PLS HLP : TLC5940 - Y R all LEDs lit at same time

Forum 2005-2010 (read only) Software Interfacing
1

I'm attempting to test out the new TLC5940 I just got. I hooked up everything as described in the "basicuse" sketch, which is supposed to be a "Knight Rider" type effect.

The problem: all I get is that all LEDs are constantly lit pulling around 20mA across them a piece (with 2K ohms resistance between TLC5940 pin 20 and ground). There is no "Knight Rider" effect, or any variation at all.

  • I've double-checked the connections (not that that really means anything)
  • The Nano's surface mounted LED (which mirrors pin 13's output) is flashing very faintly and fast.
  • I've only attached 6 LEDs at the moment (see picture below) for fear of having 16 constantly lit LEDs frying something -- they are currently connected to pins 9 - 14 on the TLC5940.
  • Changing the value in the Tlc.set(channel, 4095) does nothing... nothing I seem to do with editing the code changes anything -- same outcome; all LEDs lit.

Also, I've read that some people say you should be sending +3.3V from the Arduino to the TLC5940 (instead of +5V)... how do I go about doing that with a Nano?!?!?

I've got to be doing something totally stupid... I know it! Any, and all suggestion/recommendations are appreciated. I'll post a pic in the next post.

Thanks so much for any and all help!

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Here's a pic of my current setup... only 6 LEDs are hooked up to OUTS 9 - 14 on the TLC5940. And obviously they are off right now since the USB cable is unplugged at the moment... thanks again!

1024×768 267 KB

3

OK... I fixed it... and YES it was a "stupid" mistake. I originally had interpreted the basic pin setup instructions as referring to the physical pin #s on the Arduino and NOT the Digital I/O pin #.

For example:

instruction excerpt: - digital 3 -> TLC pin 18 (GSCLK)

in this case I had TLC pin 18 connected to the Arduino Nano's pin 3 (which is RST) and I should have connected it to Arduino Nano's pin 6 (Digital pin 3).

If anyone else has this problem... here ya go.