GiulianoM;841704 wrote: One of the design features I wanted to implement was individual channel dimming control with the Meanwell LDD-H driver chips.
Since each LDD-H driver can accept a separate PWM signal, and each Dream Chip LED has 5 channels, for 3 Dream Chips that's essentially 15 separate LED strings to control.
The problem is that most Arduino boards, even the newest http://arduino.cc/en/Main/ArduinoBoardDue">Arduino Due</a> (my board of choice) only has 12 PWM output pins.
This meant finding a extra circuit board that could handle generating multiple PWM signals, and there are two chips that are popular for that:
<ul>
<li>[IMG]http://playground.arduino.cc/learning/TLC5940">Texas Instruments TLC5940</a> - This chip is a 16-channel PWM generator that can be used to directly drive small LED's (the small 2-pin round ones, not like Cree's).</li>
<li>[IMG]http://www.nxp.com/documents/data_sheet/PCA9685.pdf">NXP PCA9685</a> (pdf link) - Also a 16-channel PWM generator for small LEDs.</li>
</ul>
They both have mostly the same capabilities:
<ul>
<li>16 Channels</li>
<li>12-bit dimming (4096 levels of dimming!)</li>
<li>Daisy-chainable (connect multiple boards together - want 96 PWM outputs? 6 boards.)</li>
</ul>
However, the TI TLC5940 while popular has a crucial flaw - its PWM channels act as a [I]current sink</em> (negative or ground), and not a [I]current source </em>(positive).
The LDD-H PWM input requires a positive voltage of up to 6V DC, with a current source providing 0.1mA - a tiny amount, but still it needs to come from a [I]current source</em> and not a [I]current sink</em>.
The PCA9685 [I]can</em> provide the same capability as the TLC5940, and its PWM outputs can provide up to 10mA of current per pin - perfect!
It also has a PWM frequency of up to 1000 Hz / 1kHz - lights flicker at 60 Hz, so at 1000Hz the dimming will be super super smooth, in combination of 4096 levels of dimming.
You'll be able to dim at 1% without flickering.
TL;DR:
I'm going to buy one of these [IMG]http://www.adafruit.com/products/815">Adafruit PCA9685</a> driver boards to use for driving the LDD-H drivers.
The Arduino will control the PCA9685 board, which will control the LDD-H drivers... and let there be light. :)[/QUOTE]
Could you not use another due and use the I2C to talk to it and make a master slave?
