 |
| Block Diagram |
On the right of the diagram is the LED matrix which consists of seven
rows of 64 LEDs. Each of the rows has a switch circuit, which supplies current from
the power supply when activated. These row
switches are controlled by a set of seven latches which receive data from the data bus. An eighth latch is
used to activate the piezoelectric sounder circuit.
The columns also have switch circuits, these being
designed to sink current to ground when activated. The column switches are also
controlled by latches. Arrange in eight groups of eight. Each group can be
written to from the data bus under the control of eight column group select
lines which make up the select bus. Both the data and select busses are buffered
before connection to the column latches.
On the left side is the CPU circuitry.
The clock circuit provides the master timing reference. While the reset circuit
ensures that the CPU starts executing program instructions from the beginning when
power is first applied. The EPROM and RAM are connected to the CPU via common
address and data busses and are selected under the control of the memory
address decoder circuit.
The I/O (lnput/Output) address decoder circuit uses
control signals from the CPU to select the row latches. The column latches and
the keyboard buffer. The keyboard buffer reads both the keypad and the DIL
switches simultaneously. The data bus, select bus and the row latch signals are
connected to the display section via a 20-r.r'ay ribbon cable. While a I/O-way
rib-'on cable is used to connect the keypad to the keyboard buffer.
LED
display signs can be programmed to have changing images or lettering, or animated
graphic displays that keep alternating as different lights come on and off.
Neon signs, while they can be made to show an animated design with different
tubes switching on and off, have less overall versatility. LED display signs
tend to be seen as modern, but often rather clinical and cold. Neon signs are
perceived as warmer and more inviting, with a retro feel that often suits small
businesses attracting individuals.
The smallest
unit of the LED display screen that can be controlled and can be turned off or
on at various brightness levels. The full name of pixel is “picture element”.
In a 3 colour LED display, the pixel is made of 3 different colours – red,
green and blue. Each part is made up by one LED or several LED’s, in theory
that the different 3 colours can display every colour by adjusting the led
brightness. Therefore, pixels are points of light that illuminate
together to form letters, words, graphics, animation and video images.
