcon but on a few of my controllers I run over 1200 pixels at 50% using one 350w power supply with no issues at all. Most of my runs are between 12-20 feet to the controller. Each of my pixels are rated at .6w I believe

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Everything ran fine. 1,070 pixels at 12vdc with 400w power supply and pixcon16 intensity limit set to 30% max.

 

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