Building giant LED walls comes with a serious set of challenges. Whether they lie in power, cable routing, or just finding a way to clock out data fast enough for all the pixels, it takes some doing to build a decent sized display. [Phill] wanted a statement piece for the office, so rolled up his sleeves and got to work.
The build uses P5 panels, which we’ve seen used before on a smaller scale. Initial testing was done with a Raspberry Pi 3, which started to run out of grunt when the build reached 28 panels. The refresh rate was slow, and anything with motion looked messy. At that point, a dedicated driver was sourced in order to handle the full 48-panel display. Other challenges involved dealing with the huge power requirements – over 170 amps at 5 volts – and building a frame to hold all the panels securely. Flexible Led Sign
The final product is impressive, standing 2 meters wide and 1.2 meters high. Resolution is 384 x 256. With a Mac Mini running video into the display through the off-the-shelf driver, all manner of content is possible. [Phill] even whipped up a Slack channel for users to send GIFs and text messages to the display. Naturally, we’re sure nobody will take advantage of this functionality.
If you’ve got your own giant LED wall, and you’re dying to tell us about it, make sure you get in touch. Video after the break.
Nice hack, but… 170A@5V is 850W of heating power. All of it for mediocre resolution of 384×256. 2×1.2m is quite a bit of display, but considering operational costs (electricity) and limited capabilities, I think I would rather spend more money up front on a big tv. Led walls make sense for really bug displays. Here.. it’s just a hack.
That’s exactly what my wife said when I proposed a 16×8 panel display at 2.5mm pitch in the lounge room for running cellular automata simulations and other coolness.
Incidentally, I had been thinking of a rewound MOT secondary for the 5V power supply, with a few extra windings on the primary to try and reduce saturation of the core.
I do not see why a 16*8 LED display (128 LEDs) should require a MOT for supply. That is less than 8A at 20mA/LED. 16m* 8m at 2,5mm pitch would be really big and power hungry. That would be even more than 4K resolution (6K). But in which house you have a 16m * 8m wall? Anyway, you do not really want a linear 5V PSU at a “MOT” level of power. I have an old linear 5V/30A (and several other voltages) PSU: “19 inch” frame and 30kg and the transformer has 9VAC nominal and more than double the size of a MOT. So half it’s power is wasted.
Get some switch mode PSUs
A MOT isn’t designed for long term high power. It is okay for minutes at a time like in an oven. Trying to rectify and filtering AC to 5V@170A is not easy as your caps need to supply enough energy for a large part of the cycle when the AC source is below the output. You are much better off having a higher voltage and step down with multiple localized DC/DC converter. Higher voltage means lower currents and the caps can also store higher energy. The localized supplies solves the high current power distribution problem.
> over 170 amps at 5 volts
No go! Not even for 5 minutes!
One PSU died when overloaded, it means it doesn’t have preper over-current protection. So running them at 94% load (170A out of 3*60A declared capability) seems a bit risky.
Wow. What pain. Nice of him to document it honestly.
I wonder what’s causing the apparent dot and horizontal bar artifacts. I thought it was just the video aliasing, but it’s in the stills as well. If those panels come out of the box behaving like that I’ll reconsider even harder buying those modules.
My 43″ TV is dying. Based on this video I’m going to skip over this LED notion and might just jump to that 70″ 4k display that Best Buy has on for $900 right now.
My guess with previous experience with LED panels and WS2812 strips, not having even enough power distribution throughout the screen. You cannot just drive power from the edges of a display like this, there is far too much voltage drop by the time it get to the other end. There is a reason the standard HUB75 display panels used in the LED jumbo screen industry are sized the way they are and have a heavy duty power connector on each panel. Each HUB75 panel at typical 16×32 or 32×64 pixels can easily draw a 4-6amps EACH with every pixel at full brightness white.
Think of that next time you see something like the LED screens at an event venue or times square. You are probably talking a potential power draw of 1000 or more amps at 5v or a large stage sized display.
An example of the power requirements, just look at something like this I came across on ebay a couple weeks back looking for HUB75 equipment. This thing appears to be using 16x32pixel panels in a 6×3 config. A whopping 96×96 pixels. The pictures of the open cabnet show the thing being driven by what appears to be 5 pretty standard off the shelf Chinese 200w 5v PSUs
https://www.ebay.com/itm/P10-outdoor-waterproof-cabinet-screen-for-advertisement-huge-led-video-wall/303102446170
The other thing it could be is the fact that these kinds of displays are multiplexed, only a single row per panel is lit at a time. Given the right camera shutter speed you will see the multiplexing. So even the insanely high power requirements these panels have could be multiple times worse if these things were something like an active matrix display where the rows did not have to be multiplexed and all the LEDs stayed lit all the time.
They are also wrong about the naming of these panels. They are not P5 panels. The industry standard for these panels is HUB75. P5 is the measurement of the pixel pitch. The number is the distance in millimeters between the pixels. Hence these are HUB75 panels with a 5mm pixel pitch
Aka P5 panels. HUB75 is assumed for all these panels, as its the only protocol used.
If only taptripco’s VCs really knew where their money was going…One gets the impression that this is ‘other people’s’ money.
170A@5V… I probably would have gone 5v@15A x 16.. Or something like that, with the power supply on the back of a set of panels. Smaller wires all around with nothing carrying insane current, and very safe with plenty of overhead.
Then again, if it was for my mancave, I’d probably just use whatever I could get to work too.
I have a cube shaped display that has 8 32×64 p5 panels. With a 60A psu and I’ve left it on full brightness white for over 24 hrs with no problems.
https://youtu.be/O2IuxPLIwEc
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