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This is only a preview of the June 1989 issue of Silicon Chip. You can view 44 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Articles in this series:
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Part 4
Build your own
LED Message Board
In this final article, we show you how to
build and test the display panel. We also
tell you how to use the system and list the
control commands that provide all the
special effects.
Design by DON McKENZIE
As noted in previous articles, the
display is made up of four printed
boards, each accommodating 24
columns of LEDs (168 in all). To
simplify the description, we will
assume that you are going the
whole hog and building a 4-board
display. The procedure for building
each display board (DIS5MM) is the
same.
Before installing any components
70
SILICON CHIP
on the display board, carefully
check it out on both sides for shorts
or open circuit tracks. Use your
multimeter to check that the ground
and + 5V lines are not shorted
together.
It is very important to follow the
correct order of assembly for the
display panel. If you install components in the wrong order you will
•find that others cannot be fitted.
Supplied in the short form kit for
the LED Message Board is a LED
alignment tool. As its name implies,
this is for aligning the LEDS so that
they are all evenly positioned to
give the professional finish that a
good message board deserves.
There are four holes on the
perimeter of the LAD (LED alignment device) which are sized so
that ½ -inch long Va-inch BSW
screws can be self-tapped into
them. These locate the alignment
tool over the DIS5MM circuit
board.
Spray job
The DIS5MM printed circuit
board has to be sprayed black
before soldering anything to it.
Tape the bottom 20mm of the circuit board, where the ICs are, with
a piece of masking tape and lightly
spray the board with quick drying
matte black paint. This is done so
that reflections from the LEDs will
not degrade the display.
Spraying may have to be done
several times. Several light, even
coats are better than one heavy
coat which will clog up the solder
holes.
It is most important that all LEDs
are the same type number so that
there are no inconsistencies in colour or brightness between each
LED. It is also very important that
the LEDs have an intensity
somewhere between 7-10 mcd
(millicandela) and a viewing angle
of 36 degrees or greater. Most red
LEDs that you would buy off the
shelf would be 0.8 mcd which is
totally unsuitable for the job
whereas most green or orange
types are 8.7 mcd (the range is very
broad, starting at about 0.8 mcd
and going to 350 mcd, or even
higher).
Do not buy high intensity LEDs as
they have a typical viewing angle of
only 15 degrees which is unsuitable. If your store owner cannot
tell you the intensity and viewing
angle of the LEDs then don't buy
them as it is a murderous job to
desolder all those LEDs once they
are in the PCB. Typical examples of
suitable LEDs are the Liton brand
LTL-4223 (red), LTL-4233 (green)
and LTL-4293 (orange) which all
have an intensity of 8. 7 mcd and a
viewing angle of 36 degrees.
One last point: buy all your LEDs
at once, even if at first you are go-
One of the 7 x 24 LED panels. The header socket is on the copper side of the
board. Note that the component side of each LED board is painted black to
provide enhanced contrast and prevent reflections.
ing to build just one panel. as you
may not be able to get the same type
again at a later date.
Now comes the fun part! Starting
from the left hand side of the panel
insert a 7 x 7 matrix of LEDs with
their ea thodes towards the bottom
of the board (ie, towards the ICs).
You may find that some brands of
LEDs have large tangs on their legs
which wont pass through the holes
in the PCB. Don't worry - providing they are all the same height,
it does not matter whether the LEDs
are sitting flush with the circuit
board or are slightly raised.
Carefully position the LED alignment tool over the matrix of LEDs
and lightly finger tighten some nuts
onto the screws protruding on the
underside of the display board to
hold the tool in place.
The panel can now be turned
over without fear of dropping any
LEDs or disturbing their position
while they are soldered in place.
After doing two lots of 7 x 7 LEDs,
start on the righthand side of the
board and that should leave just a 3
x 7 matrix in the middle to finish off
the panel.
The 2 x 26-pin dual row male
header pins may now be soldered in
but be careful as they are inserted
from the solder side of the circuit
board. This is because connections
to and from the panel are made via
headers and cables from the back
of the board. Note that Jl and JZ are
the only components mounted on
the solder side of the board.
