Power Supply help

christophe

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18AWG is 0.75 square mm wire. That's less than extension cords.
Look around in Aus for cable, the shipping for that is over the price of the cable.
Thank you. Extension cords carry 240V right. Thats why they have to be thicker. For 12V is 18 AWG too thin? Do you know where in Melbourne i can get the cables?
 

Dreamin

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I am after 3 cores cable so as to also run Data to the strips
I just bought some bunnings extension cords, which was cheaper per metre than per the meter stuff. Not sure if the online mini videos are up yet, but keith did an excellent one on power distribution and cable sizes and what no. It was really good and gave good advise about avoiding some cable types for good results. :) Worth a watch when it appears.
 

Mark_M

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Thank you. Extension cords carry 240V right. Thats why they have to be thicker. For 12V is 18 AWG too thin? Do you know where in Melbourne i can get the cables?
18AWG will totally work, although you might need more of it.
The Ray Wu stuff is not that thick for the price. The thicker the cable, the better. If you can get thicker cable for cheaper then that's the way to go.

An extension cord is 1 square mm 3 core cable. It may not always be in black but it's a lot cheaper than that.
Even cheaper is a roll of it from an electrical trade place.


I'm not even sure whether to post this next bit. It's about me using 18AWG wire from a power supply to the start of the pixel string. :rolleyes:. The bit afterwards is worse!
Spoiler content hidden. Log in to see this content.
 

christophe

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@Mark_M I found that online:

Do you think if i pair the power (2 wires), use 3 wires for negative and one only for data, will it work? With some research i came to this. Please correct me if i am wrong. Thank you
 
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Mark_M

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@Mark_M I found that online:

Do you think if i pair the power, use 3 cables for negative and one only for data, will it work? With some research i came to this. Please correct me if i am wrong. Thank you
Security cable does work to an extent but it is thin! It's about the gauge of Ethernet cable. It's about 24AWG (lower the better).

Using the current rating on the wire's listing, that's 28 LEDs per wire.
In parallel it's roughly double the current. 56 LEDs.
It'll be a messy amount of cable. My guess is a power injection point every 50 LEDs. About every 0.80m.
Over a 4m length it's 5 injection points. Not too bad...

Voltage drop across the cable is okay.... assuming it's 1m between the injection point and the power supply.
At 5m long you'd have 3v of voltage drop. That's already 25% gone.

I still think we can go bigger. Just because you can, doesn't mean you should.
And Keith's presentation showed how bad alarm cable was!

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I'd look higher.
 
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christophe

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Security cable does work to an extent but it is thin! It's about the gauge of Ethernet cable. It's about 24AWG (lower the better).

Using the current rating on the wire's listing, that's 28 LEDs per wire.
In parallel it's roughly double the current. 56 LEDs.
It'll be a messy amount of cable. My guess is a power injection point every 50 LEDs. About every 0.80m.
Over a 4m length it's 5 injection points. Not too bad...

Voltage drop across the cable is okay.... assuming it's 1m between the injection point and the power supply.
At 5m long you'd have 3v of voltage drop. That's already 25% gone.

I still think we can go bigger. Just because you can, doesn't mean you should.
And Keith's presentation showed how bad alarm cable was!

Spoiler content hidden. Log in to see this content.

I'd look higher.
Alright that makes a lot of sense. I will try to get 3 cores 1mm2 extension cable from bunnings then. I will go tonight to have a look and will confirm with you guys before buying the cables. Thank you

Also for the power injection, i will be running in total 165 led strips each 60cm. Therefore one strip will have on average 36 LEDs. I was thinking to power inject every 2 strips which will be 72 LEDs until the next power injection. Do you think thats good?

Also you added that from power supply to injection point it has to be as close as 1m. What if i my case, the cable sometimes will have to be run for 5m until the power injection point (PSU to Injection point=5m). Its only because i have to hide the cables and therefore thats why it has to travel 5m. What can i do to prevent voltage drop for these points? Or do you think i will be fine?

I am building a structure and running LEDs on it.

