Making LED bulb display for displaying characters n scrolling them

achala

Hi All,

I am new to this technology, i want to make a display consisting of LED bulbs to display characters and want to scroll them in fixed intervals. Any suggestions??

kwinn

How many characters on the display?

A propeller is a pretty good choice as the controller for this although a lot of other micros could also be used.

youngbill

See my posting in Basic Stamps,,,under running 64 leds with a max 7219...I have got a lot of help with the links. PS By the way,leds are not called bulbs.

http://forums.parallax.com/showthread.php?t=127046

achala

many thanx!! i read the stuff posted by you, my actual project is to make the advertisement display board containing only single line text. And i need to scroll them also, which components i need to do this? what are the requirements that i need to consider for making it? The board size will be 20"ft * 5"ft. So it should be with good visibility atleast it should be visible from 50"fts distance. How many rows matrix i should have to make?

Gadgetman

Eh...

You don't do anything small, I see...

Boards at that size isn't meant to be viewed at 'short distances'.
(50' is short distance for these)
First you mention ONE row, then ask how many you can fit?
That really depends on the size of the LEDs and the distance it'll be viewed from.
If you stick with one row og 8x8 LED character fields, (and a 7219 for each character) you should end up with something that should be easy enough to scroll.
In fact, I suggest that you start out with a 'small' setup of just a few 8x8 matrixes made up of 3mm LEDs(or 5mm if they're cheaper), then scale up to large LEDs when you know that your design works.

One tip is that the 7219 is serial and can be chained, so it's easy to build a modular design with this chip.

tonyp12

You should use LED Driver IC's as they provide constant current.
http://www.onsemi.com/pub_link/Collateral/CAT4016-D.PDF $1.50 each

BIG LED billboards are not cheep,
if you are using 16 x 64 = 1024 units = $1000 for bright LEDs

Plus probably another $1000 for IC's and supporting commponents.

electrosys

The easiest and the cheapest way is to try some of these LED display boards from Sureelectronic at eBay, like this one:
24X16 Dot Matrix display board, which up to 4 boards can be connected in series, resulting in a 40X10 centimeter display board,
and also this one: 8x32 LED they are easy to interface with a microcontroller to display characters and or whatever you want to.
The prices is about 12$ to 15$ (free shipping) which is a reasonable price to start your project with.

kwinn

achala, the first two items to decide would be:

1 - how high do the characters need to be to be seen at 50 feet. From a distance of 50 feet characters can be quite a bit less than 5 feet high to be legible.

2 - what dot resolution do you want for the characters. This determines the number of dots per column in the matrix. A 7 dots per column matrix is the smallest practical size to display all the alpha characters but letters with descenders (g, j, p, etc) do not look good. A 12 dot per column matrix looks much better.

If you used a 12 dot per column for your 5' x 20' sign each dot would have to be 5"x5", and you would have a total of 48 columns. That would be about enough for 6-8 characters on the display.

achala

Hi,

The design will be:

1)There are words consisting 30 characters in first row in display which will
not scroll.
2)There are words consisting 150 characters(we should have to scroll it).
3)The advertisement board will be situated at 10feet high from ground level.
4)The exact measurement of board will be 20feet wide and 5feet in height.
5)The characters on the display should be visible from 50feet distance. So,
anybody can read it easily.

Please let me know what will be hardware and software requirements to build all this? and where can i get it? and what will be the better choice?

And if first, I have to build a small model of it on small scale how should I start?

LoopyByteloose

Is it outdoor or indoor? I wouldn't bother with trying to DIY an outdoor LED billboard. We have them all over Taiwan and I constantly see them being serviced by technicians after severe rainstorms. The arrangement is tile modules that have to be swapped out and bench repaired. And of course, several intelligent manufacturers have resolved this.

Regarding scrolling or not scrolling sections, it really may not matter as the whole board will likely be multiplexed and fed the graphic data from a server of some sort. Fields that are scrolled are just part of how the data is fed to the display at this point. But you could save a bit of money by providing letters created in LEDs on the fixed portion if that portion will absolutely never change.

kwinn

There are a few questions that must be answered before you can start to design this display.

1 – Will it be used inside or outside?

An outside display needs to be much brighter as well as weather proof.

2 – Does the 30 character count for the first row include spaces between words, and will the characters be fixed or variable width?

The number of columns required is determined by the number of characters (including spaces) and whether or not the characters are fixed or variable width.

3 – What resolution do you want for the characters?

A 5x7 matrix uses fewer leds, but the characters are harder to read and do not look good. Higher resolution such as 7x12 or 9x16 make for better looking characters, but at higher cost, complexity, and power requirement.

4 – Should the 30 character line be the full width (20 ft) of the display (possibly with a small border).

Using fixed width 5x7 characters you would need a total of 180 columns of leds for a line of text, and each pixel would be 1.33 inches square. Using fixed width 7x12 requires 240 columns and 1 inch pixels.