Controlling multiple RGB LEDs

I have not used this with the Arduion, but have used it in may other projects.  But the MAX7300 (I2C) or the MAX7301 (SPI), coupled with some ULN2003 if needed and drive 28 more I/O ports.  It's called a Bus Expander, It can be configured as an input or output.  NXT also has some port expander IC's that can do the came thing.

Regards,

Dave M.

You can use a MAX7219CNG serial LED driver, it will interface with an Arduino using only 3 I/O pins and only requires 1 resistor to set the LED brightness, it can directly control up to 64 LEDs.
They are available at most of the elecrionics suppliers but you can get them cheap on ebay.

Peter W.

Would such logic also be applicable for LED moving message signs? I have always wanted to make my own!!!

Regards

Andy

PS. I am not trying to takeover the blog, just possibly add wider interest.

If you daisy chain the Dout from one driver to the Din of another driver you can drive as many LEDs as you want using only 3 I/O pins on the Arduino.

2 x 5 x 6 x 3

2 x 5 x 18

multiplex them  ::

2 x (5 + 18)

2 x 23  ,   with a bit of double fancy multiplexing, that last bit could select between Array1 and Array2 using complementary transistors: NPN and PNP

1 x (24-bit  I2C I/O EXPANDER)

1 x TCA6424A     < $3.00 at some suppliers.

Although, I think it is possible to regroup them so you still only need ONE IC.

2 x 6 x (5 x3)  =>  2 x 6 x 15  =>  2 x (6 + 15)  =>  2  x 21  =>  2 + 21  =  23 pins

   For the blinking to be unperceived, F > 40 Hz or 25ms.   Therefore, each individual 'row' must be turned on for a maximum of 25ms/12 = 2.08ms which just happens to be a great deal larger than my rough estimate of the I2C maximum refresh rate for that chip of 123us with its 400kHz bus.    POV is easily achieved.  Note: I would be doubtful if you were attempting 4 Arrays of that size with RGB LEDs on a single I2C bus.

only 5x3 LEDs (a single rgb row) will be on at a time!  and reduces the size of your power supply requirement to about 500 mA !

You are right 30 RGB LEDs would be 30 x 3= 90 LEDs, so you would need two MAX7219EWGMAX7219EWG driver chips to handle them. If TCA6424ARGJRTCA6424ARGJR chips were used you would need a separate resistor inline with each LED to limit the current, using a chip designed to drive multiple LEDs like the MAX7219EWGMAX7219EWG only requires one resistor per driver IC to set LED brightness.

Was it established CA or CC?    2 arrays of 30 is only 60 LEDs; 60 x 3 (r/g/b) = 180.  Ok, yes,  I guess a dollars worth of resistors would be required.  People expect to see them on the board and they look cool.    If you want to hide them use SMDs.

I am pretty sure only one resistor per expander I/O pin is needed; so that is 24 resistors.  Please also note that if the R, G, and B need different currents for equal lumens then it is a simple matter to change the value of the resistor for that color in each 'column'  on the associated expander i/o pin.  That is an important issue as you can see from this data sheet for these RGB LEDs.

Each column is wire OR'd together.  Each row's Common Anode/Collector is wire Or'd and contolled by base of transistor to Vcc/Vdd as required.

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

rgb rgb rgb rgb rgb        rgb rgb rgb rgb rgb

Hey, I am new to this.  I have not built one of these, but plan to this year.

If I have missed something or made a mistake.  I do not mind hearing about it.