Rainbowduino Led Matrix / Resistor Question

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#1

Hello all :slight_smile:

Finally, my Rainbowduino arrived trough my German reseller :slight_smile:

So now i am eager to let it do its work.

I have some questions:

I am trying to solder an external RGB 8 x 8 Led matrix out of RGB-Leds, according to the wiring of the “small one” that you just plug onto the Rainbow.

Will this, at first, be possible at all if i stick exactly to the wiring provided in http://www.seeedstudio.com/depot/datasheet/2088RGBMatrix.pdf? I know that it takes a lot of solder-patience :wink:

Will i need resistors before every LED Colour channel, or does the Rainbowduino provide exact output?

I saw that the “small RGB-Matrix” does not need any resistors, and the wiring diagram does not show any also.

Thanks for your answers in advance

saw0, Germany

#2

No resistors are required as the LED driver chips have constant-current outputs. Yes it should work fine if you follow the wiring diagram. The rows go to “VCC” on the board and the columns go to “Red”, “Green”, and “Blue” obviously. The left column in the matrix is pin 8 on the Rainbowduino RGB connectors, and the top row is VCC pin 1.

#3

Thanks for your answer dave!

At least it saves me lot of additional solder-work, leaving out the resistors.

Any additional Hints which could save me a lot of time and headache?

Which Powersupply will i need for this 8x8 Matrix? Will a standard Nokia Charger work and provide enough power ?

TY

saw0

#4

You are welcome saw0. There was a bug in DispShowColor in the supplied firmware where the Blue and Red colours were transposed which confused us a lot when we were trying to get it to work with our homemade matrix. DispShowChar is fine though.

void DispshowColor(void)
{   
  unsigned char color=0,row=0,dots=0;
  unsigned char Gr,Bl,Re;

  // Bug: These seem to be mislabelled as they don't match the markings on the PCB
  // Colors in DispShowChar work correctly
  Re=(RainbowCMD[2]&0x0F);    // matches "Blue" on PCB
  Gr=((RainbowCMD[3]>>4)&0x0F); // = green, correct
  Bl=(RainbowCMD[3]&0x0F); // matches "Red" on the PCB
  RainbowCMD[1]=0;

See this thread for the power supply requirements, a 500mA power supply should be enough but more is better obviously.

#5

I am now palnning on ordering common anode Superflux LEDs.

Will common Anode work, or must it be common Cathode?

How could i switch the Rainbowduino to work with common anode Leds?

Thanks

saw0

#6

The Rainbowduino is designed for common anode, look at the matrix circuit in the “LED Devices Compatibility” section of the manual. I don’t think it would work with common cathode, as the M54564 would have to be working as a current sink rather than a current source.