[Lab] how to control several RGB LEDs with Arduino

Peter Sjoberg peters-modlab at techwiz.ca
Tue Aug 5 15:50:51 EDT 2014

Hash: SHA512

On 08/01/2014 09:36 AM, jslei033 at uottawa.ca wrote:
> My prefered chip is the TLC5940: it cam be daisy chained, you can vary
> each pin's brightness, and it controls 16 outputs at once. You can also
> use the WS2801 family of chips (some control one LED per chip, some
> control many LED per chip).
> You're on the right path, thinking of pwm extenders.
> The ws family is cheaper but the tlc are more heavy duty.

I guess it depends on how many LEDs you plan to control.
I was playing with 8x8 RGB matrix and for that I ordered DM163 and while
they arrived I haven't taken the time to play with it.
What I liked about it is that you can set constant current on each color
and it seems like the 8+6 is so that you set one for each individual dot
and the other for over all display light level.

from http://www.siti.com.tw/product/spec/LED/DM163.pdf

General Description
The DM163 is a LED driver that comprises shift registers, data latches,
8x3-channel constant current circuitry with current value set by 3
external resistors, and 64 x 256 graylevel PWM (Pulse Width Modulation)
function unit. Each channel provides a maximum current of 60 mA. The
grayscale data are separated into BANK0 and BANK1 respectively, selected
by SELBK pin. BANK0 is 6-bits grayscale data and the BNAK1 is 8-bits
grayscale data. Depending on the system requirement, both PWM banks
could be utilized jointly to achieve maximum 8+6 bit grayscale performance.
Alternatively, users can choose either 64-graylevel bank or
256-graylevel bank for dot correction, and the remaining bank as
image data. DM163 could also be constructed as a PWM controller for LED
drivers. When VDDH is connected to VDD, each of the 24 output channels
outputs can act as an inverse digital signal for controlling the LED driver.

* 24 Output Channels
* 8 + 6-bits PWM grayscale Control
* Constant Current Output: 5mA to 60mA
* LED Power Supply Voltage up to 17V
* VDD=3V to 5.5V
* Varied Output Current Level Set By 3 External Resistors
* Serial Shift-In Architecture for Grayscale Data

> On 14-08-01 8:59 Olaf Baumann wrote:
> Hey Lab,
> I got some RGB LEDS to play with but when I count the number of pins I
> need, it doesn't look like I can drive very many.
> The UNO has six PWM output pins and each RGB LED needs three.  As the
> saying goes, twos company, but I want a crowd!
> With regular LEDs, I used cascading shift registers to allow me to
> control 24 of them.  A great success in my temporarily blinded eyes.
> Is there an analog analogue to the digital shift register?  It seems
> that PWM is a hack for a voltage level, would a steady voltage be
> better?  SPI or I2C would be bonus--maybe I could use an ATtiny85.
> thanks,
> Olaf
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