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Topic: My RGB LED Stairs Illumination video (Read 21 times) previous topic - next topic

Cranium


are you addressing each RGB Led pin separately?


Yes.  The 3 boards below the processor board are addressing each of the colors and each has 30 pins for each LED (2 on each step).  I could have used multiplexing to reduce the number of TLC5940s, but the wiring would have been the same so I decided to ensure maximum brightness by driving each separately.

The processor board also provides the +5V pin headers for each of the LEDs.

funkyguy4000

I'm assuming that the led pins are all in a paralell circuit, right?
Otherwise what are you using to power the whole thing?
Accelerate to 88 miles per hour.

Cranium


I'm assuming that the led pins are all in a paralell circuit, right?
Otherwise what are you using to power the whole thing?



Not sure as to exactly what is meant by having all led pins in a parallel circuit but the circuit design uses 6 TLC5940s that are in series.  The data out for the first drives the data in for the next and that data out drives the data in for the next and so on...

The first two TLC5940s drive the red, the second two drive the green and the last two drive the blue.

I used this library for the control of the TLC5940s: http://code.google.com/p/tlc5940arduino/

Peak amperage that I saw was about 1.4A at 5V and I am using a 7.5V, 2.5A wall wart as a power supply.

funkyguy4000

Well i mean a series circuit is, for example, having leds one after another on one line of power.  Where as a paralell would be more having 1 led part off into its own line and then reconnect.

Here

http://people.sinclair.edu/nickreeder/eet150/PageArt/SeriesParallel1.gif

R2, R3, R4 are all in series although R1 is in a paralell circuit with the other resistors.

Are you using any capacitors on your project?
Accelerate to 88 miles per hour.

Cranium


Well i mean a series circuit is, for example, having leds one after another on one line of power.  Where as a paralell would be more having 1 led part off into its own line and then reconnect.

Are you using any capacitors on your project?


Gotcha.....the control circuit is series but the LEDs would be parallel.  Each is individually powered and sunk to its own pin on the TLC5940.  Yes, I am using capacitors.  A 100nf and 10uf capacitor worked fine in breadboard but then when I powered the breadboard from my wall wart and 5v regulator, it had issues so replaced a couple 100nf with 1000nf and no more issues.  It would have likely worked with just the 100nf once everything was on PCB because another noise issue on the breadboard causing intermittent flickering went away as well.

The VR I'm using is rated at 1.5A so I am pretty much peaking it out.  When I used a 12V power source, it got over 300°F and went into thermal shutdown which is why I started using the 7.5V power source.  If I run all the lights at maximum brightness (RGB on each LED) for an extended period of time, it will still get pretty hot but won't go into thermal shutdown.  But since I'm not ever running at full power but for brief transitions, and most of the time it is well below 1A, it only gets slightly warm.  I'm still putting small fan in the box it will reside in just to be on the safe side though.

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