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Topic: what are the simplest and/or methods of controlling a 14 x 28 RGB led grid? (Read 76 times) previous topic - next topic

griffin175

I had a plan to use 19 TLC5940 with an arduino mega to control the grid of leds. obviously there aren't enough pins for all leds, so multiplexing was the solution. i could connect the anodes of the 28 rows into 4 groups of 7. But the code to control the TLC5940 is far too complicated for me. it wants 12 bits of data but bytes are only 8 bits, so theres some kind of correction i need to do. same for another pin that wants 6 bits. theres a way to work through it but ive tried and i cant understand the code yet. So is there another controller i could use? It would need to be 8 bits, constant current, and works for common anode leds. another issue is the mega might not be fast enough to control 294 leds at a time.
(392 Leds x 3 because RGB / 4 multiplexed)
and the last issue i have is that 25% duty cycle wont be bright enough. the matrix will be behind a piece of frosted glass and each led will have its own 1" box to light up. so if i could afford enough chips and control enough to run the whole matrix without multiplexing, that would be great. However, i could put more current into the led than its normally rated for. like 40ma instead of 20 to get it a bit more bright. but the TLC5940 will blow up sourcing 200ma at one time for all 16 channels, so the chip would need to handle the extra current.
So, what chip would you recommend? Should I us a faster controller like a Due? The Due only has 3.3v I/O pins, how would i deal with that?

griffin175

ADDITIONAL DETAILS: Would i be able to just toss out the controllers and multiplex the crap out of it so that i can run it all on the PWM pins? controlling mosfets and not directly of course. Im just worried about inconsistencies with brightness and every single cathode pin (1176 of them) would need their own resistor. could i work around that with some fancy circuitry?

johnwasser

I would use 14 rows of addressable RGB strip.  They have the PWM controllers built in and you just feed it data.  One inch spacing is about 40 per meter so the typical 30 or 32-per-meter spacing should be about right (just arch the tape between LEDs to make them closer together).  You'll need a little over 13 meters.  Some strips can only be split every second or third LED so you might get stuck with rows of 27 or 30 instead of 28.  You could always unsolder any extra. If you have any leeway in the design (spacing or quantities) I would recommend 14 rows of 30 LEDs spaced at the strip's spacing.  That way you'd get nice even squares.

You could also use NeoPixel LEDs.  They are individual units that include a processor.  It would require a LOT more wiring unless you design and make circuit boards that can act as an LED strip.
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BillHo


johnwasser

but you will get 16X32 grid
And it's only 71mm square so the LEDs would be spaced 0.25mm apart.  That's less then 1/10th the desired spacing.
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BillHo

The OP did not mansion the desired spacing, these will fit the desired spacing: FPCB board size: Width: 10 mm, thickness: 3mm



Wholesale 10- 1000pc WS2812B 5050 RGB LED &PCB Board 1-LED Module Pixel Light 5V

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