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A Giant DIY LED Display
smf28 writes "Dheera Venkatraman has created a giant DIY LED display featuring 36 blue Luxeons in a 6x6 array on the windows of Simmons Hall, an undergraduate dormitory at MIT famous (or infamous, if you wish) for its design. Recent uses included welcoming students in September, Pirate Day, and others."
oh god. mirror: http://web.mit.edu/dheera/www/simdisplay.php.html
I have some other examples of projects like this listed here. Very cool job by the MIT guys ... now they just need to add some more of 'em in all of the windows and provide the ability to generate alphanumber (or image) messages that can be uploaded from the Internet - heh, heh! ;-)
Hulk SMASH Celiac Disease
It is animated and scrolls text or any 6x6 animation; see the video on the link.
Fine use for any uC.
Check out Atmel AVRs. They're especially good if you've ever needed to do I2C and really didn't want to write a bit-banger system. They also have on-die oscillators, which could have removed the external crystal in their schematic.
~AVR Fan Boy
Make the array bigger and put Tetris on that thing, kind of like these guys or even these guys.
Many PICs have internal oscillators, but they are RC which isn't very stable, and def. not good enough for RS232 or any other communication - especially when the temperature of the room fluctuates a lot...
Oh, another thing. Do not put a resistor between the PIC and the MOSFET gate. Use a driver chip to translate the current levels. Cheap insurance.
You're kidding right?
A resistor for gate isolation is just fine, especially for a low side FET drive. A driver chip would cost as much as the FETs, and is overkill to the extreme. In a perfect world, where money and time are infinite for design, it's easy to make anything better. For something like this, a little realism is in order.
My $0.02 on the design:
I've done something similar as a proof of concept for a customer...256 RGB LEDs (50mA/color, ~38A at full bright/full white) with 64 custom processors controlled by a big Atmel. It ran off a standard 600W ATX supply, and it worked just fine, no voltage dropouts at all. I don't think the ATX supply itself was the problem, rather the layout of the circuit. A normal ATX supply has rather good transient reacitve capabilities. Using a single power supply for an entire floor is likely the culprit. It looks like the run on each floor was about 60', and I highly doubt that he used the right sized wire for that run (25A @ 60'-> #8). The accumulated coltage drop would be pretty extreme, making the PICs low voltage brownout inevitable. Combine that with an improper power supply arangement at each processor location and bam, crashes. The 6600uF caps are a band-aid, I agree. A fat wire feeding the high sides of the LEDs, and a secondary wire feeding the PICs would be my choice. Yes, they can safely be tied together, but ONLY AT THE SOURCE. That long run of wire will be all the isolation they need. Standard long distance bypassing at the PICs will keep them happy (10uF/1uF/0.1uF) and a nice fat ground return keeps it all under control. There were a few mistakes, but by no means is it fatally flawed.
This is not a sig. this is a duck. quack.
The Big Round Cubatron is a much bigger, much cooler DIY LED display. It was the cool thing at this year's Burning Man.
...well, you get the idea.
Videos here, here, here,
In 1995, Electrical Engineering students of Delft University of Technology did this, with playing Tetris on their 100m high building.t rum/90/english.html
t rum/95/english.php
e lco/matrixx/
Link: http://www.etv.tudelft.nl/vereeniging/archief/lus
In 2001, they used their building as a big SMS display.
Link: http://www.etv.tudelft.nl/vereeniging/archief/lus
In 2006, a huge 8x4x2m LED MatriXX was created.
Link: http://www.etv.tudelft.nl/vereeniging/commissies/