i have a question for anyone more knowledgeable than i am…why would you need 48 separate resistors for this? i’m no electronics expert but couldn’t you just have one bigger resistor between the power supply and the led array?

also, as an addition to the project, it might be cool to put in an audio transformer and 1/8″ jack, so as to have the brightness be modulated by an audio source.

Posted at 2:24 pm on Sep 15th, 2008 by mattm

I used to build things like this years ago…something as simple as a row of five flashing LEDs can be quite hypnotic to watch, as they go in and out of sync.

@mattm: Firstly, you usually don’t need to include a current limiting resistor with flashing LEDs, as they usually limit the current internally (but you should check the
LED’s data sheet, as there are exceptions). If I recall correctly, you should wire multiple
flashing LEDs in parallel to achieve the above effect; if you wire them in series, they will
all flash at the same rate (as one of the LEDs will be switching everything in series with it on and off).

If you do need to limit the current of multiple LEDs in parallel, in theory, you could do this with a single resistor, but you’d need to ensure that it can handle the total power that all of the LEDs will draw. However, it’s usually not a good idea to do this, as the
electrical characteristics of diodes means that you can end up overdriving some of the diodes, burning them out, due to slightly different voltage drops across them, and the fact that a small increase in voltage across a diode can cause a large increase in current drawn. You should therefore include one resistor for each set of LEDs wired in series.

[Happosai]

Posted at 4:56 pm on Sep 15th, 2008 by happosai

thanks for the reply. that helped a lot!

Posted at 5:46 pm on Sep 16th, 2008 by mattm

I enjoyed your article. In regards to mood lighting check out the website…it currently offers a mood light system called Urban Underglow™. It transforms your room in to a chic mood light and glow experience. In May 2009 LIT will be launching a new LED system that will provide a full immersive experience integrating room LED lighting with your movies, games and other content! Imagine watching a movie with an explosion and your room lights up in red, yellow, orange all synched with the movie or your pc game. Or how about seeing the room glow in blue while watching an underwater scene in a movie or a pc game! LED lights (LED tubes, wall washers, etc.) are driven by the content you are watching!

Posted at 4:31 pm on Jan 28th, 2009 by mark Pohlkamp

Does anyone else have any experience with this?

Posted at 6:25 pm on Apr 6th, 2009 by George