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I have a project Im currently busy with that I need a lot of help with.

What I want to do i create a flat 8x12 grid of LEDs and be able to control each individual LED independently from the others. I want to make "animations" for it (for now Im jut gona patch HIGH LOW through to the LEDs, but Im planning on making a full fledged program later on).

I saw guys on youtube creating LED cubes using the "column and row" technique, but Im not sure if that will work for me because I want to control each one independantly. Thats when my search led me to Shift Registers. Which will work best?

How would I manage the current for all the LEDs

Thank for taking the time to listen to a n00b like me :D

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  • i think you can drive them all from one GPIO, depending on the RGBs used; which?
    – dandavis
    May 10, 2017 at 9:06
  • Are you planning on buying a pre-made LED matrix, or making your own? That might affect the advice somewhat. Individually addressable LEDs are available but not (AFAIK) in matrices.
    – Mark Smith
    May 10, 2017 at 9:10
  • Probably going to buy individual LED and assemble them in a grid myself
    – Dewan
    May 10, 2017 at 9:16
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    In that case, I would suggest looking into addressable LEDs. Get it working once (Arduino libraries exist), no messing with external shift registers.
    – Mark Smith
    May 10, 2017 at 10:10

2 Answers 2

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You can control a grid of 8x12 LEDs using 8+12 (20) GPIO pins if your chosen board has that many. If it doesn't you can use a 3-to-8 decoder (e.g., 74HC138 - active low outputs, ideal for driving a P-channel MOSFET for the anodes of each row) to reduce that to 3+12 (15). You could cascade two of them and rotate the arrangement so it's 8+4 (12), though that's harder to do (although you can get 4-to-16 decoders too which would be simpler).

For multiplexing you don't want to use shift registers, they're too slow for smooth updates. You also don't want to drive each LED individually when you're working with that quantity, it just gets unmanageable and the power consumption would be excessive.

If you wanted to use shift registers you could use one (or multiple cascaded) to clock a single bit along them to select each row in turn. You could then reduce the pin requirement to 8+3 (clock + data + reset) though that gets a little more complex to program.

And yes, before you ask, you can address individual LEDs in the grid with multiplexing. You select one individual row (or column, but I'll just say row from now on) at a time and tell it which LEDs to light on that row, then move to the next row. This is why using a 3-to-8 decoder is good because it can only activate one row at a time which is what you want when multiplexing.

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There are a lot of ways to do what you want to do. Wiring them up individually would be one possibility those find a chip with that many pins can be a challenge

You can use shift registers, either statically or dynamically.

You can also use display drivers, like 7219 or the ht variants.

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End of the day it will depend on your application and constraints it has to live under.

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