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Topic: Large LED Array for Scrolling Sign (Read 758 times) previous topic - next topic

Kevin Hoyt

Hey all,

I haven't picked up an Arduino yet, though it tops the list of potentials.  I'm a software engineer but have never had my hand had hardware/interfacing.  This is an area I want to explore, so I've come up with a project that I think suits Arduino, but I'd appreciate some validation and pointers.

I'm sure you've all seen LED-based scrolling signs.  I've even seen some Arduino-based ones in my research.  I want to build essentially the same thing, but that covers most of my entire garage door.  I've measured the space and I'm currently thinking 38 columns by 16 rows, separated by 5 inches each direction, for a total of 608 lights.

While I've seen pre-fab LED matrix boards, I expect that this will be of my own creation (given the specific dimensions).  Can Arduino control 608 lights independently?  Would I need some additional controllers to manage all the lights?  Maybe break them down into smaller sections controlled independently yet coordinated to display a scrolling message?  How about powering the lights?  I'm guessing that would be done independently of the Arduino itself?

Any validation or pointers would be greatly appreciated.  Also, I've suggested LED, but would be quite happy cannibalizing strings of Christmas lights or the likes as well if it makes the project easier.  Have I bitten off more than I should for this first project?  

Thanks in advance,
Kevin

dcb

#1
Dec 28, 2008, 02:46 am Last Edit: Dec 28, 2008, 02:53 am by dcb Reason: 1
You can use a bunch of shift out registers ( i.e. 74HC595 )as far as I know: http://www.arduino.cc/en/Tutorial/ShiftOut

Then have shift out registers fan out and control other shift out registers till you have 608 pins.

I've never tried it though.

Edit: Example, if you have one chip control 8 chips controlling 64 chips then that would be 512 pins on the 64 chips, and 73 chips total, about $28 in shift register chips and a LOT of wiring :)

MikMo

I think attacking this problem in a modular fashion as you suggest your self is the way to go.  16 LED's in each coloumn is a good number, because you would be able to control exactly 16 LED's with 2 8 bit shift registers.

I would try to design a module with 2 8 bit shiftregisters and 16 LED's on a long "stip shaped" circuit board and add the required connectors to pass the signals on to the next module. Another important thing to take into consideration is power supply. How many LED's will be on at the same time ? how much power do they need ?  And how could you distribute power to all the modules.

The ultimate solution would be some kind of backplane with the power  and some connectors for each of the "coloumn modules", i think this is how the commercial signs are made.  This would be very flexible, since all the Arduino has to do is to shift out 16 bits for each coloumn, starting with the rightmost coloumn.

You should check the shift register tutorial in the playground.

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