How to design 64x32 LED Matrix?

Using Arduino LEDs and Multiplexing
#1

I plan to design a 64x32 RGB LED Matrix and need some guidance from experts here…

  1. Project has to be extremely light-weight.
  2. Circuitry should be small size (excluding the Matrix)
  3. What Multiplexers, shift registers OR PWM I should be using.
  4. Should be cost effective but do not not want to compromise on size.
  5. Input Voltage <= 5V (as low as possible).

List of components would be great :slight_smile:

#2

Forgot to mention that each of RGB LED needs around 20mA.

#3

Hi amudliar and welcome.

Your requirements will not be easy, especially for a beginner!

What level of colour control do you need?

Have you looked for comercially available panels?

How about 2 of these? 32x32 RGB LED Matrix Panel - 4mm Pitch : ID 607 : $29.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Paul

#4

64x32 RGB is really 64x96, or 192x32, depending on how you arrange it, with either 3 anodes or 3 cathodes at every position.
I think I would go with 192X32, with common cathode RGB LEDs.
Use 192 anode drivers coming from 24 parts like cd74ac164, and some decent N-channel MOSFETs controlled by 4 shift registers for the cathodes. 192 * .02A = 3.84A, so you definitely want low Rds parts. Maybe even break the cathode drive section into halves.
http://www.digikey.com/product-detail/en/AOI516/785-1568-5-ND/3152480
Power dissipated in the part determines how hot it will run. P=IV, V=IR, subbing in you get P= IIR.
This one has .005ohm Rds, so would dissipate 3.843.84.005 = 73mW

With 32 columns, 24 Hz refresh rate, can leave each column on for 1/24/32 = 1300microseconds.
Use SPI.transfer to send data from arrays to the anode shift registers and cathode shift registers for fast updates and maximum on time per column.

CommonCathodeRGBLEDmatrix.png
CommonCathodeRGBLEDmatrix.png1464×677 14.6 KB

#5

PaulRB:
Hi amudliar and welcome.

Your requirements will not be easy, especially for a beginner!

What level of colour control do you need?

Have you looked for comercially available panels?

How about 2 of these? 32x32 RGB LED Matrix Panel - 4mm Pitch : ID 607 : $29.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Thanks @Paul. I plan to build it on my own using either 5050 or 3528 SMDs.
Paul

#6

CrossRoads:
64x32 RGB is really 64x96, or 192x32, depending on how you arrange it, with either 3 anodes or 3 cathodes at every position.
I think I would go with 192X32, with common cathode RGB LEDs.
Use 192 anode drivers coming from 24 parts like cd74ac164, and some decent N-channel MOSFETs controlled by 4 shift registers for the cathodes. 192 * .02A = 3.84A, so you definitely want low Rds parts. Maybe even break the cathode drive section into halves.
http://www.digikey.com/product-detail/en/AOI516/785-1568-5-ND/3152480
Power dissipated in the part determines how hot it will run. P=IV, V=IR, subbing in you get P= IIR.
This one has .005ohm Rds, so would dissipate 3.843.84.005 = 73mW

With 32 columns, 24 Hz refresh rate, can leave each column on for 1/24/32 = 1300microseconds.
Use SPI.transfer to send data from arrays to the anode shift registers and cathode shift registers for fast updates and maximum on time per column.

Thanks @CrossRoads. I have started looking into your recommended approach.

#7

CrossRoads:
64x32 RGB is really 64x96, or 192x32, depending on how you arrange it, with either 3 anodes or 3 cathodes at every position.
I think I would go with 192X32, with common cathode RGB LEDs.
Use 192 anode drivers coming from 24 parts like cd74ac164, and some decent N-channel MOSFETs controlled by 4 shift registers for the cathodes. 192 * .02A = 3.84A, so you definitely want low Rds parts. Maybe even break the cathode drive section into halves.
http://www.digikey.com/product-detail/en/AOI516/785-1568-5-ND/3152480
Power dissipated in the part determines how hot it will run. P=IV, V=IR, subbing in you get P= IIR.
This one has .005ohm Rds, so would dissipate 3.843.84.005 = 73mW

With 32 columns, 24 Hz refresh rate, can leave each column on for 1/24/32 = 1300microseconds.
Use SPI.transfer to send data from arrays to the anode shift registers and cathode shift registers for fast updates and maximum on time per column.

Started working on this and got few questions

  1. What difference it will make if I do Common Anode?
  2. In your above approach you are recommending how many MOSFETS? 32 I believe using 4 shift registers (Cathode connected)
  3. In the image attached (thank you!) I see you connected 6 pins to 2 LEDs (3 pins of each RGB LED) and since I need 64 LEDs. Does that mean I will need 32 shift register just to connect Anodes?
  4. What do you mean by 24 parts above?
  5. Is there a way I can minimize amount of components by replacing with ICs or something?
#8

Building a 192x32 matrix is no easy task, consider other options first, eg:

(just some WS2811 LED strips fixed to a board, can be built in half a day)

#9
  1. What difference it will make if I do Common Anode?
  2. In your above approach you are recommending how many MOSFETS? 32 I believe using 4 shift registers (Cathode connected)
  3. In the image attached (thank you!) I see you connected 6 pins to 2 LEDs (3 pins of each RGB LED) and since I need 64 LEDs. Does that mean I will need 32 shift register just to connect Anodes?
  4. What do you mean by 24 parts above?
  5. Is there a way I can minimize amount of components by replacing with ICs or something?
  1. With common anode, you need P-channel MOSFETs to source current, and parts like TPIC6B595 to sink current.
  2. 32, yes.
  3. 192/8 = 24 shift registers
  4. 24 shift registers
  5. Replace resistors with multi-resistor packs. See Isolated Resistor pack as an example
    http://www.bourns.com/data/global/PDFs/4100R.pdf
    http://www.digikey.com/product-detail/en/4116R-1-221LF/4116R-1-221LF-ND/1088628

Or, use strings as suggested, skip the multiplexing and send out (64x32)x(3 bytes/LED minimum) bytes of data to update the display using parts like WS2812, an integrated RGD LED/control chip.

WS2812.pdf (272 KB)

#10

You could try designing it is segments, using 8 Atmegas to drive 4 8x8 led matrices each, and linking them together with SPI.
Probably not the cheapest option, but easily scale-able up to any size, up to 127 modules (but that would take tons of power)

#11