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Most cost-effective way of addressing thousands of bright LEDs

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I am at the beginning of a design, which I hope to have ready for Christmas. In principle it is simple, in practice it is a bit of a headache already.

I need to program a microcontroller, a PIC in this case, to flash >5000 bright LEDs in sequence of predetermined combinations.

The number of predetermined combinations is large (>1000) so unless there is a particularly efficient way of using the memory of a PIC, I will probably need to include some form of external memory so that I can transfer the data from a PC to the device in its entirety.

My first thought is to use a PIC to supply data to some yet unknown arrangement of multiplexers, which will then flash the LEDS, via transistors once in each predetermined manner.

The design should be able to flash any number of LEDs at once, or in tight succession if this helps make more efficent use of the batteries and hardware. Batteries might be any number of AAs.

The LEDs might be pulsed with current above their specification, for extra lumens, briefly and infrequently considering that each combination will be different from the last.

One possible way I was thinking about would be to have multiple levels of multiplexers to account for the many independent outputs, but when you consider the software complexity of controlling LEDs through a number of layered multiplexers it might be more convenient to design the software to replace a layer or two, especially since the LEDs of each combination may be flashed in rapid succession.

Ideally I want each update to be as quick as possible. I was thinking that the problem might be in some ways similar to addressing pixels on a TFT screen. Does anyone know if there is a really good way of accomplishing this sort of task?

Thanks in advance!


By the way I had also thought of having a master-slave setup with multiple MCUs, but for that number I would need many MCUs. The number of LEDs is so large that I would still need some other method realistically....

maxim has a nice application note on large led displays. (see .pdf attached)

i believe mikeselectricstuff on the forum here is an authority on the matter.

Okay, I don't want to be a wet blanket but back up a second ...

">5000" ... "any number of AA batteries"

Say that worst case only 10% of the LEDs can be on at the same time. That's 500 LEDs.
Presuming an average of 20mA per LED, that adds up to 10 AMPS.
You need to be considering a car battery, not AA cells.

Suppose, God forbid, you want all 5,000 on at the same time ... that's 100 amps.
Now we're talking a couple of golf cart batteries to get any run time out of the thing.

Sure you could mux them, but you'll take a big hit in brightness.

What's more, you said bright LEDs which could easily draw much more than 20Ma depending on the device.

I think you need to do a little power budgeting  before diving into what are going to be some serious computer horsepower issues.


--- Quote from: sonicj on October 27, 2010, 04:25:26 am ---maxim has a nice application note on large led displays. (see .pdf attached)

i believe mikeselectricstuff on the forum here is an authority on the matter.

--- End quote ---

Thanks for that. Any help is great. Going through it now!


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