I want to construct a very large 14 x 14 RGB LED matrix that basically hangs on my wall and is composed of 196 rougly 3" by 3" diffused glass squares. in front of an RGB LED. Design isn't my problem though. I'm a tech newbie and have no idea what parts to buy or what to wire (other than the LEDs and the arduino). If anyone can help with suggesting products/designing a schematic, it'd be most helpful.
you will need a way to power it all, and to handle that load well beyond the arduino's capabilities, ie led drivers or some simple 74595's and a pile of transistors ...
also you need to think how your going to address it all, which is more of a mental exercise
You should look out for a MAX7219. That can drive a 8x8 matrix of LEDs:
- connect to arduino via 5 wires (GND, VCC, CLK, LOAD, DATA)
- you set the current for all LEDs with ONE external resistor and dont need one R per LED
You basically send 2 byte command/data packages to the chip with shiftOut (or a manual implementation of that). For example you tell the 7219 to update Row X with 0x42. It then stores that value in its own memory and drives the appropriate LEDs itself without you having to do more.
Read the datasheet for more info.
Oops, i just saw you want to use RGB LEDs ... i think than you could just forget what i said..
Its not as bad as that.
Here is the start of a matrix.
There are 14 RGB LEDs across making 14 columns, and 14 rows of LEDs.
The Rows are driven from a set of shift register sourcing current.
14 rows x 3 LEDs/row = 52 output pins, 7 shift registers.
The Common Cathode of the 14 LEDs in column 1 are connected to an NPN transistor.
Same for column 2, 3,4 .... 14.
The Column transistors sink current and are driven from a 2nd set of shift registers.
14 columns = 2 shift registers.
So, the data for column 1 is shifted out for the 14 rows, and column1 NPN transistor is turned on, and then off.
the data for column 2 is shifted out for the 14 rows, and column2 NPN transistor is turned on, and then off.
Repeat for columns 3-14.
Power is not too bad, figure worst case is all LEDs in any 1 column are all on full at once: 14 rows x 3 LEDs/row x 20mA/LED = 840mA of 5V current.