Again I would like to thanks everyone for their help
 

Mark_M

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Also you added that from power supply to injection point it has to be as close as 1m. What if i my case, the cable sometimes will have to be run for 5m until the power injection point (PSU to Injection point=5m). Its only because i have to hide the cables and therefore thats why it has to travel 5m. What can i do to prevent voltage drop for these points? Or do you think i will be fine?
By the distance between the injection point and the power supply, I mean the wire's distance. Over length the cable has a resistance.
The thinner the cable, the more resistance over distance.
This is how voltage drop occurs.


Also for the power injection, i will be running in total 165 led strips each 60cm. Therefore one strip will have on average 36 LEDs. I was thinking to power inject every 2 strips which will be 72 LEDs until the next power injection. Do you think thats good?
I'm going to hold back and ask what is the arrangement of these strips. Is this like a matrix?
Hi everyone, i am working on a project in my garage 4mx4m. I am running 6300 pixels ws2815 12V DC
I'm getting a little confused on the design of this prop. 4m x 4m using 165 strips that are 60cm?
Can you provide some context on what this is? Possibly a rough drawing?
 

djgra79

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My entire display is 4 core security cable. For power injection leads 2 cores twisted for +pos and 2 cores twisted for -neg.
For data leads 1 core data, 2 cores twisted -neg and 1 core +pos.
Works for me for both 5v & 12v.
 

TerryK

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... for the power injection, i will be running in total 165 led strips each 60cm. Therefore one strip will have on average 36 LEDs. I was thinking to power inject every 2 strips which will be 72 LEDs until the next power injection. Do you think thats good?

Also you added that from power supply to injection point it has to be as close as 1m. What if i my case, the cable sometimes will have to be run for 5m until the power injection point (PSU to Injection point=5m). Its only because i have to hide the cables and therefore thats why it has to travel 5m. What can i do to prevent voltage drop for these points? Or do you ...
Like Mark_M, I'm trying to understand this thread and getting confused. There are too many parallel and tangential questions to keep track of.

It's a minor issue but your 165 strips of 38 LEDs (average) calculate to 5940, not 6300. From what I've seen when I tested the WS2815s, power injection every 72 LEDs will be fine. I also do not think the 5m from the supply to an injection point is a problem. Wire gauge size and its associated voltage drop just needs to be considered.
Something not mentioned yet (I think) is, you had mentioned multiple supplies in different locations. The supply commons, typically the -V terminals, need to be tied together. A star arrangement works best, avoid a bus configuration. The problem with supply separation is it introduces ground loops; fundamentally, a voltage differential in the supply common.
 

christophe

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I am building a geodesic dome and having lights over it. With the amount of triangles, I will have to use 165 strips. And if I take 165 strips multiply by 38 (average), it gives 6270 LEDs in total. Please see attached picture for more clarification of the layout. I have also attached the cable that i saw in Bunnings and would like to confirm with you guys.

@djgra79 you said that 4 core security cable works fine for you. Do you think one like see below link, is fine?

@TerryK How can i resolve this issue of not getting voltage differential in the suppy common?
 

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TerryK

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Ideally keep your supplies in close proximity to each other and connect their -V terminals to each other with a fairly heavy conductor. If you implement the power injection strategically, that conductor will not carry much current and thus have little voltage drop within it. Its purpose is solely to reference all the supplies common terminal to the same voltage level (zero hopefully) and through the power injection cables keep the strings/strips DC- all close to the same voltage potential referenced back to the data lines of the controllers ports. This common connection should not carry any current. It may if there is a wiring mixup in power injection. This may mean having a longer 240AC cables to the supplies if they need powered from different AC circuits.

Others can weigh in with suggestions but I do not think the project is physically large enough to warrent mounting supplies in separate locations to keep power injection cables shorter.

For clarification:
I mentioned a star pattern, perhaps I should have used an 'X' to describe the structure where the angled bars of the X is the supply location and the injection cables fan out from there to the strips.
Voltage differential is a bit more encompassing term than voltage drop. Or voltage drop is nothing more than voltage differential between two defined points, power source to power consumption. One also should be aware that it happens in both conductors, the + line (current flow out) and - line (current flow return).

Looks like a nifty project. Please post photos when you get it lit up. Cheers.
 
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