LED screen teardown, driving LEDs with video, mikeselectricstuff writes –
I just took apart a piece of the commercial outdoor LED screen that used to be in London’s Piccadilly Circus. Also included is a detailed analysis of the drive waveforms etc. which may be of interest to people trying to seriously use the 32×16 RGB modules
We carry 32×16 and 32×32 LED wall sections in the shop! Complete with Arduino wiring diagrams and libraries.
32×32 RGB LED matrix panel! Bring a little bit of Times Square into your home with this totally adorable 5 inch square 32 x 32 RGB LED matrix panel. These panels are normally used to make video walls, here in New York we see them on the sides of busses and bus stops, to display animations or short video clips. We thought they looked really cool so we picked up a few boxes of them from a factory. They have 1024 bright RGB LEDs arranged in a 32×32 grid on the front. On the back there is a PCB with two sets of dual IDC connectors (two input, two output: in theory you can chain these together) and 12 16-bit latches that allow you to drive the display with a 1:16 scan rate.
These displays are ‘chainable’ – connect one output to the next input – but our Arduino example code does not support this (yet). It requires a high speed processor and more RAM than the Arduino has!
These panels require 13 digital pins (6 bit data, 7 bit control) and a good 5V supply, up to 2A per panel. We suggest our 2A regulated 5V adapter and then connecting a 2.1mm jack Please check out our tutorial for more details!
Comes with: a single 32×32 RGB panel, two IDC cables, a power cable, 4 mounting screws and mini-magnets (it appears these are often mounted on a magnetic base)
Keep in mind that these displays are designed to be driven by FPGAs or other high speed processors: they do not have built in PWM control of any kind. Instead, you’re supposed to redraw the screen over and over to ‘manually’ PWM the whole thing. On a 16 MHz arduino, we managed to squeeze 12-bit color (4096 colors) with 40% CPU usage but this display would really shine if driven by any FPGA, CPLD, Propeller, XMOS or other high speed multi-core controller. The good news is that the display is pre-white balanced with nice uniformity so if you turn on all the LEDs its not a particularly tinted white.
Of course, we wouldn’t leave you with a datasheet and a “good luck!” We have a full wiring diagrams and working Arduino library code with examples from drawing pixels, lines, rectangles, circles and text. You’ll get your color blasting within the hour! On an Arduino, you’ll need 13 digital pins, and about 1600 bytes of RAM to buffer the 12-bit color image. At this time we do not have wiring documentation for the MEGA.
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