Arduino Uno, TLC5940 and CAT4201 how do I make them work?

Other Hardware LEDs and Multiplexing
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Skorn:
Hi Tristan,

I made some related comments recently in a thread regarding the "always on" issue with the TLC5940 here:

http://arduino.cc/forum/index.php/topic,144330.15.html

The PWM output on that chip can never be truly at 100% duty cycle, only slightly under. As youve figured out, the PWM is inverted due to the fact the chip is a current sink so the LEDs can never be fully turned off. If that is a manditory requirement to your project You'll need to modify your design. Four high level ideas I have off the top of my head are:

  1. You can have the microcontroller cut the power to the LEDs using a relay/switch of some kind.
  2. It should be possible to invert the 14 TLC5950 PWM signals using a transistor for each.
  3. You could implement LED drivers that use P-FETs to switch current.
  4. Do away with the TLC and Impliment a simpler design using a SoftPWM solution as I explain in the post I made in the thread linked above.

Hi Skorn,

thanks a lot for your input. First thing I'm trying now is via Darlington arrays according to your suggestion #2. But while waiting for the parts I'm going
to try the SoftPWM, sounds intriguing. And as you mentioned in the thread, reduces the amount of parts needed.

Greetings