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Topic: Large LED matrix? (Read 3 times) previous topic - next topic

Grumpy_Mike

#5
Sep 01, 2010, 05:48 pm Last Edit: Sep 02, 2010, 12:12 am by Grumpy_Mike Reason: 1
So 10800 LEDs at 20mA per LED is a grand total of 216 AMPS!

Of course multiplexing cuts this down but it is still not a project for a single controller. Also 10800 LEDs at $0.2 is $216, it's an expensive project.

[edit]Sorry an order of magnitude out it is $2160[/edit]

deSilva

#6
Sep 01, 2010, 06:02 pm Last Edit: Sep 01, 2010, 06:34 pm by mpeuser Reason: 1
I have checked one or the other (around) 16x16 multiplexed  LED matrix during the last years.

They are dim! Even pulsing 50mA @ 1/16 of time will give you 3mA average only. Of course there had never  been pulsed 16*50mA = 1A into the matrix,. Let's assume half of the LEDs are shining (if you want to call it so...) and the driver would provide 200mA, then it's only 1mA per LEDs. That is exactly how it looks like!

So multiplexing should be limited to 1/8, to my experience.

This would still mean for the power:
1/2 shining = 5,000
40 mA pulses = 200A
1/10 multiplex = 20A = 40W

Note that you by no means should have current limiting resistors but need true constant current sources...


deSilva

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Also 10800 LEDs at $0.2 is $216, it's an expensive project.

Soldering one LED will take 30 seconds (I am a slow brazier :-) )
So I would need a full work week for it - also not cheap...

florinc

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10800 LEDs at $0.2 is $216

It would be more like $2,160. Very expensive.

HarvesteR

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It would be more like $2,160. Very expensive.


Yes, it's a big and expensive project... Thankfully I won't be the one paying for it ;)

I did the math, and everything rounds out to about 9 grand... quite a handful of cash, but this is supposed to be a commercial project, so this is actually pretty cheap, compared to what a full-blown LED screen normally costs, which is in the 6 figure range...

Anyways, my plan doesn't involve multiplexing... the idea is to split the matrix into manageable 20x20 modules, each with it's own Arduino Mega as a controller, and a master controller to feed data into them (or more than one, if a single Mega can't handle the data flow)...

So in the end we're looking at 35 Arduino Mega controllers and a 36th as the Master...  ;D

Each arduino will have it's own power supply, and there will be a 12v PSU for each module, so there shouldn't be any problems with astronomical current loads and all that...

Anyways, in the end the idea is starting to sound somewhat ludicrous with all these Arduinos and whatnot... So we're now looking to other options... namely a dedicated screen controller to drive all those LEDs... I mean, if a HDTV can do it with over 2 megapixels, and refresh 60 times a second, there should be some controller out there that can do it for a 120x90 pixel screen

I'm really no expert in any of this, so I don't know much about what can be done and what can't... I'm making this up as I go along...  ;)

Thanks for all the help so far  :D

Cheers

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