[dorkbotpdx-blabber] Advice on large LED matrix

[dalas v.]

Thanks for all the advice. I'll try to be at the next meeting to pick your brain.

-dalas


--- On Tue, 12/9/08, Donald Delmar Davis <ddelmardavis at gmail.com> wrote:

> From: Donald Delmar Davis <ddelmardavis at gmail.com>
> Subject: Re: [dorkbotpdx-blabber] Advice on large LED matrix
> To: "A discussion list for dorkbot-pdx (portland,  or)" <dorkbotpdx-blabber at dorkbot.org>
> Date: Tuesday, December 9, 2008, 11:06 AM
> Dallas,
> 
> Because you have indicated that brightness is a priority
> then you are going to be looking at driving them in a row
> column fashion and the number of columns is going to be
> limited by the need for brightness. For around $13 per 8x8
> array maxim puts out a pretty clean solution which will do a
> lot of the work well. In the most people can afford it range
> you will be looking at shift registers and transistors
> sourcing the current and depending on the current of each
> led something standard sinking them like a 74x595/6 or a
> high current version of something standard like the tpic
> series of chips from ti. The need for light also more or
> less negates the other obvious solution which is to directly
> drive (through current limiting resisters) an array directly
> using the xxduino. The avr can source sink over 10ma  per
> pin but there is a cumulative limit which is in the
> electrical characteristics section of the fine datasheet.
> 
> I have purchased the parts to experiment with a circuit
> that was in Circuit Cellar a few months ago but I
> haven't had much time to lay out the boards so It wont
> be this year. In the interest of killing the thought you
> might look at several of the open source
> "products" out there for guidance..
> 
> Again we missed you yesterday.
> 
> Don.
> 
> On Dec 9, 2008, at 10:37 AM, dan p wrote:
> 
> > There is a way called Charlieplexing, the problem for
> your project might be brightness. The downside is that due
> to strobing the brightness is divided. If you need max
> brightness this sort of multiplexing isn't the way to
> go.
> > 
> > On Tue, Dec 9, 2008 at 10:05 AM, Mykle Hansen
> <mykle at mykle.com> wrote:
> > i'm interested in this question as well.  i've
> been told
> > that N shift-registers, combined with an arduino, can
> > control N^N or so LEDs.  but then a friend sent me
> this
> > article about how to control a small LED array with no
> > shift registers.  it only lets you strobe the LEDs one
> > at a time, but due to POV it can work, at least up
> > to some limiting size of grid.
> > 
> >
> http://www.instructables.com/id/How-to-drive-a-lot-of-LEDs-from-a-few-microcontrol/
> > 
> > i think someone actually showed me this at a dorkbot
> meeting
> > a month ago, and i recall staring at it and not
> getting
> > it at all.  but now i do.  a handy trick, for sure.
> > 
> > (there's another instructable linked from that one
> which
> > goes into the theory of this -- calling it
> "charlieplexing"
> > -- and it's a pretty easy read, for electronics:
> > 
> >
> http://www.instructables.com/id/Charlieplexing-LEDs--The-theory/
> > )
> > 
> > at any rate, controlling N output lines from one
> arduino
> > will be a recurring need for humanity.  if there are
> > other classic approaches with pros and cons, i'd
> love to
> > read a summary.
> > 
> > -m-
> > 
> > 
> > On Dec 9, 2008, at 12:16 AMTuesday, dalas v. wrote:
> > 
> > I'm thinking of building a matrix of RGB LEDs.
> Brightness is a priority. Size would be maybe 1 or 2 square
> feet. Battery power would be preferred, but if there is a
> need for AC power, I'd need to use a prebuilt power
> supply, because I don't want to attempt making one.
> Minimum control would be 32 color options (preferably more),
> maybe you can program 8 - 12 sequences and switch between
> them?
> > 
> > It seems like the arduino might be able to handle
> this? It would be my first arduino project. I know that it
> can control LED matrices and sequences, how would it be for
> a large matrix and how big / bright can I get?
> > 
> > I'm in the really early stages with this, so any
> advice or links to kits would be appreciated.
> > 
> > -dalas
> > 
> > 
> > 
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