The 24 330 ½ -watt resistors can
Fig.I: a LED alignment
tool (supplied with the
short form kit) is used to
accurately position the
LEDs on the PC board.
The two header sockets
must be installed on the
copper side of the board
before the 33rl resistors
are installed.
J2 OUTPUT
ON OTHER SIDE OF BOARD
JI INPUT
ON OTHER SIDE OF BOARD
JUNE 1989
71
PARTS LIST FOR
LED DISPLAY PANEL
1 PC board designated
DIS5MM (available from Don
McKenzie
1 perspex channel (available
from Don McKenzie)
1 baseboard, 29 x 3.5 x
0.75-inch
2 26-way dual-row male header
strips
7 1 4-pin IC sockets
1 68 5mm LEDs, all same
colour and intensity
Integrated circuits
E1 ,E3,E5,E7 - 75492 hex
inverting buffer
E2,E4,E6 - 7 4LS164 serial
in/parallel out shift register
The four LED panels are "daisy-chained" together via the Jt and J2 header
sockets on the copper side of the boards.
Passive components
BC1-BC6 - .01 µF ceramic
capacitors
R1-R24 - 330 ½W resistors
Note: multiply all parts by 4 for
the full 4-panel (16-character
display).
The Jt header on the rightmost panel is connected to the control unit via a
25-way cable terminated with a header socket and DB-25 connector.
now be installed but take care to
provide clearance when installing
the resistors that go over the solder
pins of Jl and J2.
Install the 6 .OlµF ceramic
bypass capacitors and the 7 sockets
for the ICs, taking note of the orientation of pin 1 in each case. Now install the ICs into their respective
sockets and that completes one
display panel. If you are building
more than one panel it will
necessary to repeat the above
procedure.
With the panels completed, you
72
SILICON CHIP
can link them together via short
26-way header cables by way of the
Jl and J2 header pins. Note that
when the panels are butted up next
to each other with the ICs towards
the bottom, the main connection
from the controller will connect
with Jl on the righthand side panel
and will then be daisy-chained
through the other panels.
You can now apply the power
and you should see the default ROM
based test message cycling thr,ough
on the display panel. Adjust the
50k0 trimpot on the interface board
till you get the most stable display
in both static and moving display
modes.
The recommended method of
housing four panels is as follows:
Cut a sheet of 19mm particle
board as shown in the diagram and
drill 16 1/s-inch holes so that the
display panels can be mounted on
25mm spacers. Cut a small section
away so that access can be gained
to Jl on the righthand panel.
If you can accurately cut this
board to the dimensions shown it
should fit snugly into the grey tinted
acrylic housing which is available
from the designer, Don McKenzie.
Operator Instructions
The moving message board will
accept a message that can-be either
a straight ASCII message or it can
have some control codes (entered
with the Ctrl key) embedded into the
message string. These control codes
will enable various attributes to be
added to the message. A complete
list of these attributes is included
below.
As noted previously, there are
two ways of entering a message into the moving message board. The
The LED display panel is covered by a grey Perspex channel which is suitable for all LED colours. A ready-made
channel can be ordered from the designer, Don McKenzie, for $50 plus $15 p&p (see panel).
0.75" THICK PARTICLE BOARD
16x1/B" HOLES
0.4"
6.6"
6.6"
CUT OUT TO
SUIT CABLE
6.6"
6.6"
0.6"
118" ACRYLIC SHEET
CUT TWO END CAPS TO SUIT
AND GLUE AT EACH ENO
Fig.2: here are the dimensions for the baseboard and the perspex channel for the display board. Note that all
dimensions are shown in inches.
first way is to hook up a personal
computer which has a Centronics
parallel printer output to the
female Centronics plug on the back
of the controller. Be sure to switch
the front panei toggle to the computer position. Data can then be
loaded into the message board by
sending the data down the printer
port.
An easy way to do this is to use a
wordprocessor or similar text
editor which produces ASCII text
(Wordstar is not suitable). Type
your message and then embed the
JU N E 1989
73
control characters depending on
the way you wish your message to
be displayed on the moving message
board. Then just print the file as if
it was going to a printer and you
should see your message appear on
the display.
