TLC5940 - 1st works, 2nd not :/

Hi all,

I'm stuck in a project.

Quick description:
I want to illuminate my desks.

I bought this 5050-clusters for that (18pcs):
Front & Back:

Common Anode, for 12V

I try to use 4 TLC5940.
Ch0 -> LED1-Red
Ch1 -> LED1-Green
Ch2 -> LED1-Blue
Ch3 -> LED2-Red
Ch4 -> LED2-Green
Ch5 -> LED2-Blue
...
...

5 "Cluster" on each TLC (Ch 16 not in use)

Look like this (Front & Back):

(Missing on picture: Cables to the LEDs and some soldering... but you get the idea)

Power:
The TLCs get the Power from the Arduino (5V), the leds by a lab-powersupply - 12V
Ground from power supply and Arduino are connected to each other.
All anodes are connected directly to the power supply.

Problem:
The 1st TLC works fine, doesnt get warm at all, just as it should be.
The 2nd TLC doesnt work at all

Doesnt get warm either, but the LEDs just dont light up.

For testing I used the "Basic_Use" Script from the TLC Library. I also edited the tlc_config.h (#define NUM_TLCS 2).

Currently there are only LEDs on TLC 1 & 2.

Can anybody help? Do you need more information?

Thx a lot in advance
Alex

There are some 2-wire components on that board? Are they the decoupling capacitors? (And if not
that could easily be why its malfunctioning). A more close-up pic would help with seeing if there's a wiring error.

I have no decoupling capacitors on (tut says its optional) but I got some here... could test that...

here are two bigger pictures:

http://www.sams.de/up/arduino-board/pr03-pcb-front2.jpg
http://www.sams.de/up/arduino-board/pr03-pcb-back2.jpg

Did you adjust NUM_TLCS in tlc_config.h and delete the existing Tlc_5940.o file so the change will take effect?

As I wrote in the beginning: Yes I edited the config.h

And there is no more tlc_5940.o to delete for a long time. (Since 2 versions?)

Oh snap.

So you why don't you have the SCLK connected between the chips? Each chip will need that signal.

Not clear on the purpose of the GSCLK but it seems that should be connected as well.

dammit.... i forgot to loop sclk and gsclk =)

why didnt I see that?

Chagrin:
Not clear on the purpose of the GSCLK but it seems that should be connected as well.

GSCLK is the clock signal that drives the chip's internal PWM counters. It won't work without it.

Du you mind me asking why you blocked the website address on the product ? is it a secret ? I would like to know who makes these LED modules, incase i want to buy some like those...

// Per

redbear79:
I have no decoupling capacitors on (tut says its optional) but I got some here... could test that...

I don't know what a "tut" is, but decoupling capacitors are not optional.

Given his status it's not surprising he's wrong about the capacitors.

I have no decoupling capacitors on (tut says its optional)

Sure it is optional. It goes with the option of if you want it to work or not.
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Where is the tutorial that made that claim? Can it be corrected?