Arduino + TLC5940 + 3W RGB Leds

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello Arduinos,

I am working on a mood / party light project. The aim is to mount 16+ 3w star RGB leds radially into a board, stuff power + electronics inside and stick it to the roof where the normal lamp would usually hang.

The catch is that it is easy to drill a whole lotta disco balls to the roof, but you do not want to stare at those the whole week. This thing will go unnoticed (well until you turn it on :).

When turned on, the thing will then put a light show (or mood light) radially along the roof. The leds are dealextreme.com cheap 3w rgb stars.

The first problem is driving those leds sensibly as the TLC can only sink 120ma and it cannot do even that on all channels at the same time. I looked all over and did not find one good solution so I came up with one. What do you guys think? :

I am now driving the led with a transistor1 and a resistor. The base of transistor1 is driven by transistor inverter circuit. The inverter input is connected to the TLC out that also has a pullup resistor.

It seems to work!

Any better ideas? (cheaper->better, reliable->better, simpler->better).

I have a schematic and i'll try to figure out how to post it here.

If you have similar projects please post your ideas and experiences here.

Topics:
-TLC5940
-driving a large number of indipendent high power leds
-led optics
-programming the light show
etc...

Best Regards,

Tomas

2

It is difficult to know your exact circuit without a schematic. The problem with using the TLC5940 to drive another circuit is that you can get an inversion effect. That is off for the TLC corresponds to on for the LED when going through the drives. If that is the case there is a problem that while you can dim it you can't actually turn it off and the best you can get is very dim but not off.
This might not be a problem for you.
It would be good to post a schematic for others to be able to copy your work.