The other method is to connect
an IBM PC XT or compatible type
keyboard to the 5-pin DIN plug on
the back of the controller. When using the keyboard method, you enter
the EDIT mode by pressing HOME.
This gives a static display of the
first 16 characters of the current
message starting at the left column
and any control characters that are
embedded in the message will be
shown as flashing characters.
The message board software supports 11 message buffers that will
enable you to store up to 10
messages of your own plus the
default ROM-based test message.
You can select which message
buffer you wish to be active by
pressing one of the function keys.
Fl gives you buffer 1, F2 gives buffer 2 and so on.
You should see a flashing full
block on the 1st character in the
message. This is the display cursor.
This can be moved back and forth
by the keyboard cursor keys. You
need to go into Insert mode for
editing.
The Up or Down cursor keys will
jump forward to the next screen or
to the prior screen, while the Home
and End cursor keys will jump to
the Start or Finish of the message
and the cursor will be flashing on
the 1st character on the lefthand
side of the display. By using these
keys you will be able to quickly
move about the message string to do
editing.
The initial edit mode is the Overwrite mode which will accept any
characters typed on the keyboard
and overwrite them onto the existing message. This mode is indicated by a full block cursor.
If the INS key is pressed to go into
the edit mode, this is indicated by a
flashing half-block cursor. The INS
key will toggle between these edit
modes and the DEL key will Delete
the character shown under the current cursor irrespective of whether
you are in the Insert or Overwrite
mode.
74
SILICON CHIP
Keyboard Commands
Home: keyboard attention; stops the current display and enters Edit
mode on the current buffer at the first character.
ESC: run current buffer. After you are happy with your editing this will
display the current message.
F1·F10: selects the specified buffer tor editing.
Ctrl 0: displays the ROM test message buffer. Note that this cannot be
edited.
Ctrl 1 to Ctrl 4: selects the number of panels that you wish to use from
1 to a maximum of 4 panels. (Note: the power up default is 4 panels).
Ctrl 8: tests the type of IBM keyboard that is connected and displays
this in buffer 1 0 (there are 3 types supported).
Ctrl 9: copies the ROM test message into buffer 1 .
Ctrl F1 to Ctrl F10: erases the specified buffer .
DEL: deletes the character under the cursor.
INS: toggles the insert mode on and off.
END: jumps to the end of the current buffer.
UP-arrow: moves to the next page.
ON-arrow: moves to the previous page.
RT-arrow: moves cursor right one position.
LT-arrow: moves cursor left one position.
Note: buffers 1 and 2 are each 2K bytes long and are also used to capture
the input from the Centronics input and juggle appends etc. Therefore,
anything in this buffer will be lost when sending a string via the computer.
Buffers 3 to 1 0 are each 256 bytes long.
Control Commands
Ctrl A: this will append the new message to the old.
Ctrl C: this clears the board and erases the current message from memory.
Ctrl D: this will load the new message immediately; ie, will not finish current
message.
Ctrl Ex: this will enable the 'screen dump' filter to be changed. See note 1.
Note: the above commands only apply to the Centronics input and are not
applicable to keyboard input.
Ctrl F: this will toggle the Flash mode ON and OFF.
Ctrl Gx: this will pause and Flash the display tor "x" seconds. See notes 2
& 3.
Ctrl I: this is the Tab character which is displayed as 4 spaces.
When you are finished editing
your message just press the ESC key
and your message should start to
move onto the display board.
The absence of any Control
character will display the new
message after the last has finished
its cycle. A list of the Control (Ctrl]
commands that can be embedded
into the text string is shown in
the accompanying table.
Note that each line to be
displayed must have a full 16
characters of text when control
characters are embedded, otherwise the display will not work correctly. If necessary, the line can be
padded with spaces to make up the
necessary 16 characters.
Finally, note that some commands must be embedded as leading attributes while others are
embedded as trailing attributes.
These are listed in the table.
~
Ctrl J: this is the LF (linefeed) character which is ignored by the moving
message display.
Ctrl L: this is the FF (formfeed) character. See note 1 .
