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Topic: Controlling 360 LEDs with TLC5940's (Read 1 time) previous topic - next topic

njs707

Hi, I am making an interactive led table using ir sensors and emitters and 360 leds.  Each pixel is 4 " x 4 "  square, with a 3 x 3 led setup in each.  There are a total of 8 x 5 = 40 pixels in the table.  In this youtube video........   http://www.youtube.com/watch?v=K4HRXa-GxIk&feature=related   ...  he says that he only uses 1 led driver for all of those leds, how is that possible?  I thought, for instance with the tlc5940, only 16 leds could be driven?  Am I wrong?  I do NOT want to have to buy 40 TLC's for this project, please let me know.

Thanks.

email too at njs707@gmail.com

Grumpy_Mike

#1
Jun 14, 2011, 02:10 pm Last Edit: Jun 14, 2011, 07:30 pm by Grumpy_Mike Reason: 1
The trick is to multiplex them, but then you can't multiplex too much because you get dim LEDs and flickering.

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he says that he only uses 1 led driver for all of those leds, how is that possible?

Because that is not what he said. He said he uses only one CONTROLLER meaning processor NOT 1 LED driver.

CrossRoads

The LEDs seem to light up in blocks - maybe there just 1 output per block driving a transistor.
Will have to play with volume to hear the explanation.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Grumpy_Mike

He says that it is a four by four pixel grid, that takes 16 different LED drivers, that is how many you get with a TLC5940. Each pixel is a 3 by 3 grid of LEDs, that means for each output of the TLC5940 he is driving 9 LEDs at the same time. Also there is another TLC5940 to control the IR emitters for the hand sensors to pick up.

njs707

Well he says that one LED driver is for the white lights and the other is for the ir emitters, so it looks as if he only uses 1 led driver for all of those lights that light up, unless he has another circuit hiding under his setup which I doubt. And to be clear I am talking about the smaller of the two boards he is working with, the one that does NOT work well in external light.  But, is multiplexing, which I have sort of learned how to do here...
...    http://www.youtube.com/watch?v=lZyc6ulpkyM     ......  is it a good idea.. meaning could it in any way wreck my atmega328?  Is this guy's way good?  Id just do 4 x 4's using 8 pins, so I could control 32 LEDs with 16 pins.

Grumpy_Mike

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the one that does NOT work well in external light.

Yes he is on totally the wrong approach as to why that does not work, he thinks it is because of multiplexing time but it is not, it is due to sensor saturation. Anyway if you want to multiplex a TLC5940 the see this project:-
http://www.thebox.myzen.co.uk/Hardware/Mini_Monome.html

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