It is just in the experiments I have tried then the dimming of multiplexing gets too much at values over 4:1. Even at this value the LEDs are not nearly as bright.
PWM while multiplexing is perfectly possible as long as the multiplexing is synchronises to the PWM.

If you are using the same current for each LED as you would if they were always on, that is absolutely true. However most LEDs can accept a much higher current at 1/8th duty cycle without burning out and can therefore be sufficiently bright. For example, The LEDs in my coat are rated at 30ma normally, and 80ma at 1/10th duty cycle. I'm currently pushing about 50ma at 1/8th duty and have had no issues. In fact, I have had to drop the max PWM level in my code in order to reduce brightness on some patterns.

That said, I do think that ischbe should be looking at the technical specifications for each component he intends to use. Instead of the uln2003, or FETs, you could easily use just the Shift Register and some sufficiently powerful NPN transistors. I used TIP120s, but that was mostly because I had them on hand and they can handle 5A.

It is completely doable. Just pulled my coat out again to do some testing and improvements on it.

http://rgbledcoat.blogspot.com/

Good day all and Hopefully I can be pointed into the correct direction. I tried using the search function but couldn't find exactly what I was looking for.

Currently my friend and I are trying to build a dancing light bar.  We have a RGB LED Strip, some TLC5940NT's and are slowly building this.  We got the TLC Chip via this tutorial to dance standard LED Lights.  However, we wish to move to highscale and do not wish to blow the Arduino.  I am wondering how we can push 12V via the diagram in the tutorial for these chips without hurting the arduino.

We wish to learn as much as we can on our own.  However, we are both Programmers trying to learn all of this.  

Check out this link. http://www.ti.com/litv/pdf/slva280
The transistor method is definitely less expensive but a lot more tricky, especially if you have RGB.

Although my guess is you've either fried everything or found a working solution :-P

I have been playing with the TLC5940 and noticed this as well. I have an 8x8 multiplexed RGB matrix with the 2 x TLC5940 on the negative leads, and a 595 shift register controlling the positive.

I'm not entirely sure what causes the dimness on specific pins of the TLC5940, however I was able to correct it by using 2n3904 NPN Transistors on the positive from the shift register. I believe that with the switching, I was not getting consistent current draw. I also made sure I was using a consistent voltage source as I ran into a number of issues attempting to just use USB power.

This significantly corrected the issue for me, I do not know if this would work in your case if you are individually adressing the LEDs.

I'm definitely curious about your Arduino Master & Processing code. I'm attempting to implement better control of my coat from a computer and wonder how you handled the bandwidth for that :-) I don't know if having an intermediary chip will be ideal, but I definitely am curious.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1285750833

hey dustmonkey..

I own a full Master Chief costume from Halo 3.  If you've never played Halo, its an exoskeleton suit like the one Iron Man has. Mine is really high quality..it cost me about 1000 dollars

Anyway I'm trying to use Arduino to build a shield system.  I don't know if you've ever played Halo 3 but when you get shot the whole guy lights up really bright all over..

I've been trying forever to find LED's at an affordable price that will run on DC power..  otherwise I need to wear a car battery and inverter and thats kindof insane.

How did you power your fur coat??

its awesome by the way

also if I managed to get the shields working would it be weird to wear something like that at that festival you mentioned?  like is it mostly just DJs or do people cosplay video games n stuff?

I would reccomend EL-wire for what it sounds like you would like to do as well. And pretty much all LEDs are DC powered :-)

Sparkfun has an EL-wire sheild which is pretty easy to interface with. That may be a good jumping off point.

I would also say that SeaCompression may not be the right venue for that, but just look up any gaming or geek convention (PAX, Sakuracon, Norwescon, etc....) in the local area and I think it would go over great!

For those in the Seattle Area, I will be at SeaCompression wearing the coat :-)

http://www.ignitionnw.org/seacompression

Absolutely fantastic, what reaction did it get at Burning Man?

I could barely walk 10 feet without being stopped, it went over incredibly well  

So, I just finished the writeup for a project I had been working on for about 3 months and since it was Arduino based, I am posting a link to it here:

http://rgbledcoat.blogspot.com/



The controller is an ATMEGA328p loaded with Arduino connnected to 6xTLC5940s and a 595 Shift register.

The code is running a modified version of the TLC5940MUX library to work with the shift register.
 http://www.arduino.cc/playground/Learning/TLC5940.

It took a lot of work to get any significant program to work as I was bumping into the 2k Ram overhead.

Hi Marklar,

I'm really curious how your code works for responding to sound. I currently have a working multiplexed array using TLC5940 & 595 Shift registers. I would just like to add some sound reactive effects to it and not quite sure how to approach it, any tips/code?