Hello from NZ

Xmas Beans

Xmas Beans

New elf
Joined
Mar 5, 2022
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Hi Guys. can someone please help me with some math for working out what PSU I need? its seriously doing my head in.
I am 100% new to this and am planning on working towards upgrading the strip on my house to proper 5v ws2812b.
However to learn and play I want to do a basic set up in my lounge of a 12 mtr run of 60led/pm ws2812b which runs at 18w/pm (when fully bright white)

maths is not my strong suit o_O Id like to run a Meanwell PSU if that helps. (NZ 240v)
I'll be using a Dig-uno by QuinLed as the driver.

an online tool has me calculated at 0.90A.. am I right that this means 9amps? if so a 10amp meanwell will be more than enough?

cheers for any help!
 
Last edited:
Xmas Beans said:
Id like to run a Meanwell PSU if that helps. (NZ 240v)
I'll be using a Dig-uno by QuinLed as the driver.
Click to expand...
Welcome to ACL @Xmas Beans !
Nice to have another kiwi in, we're slowly over taking the Aussies!

There is a Facebook group for NZ members. This is 'xLights NZ'. https://www.facebook.com/groups/600340247914353

I'm in the same boat finding power supplies in NZ.
WellForces is the only importer of MeanWell in NZ. I rang them a few days ago because their online system seems to be accidently adding tax twice.

In-true fashion, they never called me back.
I asked someone who has a trade account and they got a quote in less than I did within an hour.....
You can tell WellForces priorities on their trade customers.
 
Mark_M said:
Welcome to ACL @Xmas Beans !
Nice to have another kiwi in, we're slowly over taking the Aussies!

There is a Facebook group for NZ members. This is 'xLights NZ'. https://www.facebook.com/groups/600340247914353

I'm in the same boat finding power supplies in NZ.
WellForces is the only importer of MeanWell in NZ. I rang them a few days ago because their online system seems to be accidently adding tax twice.

In-true fashion, they never called me back.
I asked someone who has a trade account and they got a quote in less than I did within an hour.....
You can tell WellForces priorities on their trade customers.
Click to expand...
Meanwell are on Aliexpress my friend! other than my drivers I source everything via Aliexpress.
 
Xmas Beans said:
Meanwell are on Aliexpress my friend! other than my drivers I source everything via Aliexpress.
Click to expand...
Can't guarantee genuine Meanwell from AliExpress.
Mouser Electronics sells them for $70nzd with DHL shipping.

I'm looking for NZ seller for warranty and insurance purposes.
That way if there was an issue, insurance would chase the company in NZ rather than saying you bought it from over seas and we won't cover you.
 
Xmas Beans said:
60led/pm ws2812b which runs at 18w/pm
Click to expand...

Lets do some maths:

LED on Full White = 55mA = 0.055A
60 LEDs / metre = 60 * 0.055A = 3.3A
12 metres = 3.3A * 12m = 39.6A total

So, at 5V that would be 39.6A * 5V = 198 Watts

Xmas Beans said:
an online tool has me calculated at 0.90A.. am I right that this means 9amps? if so a 10amp meanwell will be more than enough?
Click to expand...

0.9A isn't 9A, it's a tenth of it - I'm not sure how the online calculator worked out 0.9A, that would be only 16 LEDs in your strip - not the 720 you've got there!

As for the power supply sizing, the recommended rule of thumb is not to load a power supply more than 80%
So that would mean that you'd want at least a 250W power supply (80% of 250 = 200W, right on the mark)

The "Go-To" power supply is a MeanWell LRS-350-5 for 5V work. This is a 300W PSU / 60A, which would give you some room to grow.
I'd also keep in mind that with those currents, you'd want to do plenty of power injection, you'd lose alot in the resistance of the strip very quickly. Every 2 metres would be a reasonable starting point.

The maths the other way also works:
12m * 18W = 216W
216W / 5V = 43.2A
They have used a value of 0.06A per LED to come up with the 18W/metre. The WS2811 driver doesn't drive them that hard (data sheet mentions 0.055A), so you save the small amount as calculated above.
 
