Using Video Wall LED Panels
Some followup information on a recent discussion...
Chinese made video wall LED matrix panels is a well established industry, while being replaced in some cases by new large scale Organic LED and Micro LED panels, the traditional LED Matrix Panels still have their place.
Here is the 64x32 (2048) LED Panel recently demonstrated, that may be purchased for $17.88 with free shipping. https://www.aliexpress.com/item/32902068286.html
Using the industry standard HUB-75 interface and a 16/1 scan ( only 1/16 of the LED rows are on at any time) 1/5 to 1/32 scans are commonly used, with brighter, outdoor panels using lower scan divisions.
When used in large video walls these 4mm resolution panels are rated to consume about 500W per sq meter under typical conditions and up to 1200 Watts when displaying solid white (all LEDs on) this is something to consider before setting up a giant home video screen.
Here's an example of a flexible panel, costing about twice the price of a rigid panel.
The HUB-75 interface is a daisy-chaining scheme that requires the host to generate all of the PWM modulation of the RGB LEDs (unlike Neopixel and Dotstar "smart LED strings" that you can set and forget, these panels require a constant update. (Professional equipment typically uses FPGA chips to provide rock solid PWM timing)
The demo setup used a Raspberry Pi to drive the panel using a popular package.
https://github.com/hzeller/rpi-rgb-led-matrix
There are a number of projects on the web using this driver package, beware that Adafruit how to articles reference an older Adafruit specific copy of this library, your better off etting the latest thing.
I tried to follow a Hacker site how to article and got off track somewhere along the line.
Using the author's instructions on the Github page, I was able to install the software and run a demo with about 4 instructions.
He suggests A Pi should be able to drive up to 36 panels, although some users report noise an errors with more like 18 panels, if probably depends on how well one strips out Linux backround processors, for my single panel test I only turned of a couple things, like the HDMI audio.
The software author offers a level shifting board to make a more legitimate interface between the 3.3V Pi processor and the 5V matrix panel electronics, one can probably get away with a direct GPIO connection to a small string.
I ended up using the software compatible ElectroDragon board costing just $3 (buy a few items to get the per board shipping down to $1 ea). using the cables that come with the board, I only had to make 2 solder connections to the power supply to get it running.
https://www.electrodragon.com/product/rgb-matrix-panel-drive-board-raspberry-pi/
The board includes a real time clock, accessible if using only a single Hub-75 connector, the onboard Flash memory is not accessible by a Raspberry Pi 3.
Gerber file PCB design (Original? hzeller design)
https://www.seeedstudio.com/rpi-rgb-led-matrix-active-3-g-1068273
A Raspberry Pi 3A+ should work just a as well, the lack of an Eithernet connection can complicate the first software setup steps. A Pi Zero should work with electronic signage using a smaller number of panels, lower colors and less video. The driver software has the option to assign a dedicated core
to handle low level signals (this option is not available with the Zero and early Pis) One user reported getting good results using a TinyLinux that completely resides in ram.
Here's a demo playing a portion of the Raspberry pi screen? to a 6 panel matrix, driven with the ElectroDragon board.
I will add links to 12+ online projects using the hzeller software later...
While the standard Hub-75 panels using simple serial to parallel Constant current outputs to drive columns (with the host modulating the bit LED drive signal) there are new smarter chips with the same 24 pin layout as the original chips. These chips take care of the PWM modulation on board , reducing the host burdon, with up to 16 bit resolution, some have a randomizing factor that reduces the perceived flicker and anti-hosting measures. Some of these chips may have problems with the hzeller, although he makes an effort to keep up with changes in technology.
The original driver chip type is the JXI5020
(The Chinese market brands may have inferior performance)
One chip maker's comparision:
https://olympianled.com/jxi5020-mbi5024-mbi5036-tlc59283/
MBI5030, MBI5041, MBI5042, MBI5050, MBI5153, TLC5940 are examples of newer smart driver chips.
Here's a typical 0.5 x 0.5 meter die cast matrix assemble with internal power supply and quick snap together connectors, used for quick assembled rental video walls. Price is typically $500 each (Chinese shipping is also considerable) it is a lot cheaper to build a fixed installation.
