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Author Topic: Opinion on 2D, Single Color LED matrix sizes  (Read 1100 times)
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I would like to know what people think or know is the largest LED matrix, 2 dimensions (but set up like those 3-dimensional LED cube matrixes) that could be powered by an Arduino Uno OR that could be controlled by an UNO, but powered externally.

We have an "No Vacancy" sign here at the motel that currently does NOT work.  Its neon and every attempt we have had to fix it (its the power supply) has failed.  I was thinking we could replace it with an LED setup.  Here are the dimensions of the unit that the LEDs could go inside of.

10-inches tall by 38-inches across.  THe box that houses the sign is double sided, and is about 1 foot from front display to rear display.  Not sure about weather resistance, but it does rain and snow here and it could always be retrofitted to deal with that.

How many LEDs (overall density) could I pack into the sign box and how many arduinos (with the needed shift registers, etc) would be needed to handle all of this.  I would also need wireless control, preferably via Wifi, for turning it on and off, and toggling the display of "Vacancy" and "No Vacancy"
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In theory, a matrix of 8 x 80 LEDs should be enough to display "No vacancy" with a pretty good character definition.
Even with normal LEDs (20mA), the sign should be visible from at least 20 meters.
With such a sign you could do a lot more than statically displaying "No vacancy", for example scrolling longer messages, displaying time, temperature etc.
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yep, thats exactly my thoughts.  Whats nice is that there are two boxes that could house matrices, one would act as the No Vacancy sign, the other as whatever else I wanted to display.

8x80 LEDs would be 640 LEDs for a single side.  Since these signs are dual-sided, that would be 1280 LEDs.  I am guessing I would need to have multiple Arduinos or secondary controllers to operate and power the displays themselves (LED driver of some kind), and I understand the mechanics behind matrices (turn on and off the rows and columns of the matrix at rates faster than the human eye can discern, creating the illusion of a solid image).  Any suggestions on back-end hardware?

I looked a little into RGB LED tape/ribbon, but am unsure if I could get the density to work out.
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Start simple. If you're just replacing a "(NO) VACANCY" sign, you do NOT need a full matrix grid, and you do NOT need any shift registers! Just wire up two independent LED circuits.

One circuit controls all of the LEDs in the pattern for "NO".
The other circuit controls all of the LEDs in the pattern for "VACANCY".
You don't even need a microcontroller-- two toggle switches will activate/deactivate the necessary driving transistors of the above circuits. Total parts cost probably under US$50 including the AC-DC adapter (find a computer repair/recycling shop, they always have bins and bins of random DC supplies for almost free)

This way you can utilize your space and LEDs more efficiently. A 8x80 matrix that only displays "VACANCY" will have about 50% of the LEDs that simply are never utilized because they represent black parts of the text. Basically I'm suggesting that you use LED ribbons to mimic the neon you're replacing. Less control-ability, but it will be brighter because you're not scanning the display (8 row display will have 1/8 duty cycle)

Obviously if you want to display other text, you'll have to go for the multipurpose 8x80 matrix and all the multiplexing that manages it.
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Start simple. If you're just replacing a "(NO) VACANCY" sign, you do NOT need a full matrix grid, and you do NOT need any shift registers! Just wire up two independent LED circuits.

One circuit controls all of the LEDs in the pattern for "NO".
The other circuit controls all of the LEDs in the pattern for "VACANCY".
You don't even need a microcontroller-- two toggle switches will activate/deactivate the necessary driving transistors of the above circuits. Total parts cost probably under US$50 including the AC-DC adapter (find a computer repair/recycling shop, they always have bins and bins of random DC supplies for almost free)

This way you can utilize your space and LEDs more efficiently. A 8x80 matrix that only displays "VACANCY" will have about 50% of the LEDs that simply are never utilized because they represent black parts of the text. Basically I'm suggesting that you use LED ribbons to mimic the neon you're replacing. Less control-ability, but it will be brighter because you're not scanning the display (8 row display will have 1/8 duty cycle)

Obviously if you want to display other text, you'll have to go for the multipurpose 8x80 matrix and all the multiplexing that manages it.

Very good suggestions.  I believe I will go this route for the No Vacancy portion.  What kinds of RF devices are there for doing wireless control.  I know of the XBee and how it can be setup to work without an Arduino or other microcontroller, but the XBee may be just a bit too much for a simple on/off.  Actually, I wonder if I could take apart and use the RF system of an RC car.
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then again I may just use an XBee since I have other project ideas in mind that could use them too, so having a couple of them to get used to using them would be a good thing.
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Another option, maybe cheaper and requiring less work, is to use 2 (5mm) LED displays 3208 from Sure:
http://www.ebay.ca/sch/i.html?_nkw=3208+display+5mm&_sacat=0&_dmpt=PDA_Accessories&_odkw=3208+display&_osacat=0&_trksid=p3286.c0.m270.l1313
You should be able to fit 10 characters on 64 columns.
As I said earlier, it would also allow to display all kinds of personalized messages.
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