Skymaster said:
MeanWell LRS-350-5
Click to expand...
Xmas Beans said:
Meanwell are on Aliexpress my friend! other than my drivers I source everything via Aliexpress.
Click to expand...
Mark_M said:
Mouser Electronics sells them for $70nzd with DHL shipping.
Click to expand...
$70nzd at Mouser for this model (I'm looking at the same).

To elaborate more on WellForces NZ...
WellForces NZ have issues on their site. $87 is shows then $100, then $115 on checkout.
Doing the maths on that, for some reason their system is adding tax twice.

meanwell.PNG
 
Mark_M said:
Can't guarantee genuine Meanwell from AliExpress.
Mouser Electronics sells them for $70nzd with DHL shipping.

I'm looking for NZ seller for warranty and insurance purposes.
That way if there was an issue, insurance would chase the company in NZ rather than saying you bought it from over seas and we won't cover you.
Click to expand...
Im ok with Ali, they are genuine, Ali is just cutting out the middle man. Im buying from a trusted supplier on there who many of the USA based pixel heaads buy off. :)
 
Xmas Beans said:
they are genuine,
Click to expand...
Got a link or seller name of these then?

A few Aussies on here have bought what was labelled genuine power supplies along with their pixel order.
They work fine, but placing a genuine one beside the AliExpress one showed many components and safety features not implemented.
 
Skymaster said:
Lets do some maths:

LED on Full White = 55mA = 0.055A
60 LEDs / metre = 60 * 0.055A = 3.3A
12 metres = 3.3A * 12m = 39.6A total

So, at 5V that would be 39.6A * 5V = 198 Watts



0.9A isn't 9A, it's a tenth of it - I'm not sure how the online calculator worked out 0.9A, that would be only 16 LEDs in your strip - not the 720 you've got there!

As for the power supply sizing, the recommended rule of thumb is not to load a power supply more than 80%
So that would mean that you'd want at least a 250W power supply (80% of 250 = 200W, right on the mark)

The "Go-To" power supply is a MeanWell LRS-350-5 for 5V work. This is a 300W PSU / 60A, which would give you some room to grow.
I'd also keep in mind that with those currents, you'd want to do plenty of power injection, you'd lose alot in the resistance of the strip very quickly. Every 2 metres would be a reasonable starting point.

The maths the other way also works:
12m * 18W = 216W
216W / 5V = 43.2A
They have used a value of 0.06A per LED to come up with the 18W/metre. The WS2811 driver doesn't drive them that hard (data sheet mentions 0.055A), so you save the small amount as calculated above.
Click to expand...
Big Thanks! ok I was pretty close then, I'd worked out the 250w bit xD and was looking at that exact LRS-350, thinking - if the math checked out - that I could add a 2nd strip later on.

Yes re Power Injection! I have that sorted and yes the intention was to PI every 120 nodes 👍

Thank you for your assistance! the PSU was the last piece of the puzzle that I couldn't wrap my tired brain around.
 
Mark_M said:
Got a link or seller name of these then?

A few Aussies on here have bought what was labelled genuine power supplies along with their pixel order.
They work fine, but placing a genuine one beside the AliExpress one showed many components and safety features not implemented.
Click to expand...
Mean Well China Store. sold via Amazon (usa) and aliex

Wellforces are using the exact Imagery, ali appears to only be about $20nzd cheaper than the prices in your images (excluding the tax issue) totally get the insurance angle however.
 
Welcome to the forum

You'll probably find that 60 LEDs per metre is more trouble than it is worth. This is alright because you're just doing a small-scale test. 30 LEDs per metre is plenty and you might even want to run that below 100% brightness. Assuming that you keep the brightness setting the same, increasing the pixel density will increase the power injection requirements and the number of power supplies that you need.

Do you know about power injection? You'll need it if you want to run a continuous 12-metre length of 5 volt strip.

If you're able to get the MeanWell RSP-320-5 at a similar price, I'd recommend that instead of the LRS-350-5.
 
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