Ctrl M: this is the CR (carriage return) character. See note 1.
Ctrl N: this will show the next message as a static display after the old
message is finished.
Ctrl 0: this command will shoot the message one character at a time onto
the screen from the right (shot on).
Ctrl Px: this command will pause the display for x seconds. See notes 2 &
3.
Ctrl Q: this command will clear the board by moving the display across to
the right (exit stage right).
Ctrl R: this command will toggle the display between large (twice normal
size) and normal characters.
Ctrl T: this command will display the next screen by scrolling the text down
and over-writing the old screen (wipe down).
Ctrl U: this command will display the next screen by scrolling the text up
and over-writing the old screen (wipe up).
Ctrl V: this will display the next screen by scrolling the text down, pushing
the old screen as it goes (roll down).
Ctrl W: this will display the next screen by scrolling the text up, pushing the
old screen as it goes (roll up).
Ctrl X: this will display the next screen by wiping over the old screen to the
left (wipe back).
Ctrl Y: this command will display the next screen by wiping over the old
screen to the right (wipe forward).
Ctrl Z: this is the EOF (end of file) marker and is the normal message terminator and cannot be created or overwritten while in Edit mode.
Note 1 : with the Ctrl E command to enable the screen dump filter, certain
characters will be translated as follows:
(a) with Ctrl E0, CR and FF are ignored; spaces are as ordered.
(b) with Ctrl E1, CR is translated into a Tab , FF is translated into a Tab;
spaces are limited to a maximum of four spaces .
Note 2: some commands require a numerical parameter to be included for a
time delay in seconds: 0 = ½ second delay; 1 = 1 second, 2 = 2
seconds, up 9 seconds delay.
Note 3: As the Ctrl Gx and Ctrl P commands are applicable to the entire
screen they are 'trailing attributes'; ie, the message is sent first then the attribute is sent.
Note 4: Ctrl T, U, V, W, X and Ctrl Y are 'leading attributes' which affect the
whole screen. Note that each line to be displayed must be padded with
spaces to a full 16 characters for the line to be displayed correctly.
IX-A-KIT
Kit Repairs -
$15 per hour.
Normal Rate -
$30 per hour.
No charge for kits that can't be
repaired.
3 month Warranty on repairs .
Construction -
fixed or hourly
1 2 Month Warranty on
Manufactured Kits.
Custom Designing ,
Manufacturing, Large or Small
Quantitites .
YCAL
ENTS
Design, Manufacture, Repair of
Electronic Equipment.
(02) 633 5897
Unit 4,
62 Great Western Highway,
Parramatta, NSW 2150.
Trading hours:
8am to 3pm Monday to Friday.
D.DAUNER
ELECTRONIC
NTS
WE STOCK A WIDE RANGE
OF ELECTRONIC PARTS
•
*
for
Development • Repair
• Radio Amateur
• Industrial Electronic
• Analog and Digital
WHILE STOCKS LAST
THE FAMOUS TR-DIP METER
(as featured May '89) $98.00
* CRO-VALVE 3ACP2A $45.00
* PHILIPS IR-IMAGE CONVERTER
Where to buy the parts
A complete set of printed circuit boards plus the programmed 2764
EPROM and full instructions are available from the designer, Don
McKenzie , for $150. The specially made grey Perspex channel, suitable for all LED colours , is also available from Don McKenzie for $50
plus $1 5 for packing and postage. Write to Don McKenzie, 29 Ellesmere Crescent, Tullamarine, Victoria 3043 .
All the semiconductors and other parts are readily available from
parts suppliers such as Jaycar Electronics, Dick Smith Electronics, Altronics , Geoff Wood Electronics and David Reid Electronics.
VALVE XX1080 $45.00
(For use in infrared sight experiment systems)
Come and see.
Showroom:
51 Georges Crescent,
Georges Hall, NSW 2198
(Behind Caltex Service Station In Birdwood Road)
one 724 6982
TRADING HOURS:
Monday to Friday 9.00 a.m. to 4.00 p.m.
Saturday from 9.00 a.m. to 12.00 noon.
JUN E 1989
75
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