Could anyone tells how to design RGB LED matrix ? - Page 1
Forum section: electronics / general

author: sangar
author_rank: Regular Contributor
timestamp: December 03, 2018, 04:30:43 pm
content: Hello All,I want to design 16 x 32 RGB LED matrix...I have seen some mono colour LED matrices and get to know how to drives it using LED driver likes STP16DP05...But, when you come into RG matrices, each LED has 3 pins for RGB...Here, each needs to be connected to each constant current sink channel of the STP16DP05 that have a total of 16 channels...Could anyone share your knowledge on this and give some guidance ?.Thanks,Muthu

author: tsman
author_rank: Frequent Contributor
timestamp: December 03, 2018, 05:00:01 pm
content: Easy route is just to use LEDs with an integrated control cihp like WS2812B or APA102.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: December 03, 2018, 05:15:17 pm
content: +1 for "smart" LEDs because: ease of use (µC or similar needed).To really give you a recommendation, more design parameters are needed.In case cheap 50/50 RGB LEDs suffice for all your needs in terms of brightness, size and color quality, you are good to go with those WS2812B and similar integrated "pixels".If your application is more demanding, other solutions like multiplexing with shift registers might be the way to go.Then, there are also products like these:https://www.adafruit.com/product/420https://www.adafruit.com/product/3649(also multiplexed with shift registers I guess)

author: sangar
author_rank: Regular Contributor
timestamp: December 03, 2018, 05:37:08 pm
content: Hi,Thanks for both...This is not going to be WS2812B design but the one adafruit have...I am trying to understand how Adafruit has designed 16 x 32 RGB LED matrix...Explanation will be appreciated...Regards,Muthu

author: tsman
author_rank: Frequent Contributor
timestamp: December 03, 2018, 06:05:34 pm
content: Those LED signage panels weren't designed by Adafruit.http://www.rayslogic.com/propeller/programming/AdafruitRGB/AdafruitRGB.htmexplains how the "HUB75" LED panels work.Long story short. It has 12x 16 channel LED drivers for driving the individual LED dies and a 3-to-8 decoder to select which portion of the display to connect to the drivers. 12 drivers x 16 channels per driver x 8 segments = 16 LEDs wide x 32 LEDs tall x 3 LED dies inside each package = 1536

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: December 03, 2018, 09:36:33 pm
content: There are also specialized driver ICs for LED signage with adjustable constant current capabilities.http://www.ti.com/lit/ds/symlink/tlc5916.pdfThe one linked above is an 8-channel type but you can get driver ICs for up to 144-channels. e.g.IS31FL3732A-QFLS2-TRDepending on your requirements these or similar might help you out.

author: sangar
author_rank: Regular Contributor
timestamp: December 04, 2018, 04:59:50 am
content: Hi Tusman,Sorry, I tried to delete one of the posts as soon as I made...But, "Remove" button was not working for me, then I left it as it is...Ok, coming to the things, I know that each RGB LED has 3 pins and they are R,G and B...Q1:These 3 pins needs to connect the three different channels of the LED driverQuoteQ2: Here, how they divide the full 16 x 32 RGB LED matrix so that they can connect only particular portion to drivers?Thanks,Muthu

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: December 04, 2018, 08:25:24 am
content: 1: Yes, every LED component (R, G, B LED) connects to one driver output.2: A 3-to-8 decoder can send a single input to one of eight different outputs via a three bit address (three address inputs).Output 1: 000Output 2: 001...Output 8: 111

author: sangar
author_rank: Regular Contributor
timestamp: December 04, 2018, 09:47:19 am
content: Hi,Thank you very much...I have one more question that I need to get 7000 lux when I lit all the 512 LEDs in white mode...I know that to get white out of RGB LEDs,I need to lit all the three...My LED datasheet says the intensity of R, G and B LEDs when If = 20mA as follows,R = 950 mcdG = 2100 mcdB = 480 mcdThis might seems a silly question:Q: Intensity of one RGB LED while it is white mode adds all the three intensity, 950 + 2100 + 480 =3430 mcd...Getting 7000lux in white mode is pass criteria for our LED board...Please suggest how to measure ...Thanks,Muthu

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: December 04, 2018, 01:33:41 pm
content: It is not that simple. For a white point of for example D65 you need a very specific ratio of R, G and B depending on the individual wavelengths of your chip.Here is an entry point:https://www.ledsmagazine.com/articles/print/volume-10/issue-6/features/understand-rgb-led-mixing-ratios-to-realize-optimal-color-in-signs-and-displays-magazine.html