# How hard would this be to make?

Discussion in 'Electronic Basics' started by John Comma Smith, Jan 26, 2005.

1. ### John Comma SmithGuest

I got a bit of a weird request for circuit people out there. I want to make
a display out of LEDs. I'm not sure of the size of the display as of yet,
but I want to be able to program the LEDs to blink in a random fashion,
scroll text across them, or a combination of that. How hard of a circuit
would this be to build, and what would be the best chip to program from my

2. ### peterkenGuest

- put the leds in a matrix
- use a microcontroller for the sequence
(needs "calculation" in case of text)
- control them at rather high frequency, so ni flickering occurs

or just buy an existing module... :-D

3. ### John Comma SmithGuest

I was thinking of buying an existing one but do they make them in a 5 x 19
LED size? How would I go about making a matrix for the LEDs and what type of
microcontroller would you suggest? Thanks.

4. ### peterkenGuest

don't know what sizes of display exist, I think many varieties do
try googling for it

using an electric matrix of 8x8 lines gives 64 possible led's
this only uses 2 processor ports directly
OR
decoder
using 2 8-bit latches gives you again a matrix of 64 leds
the controller to be used can be any kind but must have enough ports
- at least 1 if using addressable latches
or
-(number of leds)/64 * 2 ports if controlling directly (=this number is
identical to the number of latches if used)
and enough calculation power to do the job
the needed power of the controller is related to the number of leds to be
connected since they must be calculated to be on or off and to create a
smooth image if moving

principle of the leds: (2x2 lines depicted)

B1 B2
| |
| |
A1 ---+--------+-----
\ | \ |
\| \|
+ +
A2 ---+--------+-----
\ | \ |
\| \|
+ +
| |

all leds are connected as the diagonal lines are drawn
all leds arranged in same polarity (direction)
so 2x2 lines gives you 4 led's to control (and one half port or latch to be
used)

5. ### John Comma SmithGuest

This doesn't seem all that hard to do. Do you know of a website that shows
this in more detail?