Chinese made video wall LED matrix panels is a well established industry, while being replaced in some cases by new large scale Organic LED and Micro LED panels, the traditional LED Matrix Panels still have their place.
Here is the 64x32 (2048) LED Panel recently demonstrated, that may be purchased for $17.88 with free shipping. https://www.aliexpress.com/item/32902068286.html
Using the industry standard HUB-75 interface and a 16/1 scan ( only 1/16 of the LED rows are on at any time) 1/5 to 1/32 scans are commonly used, with brighter, outdoor panels using lower scan divisions.
When used in large video walls these 4mm resolution panels are rated to consume about 500W per sq meter under typical conditions and up to 1200 Watts when displaying solid white (all LEDs on) this is something to consider before setting up a giant home video screen.
Here's an example of a flexible panel, costing about twice the price of a rigid panel.
The HUB-75 interface is a daisy-chaining scheme that requires the host to generate all of the PWM modulation of the RGB LEDs (unlike Neopixel and Dotstar "smart LED strings" that you can set and forget, these panels require a constant update. (Professional equipment typically uses FPGA chips to provide rock solid PWM timing)
The demo setup used a Raspberry Pi to drive the panel using a popular package.
https://github.com/hzeller/rpi-rgb-led-matrix
There are a number of projects on the web using this driver package, beware that Adafruit how to articles reference an older Adafruit specific copy of this library, your better off etting the latest thing.
I tried to follow a Hacker site how to article and got off track somewhere along the line.
Using the author's instructions on the Github page, I was able to install the software and run a demo with about 4 instructions.
He suggests A Pi should be able to drive up to 36 panels, although some users report noise an errors with more like 18 panels, if probably depends on how well one strips out Linux backround processors, for my single panel test I only turned of a couple things, like the HDMI audio.
The software author offers a level shifting board to make a more legitimate interface between the 3.3V Pi processor and the 5V matrix panel electronics, one can probably get away with a direct GPIO connection to a small string.
I ended up using the software compatible ElectroDragon board costing just $3 (buy a few items to get the per board shipping down to $1 ea). using the cables that come with the board, I only had to make 2 solder connections to the power supply to get it running.
https://www.electrodragon.com/product/rgb-matrix-panel-drive-board-raspberry-pi/
The board includes a real time clock, accessible if using only a single Hub-75 connector, the onboard Flash memory is not accessible by a Raspberry Pi 3.
Gerber file PCB design (Original? hzeller design)
https://www.seeedstudio.com/rpi-rgb-led-matrix-active-3-g-1068273
A Raspberry Pi 3A+ should work just a as well, the lack of an Eithernet connection can complicate the first software setup steps. A Pi Zero should work with electronic signage using a smaller number of panels, lower colors and less video. The driver software has the option to assign a dedicated core
to handle low level signals (this option is not available with the Zero and early Pis) One user reported getting good results using a TinyLinux that completely resides in ram.
Here's a demo playing a portion of the Raspberry pi screen? to a 6 panel matrix, driven with the ElectroDragon board.
I will add links to 12+ online projects using the hzeller software later...
While the standard Hub-75 panels using simple serial to parallel Constant current outputs to drive columns (with the host modulating the bit LED drive signal) there are new smarter chips with the same 24 pin layout as the original chips. These chips take care of the PWM modulation on board , reducing the host burdon, with up to 16 bit resolution, some have a randomizing factor that reduces the perceived flicker and anti-hosting measures. Some of these chips may have problems with the hzeller, although he makes an effort to keep up with changes in technology.
The original driver chip type is the JXI5020
(The Chinese market brands may have inferior performance)
One chip maker's comparision:
https://olympianled.com/jxi5020-mbi5024-mbi5036-tlc59283/
MBI5030, MBI5041, MBI5042, MBI5050, MBI5153, TLC5940 are examples of newer smart driver chips.
Here's a typical 0.5 x 0.5 meter die cast matrix assemble with internal power supply and quick snap together connectors, used for quick assembled rental video walls. Price is typically $500 each (Chinese shipping is also considerable) it is a lot cheaper to build a fixed installation.
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