PS_2_You-LED-Sign.pdf

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PS/2/You LED Sign
PS/2/You LED Sign
Written By: Immanuel McKenty
TOOLS:
Chisel (1)
Computer with internet connection and
USB port (1)
Desoldering braid or solder sucker (1)
Drill and bits: 5/64", countersink (1)
File (1)
Glue gun and hot glue (1)
Hammer or mallet (1)
Handsaw or chop saw (1)
Measuring tape or long ruler (1)
Multimeter (1)
Needlenose pliers (1)
(optional) handy for plugging in
breadboard jumpers
Screwdriver, medium (1)
Soldering iron and solder (1)
Table saw (1)
(optional)
Wire cutters (1)
PARTS:
Make PS/2/You Kit (1)
from the Maker Shed
(makershed.com/ps2you). Our kit
includes almost everything you need to
build your own PS/2/You sign except for
the enclosure.
Dot matrix LED display modules, 8×32,
with ribbon cable (3)
Sure Electronics item #DE-DP106, about
$9, or equivalent module. This item was
recently discontinued but is available on
eBay.
Computer keyboard with PS/2
connection (1)
They're readily available at thrift stores.
You can also use a USB keyboard with a
USB-to-PS/2 adapter.
Ardweeny microcontroller (1)
This small, cheap Arduino clone fits into
a standard 14-pin DIP socket, but it
doesn't come with an onboard 5V voltage
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PS/2/You LED Sign
Wire cutters (1)
regulator or an FTDI USB-serial
converter for programming.
5V voltage regulator (1)
You can use a 7805, but the low-dropout
LM2937 will make your batteries last
longer, especially with lower-voltage
NiMH AAs.
PS/2 port (1)
from an old PC motherboard; ask your
local computer shop.
Breadboard (1)
Breadboard jumper wires, or solid core
22AWG wire (20)
(around 20, multiple colors) Jumpers are
easier to use and well worth the
expense.
FTDI serial programmer (1)
such as the FTDI Friend, Maker Shed
#MKAD22, $15
AC wall adapter (1)
can be found for $1–$2 at most thrift
stores
DC power jack (1)
which ever matches your adapter
Power switch (1)
(on-off-on)
Capacitor (1)
Batteries (6)
Battery holder (1)
Battery holder (1)
in a long, flat 2x2 configuration
Wire (1)
4' total
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PS/2/You LED Sign
Electrical tape or heat shrink tubing (1)
Acrylic/plegixglass sheet (1)
Lexan will work great but is more
expensive
Wood screws (8)
1 1/4" long
Wood screws (6)
1/2" long
Wood screws (12)
1/2" long (optional)
Dimensional lumber (1)
(3/4" x 3 1/2"), 4' length, or 1 x 2 (3/4" x
1 3/4") , 8' length
SUMMARY
It all started with a small LCD salvaged from an old printer. I recruited my code-savvy older
brother, Adam, and we soon had the LCD displaying text from an Arduino microcontroller.
This was neat, but it was inconvenient having to plug the Arduino into a computer for
reprogramming whenever we wanted to change the text.
We needed something for inputting the text, and it didn’t take long to find a PS/2 keyboard
code library for Arduino — which confirmed my observation that anything that communicates
with wires has probably been hooked up to an Arduino. I salvaged a PS/2 port from an old
computer motherboard, and after some trial and error, we could plug in a common PS/2
keyboard ($5 new) and type messages directly into the Arduino and out to the LCD.
The LCD was so small, however, that hardly anyone noticed our witty remarks. We needed a
bigger display. After looking at many appallingly priced commercial LED matrix products, we
found a new and much cheaper offering:
Sure Electronics’ 8×32 display boards. They cost $9 each and you can cascade up to four
into one long display. We ordered three, and by the time they’d arrived, the Arduino
community had already produced a library to run them. (Our code is based on two open
source Arduino libraries: PS2Keyboard, by Christian Weichel; and MatrixDisplay, by Miles
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PS/2/You LED Sign
Burton.) The result is our PS/2/You system, which displays keyboard-typed messages in 2"-
tall LED letters that can be read from quite a distance. You can store and switch between six
different lines of text, and it automatically scrolls through lines that are too long for the
display. Power comes from an AC adapter or six AA batteries for portable operation, and the
whole thing is housed in a sturdy wooden frame.
Step 1 — Build the frame.
Cut the 1×4 lumber in half lengthwise to make 2 strips about ¾"×1¾" (a nominal 1×4 is
actually around ¾"×3�½"). Use a narrow-kerf blade if possible.
Line up the 2 boards beside each other on a flat surface with their narrow edges up. Place
one of the display panels facedown between the boards, so that the flanges on the panel
rest on the boards, with the protruding LED matrix between them. Gently squeeze the
boards snug against the sides of the LED matrix, and measure between the outside edges
of the boards. This measurement is the length of the frame’s end pieces. (Remember this
measurement for the following steps.)
Use a chop saw or handsaw to cut a 45° angle on one end of each piece, oriented so the
cut goes diagonally across the narrow edge. Measure 18¼" down the board’s length from
the inner edge of the cut, and make a second 45° cut that angles back out. Repeat on the
second board. These will be the 2 long sides of the frame.
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PS/2/You LED Sign
Step 2
On each of the leftover board pieces, mark the distance measured measured in Step 1
down from the sharp, outside edge of the miter cut, along the longer face of the board. Cut
one at 45° angled in from the measured length (the mirror image of the first cut), which will
be each piece’s longest dimension. Don’t cut the other piece yet.
Desolder the PS/2 port from its donor motherboard. Line up the DC jack, PS/2 port, and
power switch atop the edge of the marked but uncut short piece of wood. Mark out a notch
in the edge of the board just wide enough for all of them to fit next to each other and deep
enough that the tallest component will sit flush.
With a handsaw (or chop saw) cut the 2 edges of the notch. Make a few cuts to the correct
depth in the middle of the notch, then chisel out the rest of the wood and file the bottom of
the notch smooth. The ports and switch should slide into the notch easily but without extra
space. Cut the second (notched) end piece just like the first mitered end piece.
NOTE:
The frame style isn’t crucial, so let your creativity (and materials) have a
say in the design. I had a woodshop at my disposal, so I made something like an
extra-deep picture frame with mitered corners and a slot cut in the long sides to hold the
display panels.
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