First time mega tree

nicholas.buckler

nicholas.buckler

New elf
Joined
Dec 13, 2015
Messages
29
Hi All,

new to lighting up, want to get into pixels next year,


I think that I have drawn here Is correct for a 12v mega tree. 2 strings, 50 lights per run, with 20 runs,

Hints, tips, feedback appreciated - I think I should start the second string on the 11th run and connect the 2 negative lines where the new data line feeds in

Let me know

Mega Tee Wiring Diagram.png
 
Keep the negatives continued through the entire section where possible, i.e your data only line should have negative linking as well, linking the negatives at the power supplies is also a good idea.
 
My suggestion would be to consider using a few more controller ports for the tree. If you have an issue with a pixel it could potentially affect half of your tree functioning.

If you're set on using two ports, consider how difficult swapping out the pixels will be, and design your tree accordingly.

Speaking from experience here; my tree is a PITA to pull down to replace a pixel, so I just have to hope its reachable with a ladder. If not I have to put up with 1/6 tree out until I can find an afternoon to pull it down to fix.
 
@nicholas.buckler : A few thoughts, some which have already been mentioned by other ACL members.

If the 2 supplies are in close proximity to each other, say 1 to 2 meters or less, then it would be advisable to connect their V-'s together near the supplies. If spaced further then it becomes more debatable whether to directly connect them or not.

Some missing details make relative suggestions difficult; type of pixels, wire gauge size(s) both in the pixel strings and elsewhere, and pixel drive level. Those come to mind fairly quickly.

Power injection; do the injection points feed V+ upstream towards the controller or just downstream towards the string end? Fusing; while the fuses on the controller will protect cables controller to pixels, power injection cables ran direct from a supply should be fused; and depending upon lengths perhaps sub-fused. The 1st power supply, its cable "Y"s to 3 injection points. Is the AWG of the trunk portion heavier than from the split location to the pixel connections?
 
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merryoncherry said:
What kind of pixels are they? (I'm wondering why the complexity of involving a second PSU.)
Click to expand...
Hi

my calculations were that 1 psu may not be enough. That may be factory in using both sides of the falcon. I guess there is some future proofing in there too for when I have more pixels connected to the falcon
 
TerryK said:
@nicholas.buckler : A few thoughts, some which have already been mentioned by other ACL members.

If the 2 supplies are in close proximity to each other, say 1 to 2 meters or less, then it would be advisable to connect their V-'s together near the supplies. If spaced further then it becomes more debatable whether to directly connect them or not.

Some missing details make relative suggestions difficult; type of pixels, wire gauge size(s) both in the pixel strings and elsewhere, and pixel drive level. Those come to mind fairly quickly.

Power injection; do the injection points feed V+ upstream towards the controller or just downstream towards the string end? Fusing; while the fuses on the controller will protect cables controller to pixels, power injection cables ran direct from a supply should be fused; and depending upon lengths perhaps sub-fused. The 1st power supply, its cable "Y"s to 3 injection points. Is the AWG of the trunk portion heavier than from the split location to the pixel connections?
Click to expand...
Hi Terry.
Thanks for all your help. Regarding what pixels, this is an unknown. I haven’t purchased them yet. I guess ones I know the specks of the pixels I can made calculations for guage of wire etc
 
nicholas.buckler said:
Hi

my calculations were that 1 psu may not be enough. That may be factory in using both sides of the falcon. I guess there is some future proofing in there too for when I have more pixels connected to the falcon
Click to expand...
Oh, I completely agree that the Falcon should have a second PSU if using 350W PSUs. I was wondering why use both PSUs for the megatree... that would seem only necessary if using 12V regulated pixels at 100% output. 12V resistor pixels or 5V pixels, 1100 on 1 PSU is fine. One of my rookie mistakes was believing incorrect numbers about pixel current draw, and it led me to 2-3x more PSUs and ports than I'd really have needed, which also meant a lot more wires and setup time... just trying to spare you that.
 
I was always told you should always plan your show to run at 100% brightness. "oh, you only need one supply if you run at 30%" that gets thrown around a lot, I'm not 100% convinced this is safe and acceptable advice, unless you know what you're doing.

You're only one absent minded configuration change (forgetting to set at 30%, or having a voltage drop / pixel issues cause all your lights to turn on 100% white) overloading your psu/wiring.

LED Current – da-Share

www.da-share.com www.da-share.com

1669931774084.png

You're going to need 2 x 350W PSU's for 1100 12V pixels. Alternatively consider using a beefier 12V PSU, or even 5V for the tree (it's a dense prop and power injection should be fairly straight forward). Also remember that PSU's are only around 85% efficient.
1669931756089.png

I also find the spiker lights calculator handy for visualising voltage drop:

Whats good but also bad about this hobby (and something I did and still do struggle with in a way) is that there are many ways to achieve what you want to do, and everyone has a different opinion :)
 
franky_888 said:
I also find the spiker lights calculator handy for visualising voltage drop:
Pixel Light Power Calculator
Click to expand...
A good little site for figuring out the numbers.
But I think the visualisation is wrong. It should drop off fastest at the beginning, and then slow down as you get further down the line- which is the reverse to the way it is visualised on the site.

The reason being is that the current through the pixel wires decreases as you get further from the power supply as there are less LEDs to illuminate.
First pixel is carrying 100% of the load.
Half way through the string, it'll only carry the half the current.

As such, the voltage drop would be less as you get further down the line.
 
@Skymaster is right, this and other calculators assume the pixel can/will pull constant current current. 12V regulated pixels pretty much do (up to a point around 5-6V), resistors absolutely don't...

Which brings me to the question about whether 1 12V PSU will power 1100 12V pixels. If they are resistor it absolutely will power them at 100% and nothing bad will happen. The only way you'd get it close to max is if you had 12V to all pixels, which you won't due to voltage drop. If you've been a little negligent in power injection (as I tend to be) the 100% white number will result in lower volts and dimmer pixels rather than full current, which is kinda OK.

Common 12V regulators are another matter, they may use a half watt at 100% full and so 1100 uses 55A, well above the PSU's 29A rating, enough so that the LRS 350-12 would likely go into intermittent shutdown as it is spec'd to do. No damage, but a really poor show.
 
franky_888 said:
...d). Also remember that PSU's are only around 85% efficient.
...
Click to expand...
This doesn't really apply here. Generally a supply's efficiency deals with the power loss from the AC input side to the output side which could be either AC or DC. Once one gets to the output side, either in Wattage or Amperage, efficiency becomes a rather minor consideration.

@nicholas.buckler : What hardware have you purchased so far?
 
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