by Michael Chan
Wave This Wand to
Get Your Point Across
Iam sure that everyone has the experience of being
surprised by an unexpected message on occasion. It
could be a declaration of love on a giant stadium
screen, a greeting left behind by a plane, or a commercial
sign beside the highway. Wouldn't it be nice to be able to
deliver a personal message to impress your friends when
they least expect it? Here is a simple gadget that enables
you to wave your personal messages in glow-in-the-dark
words, pictures, or both.
This Messenger project not only lets you surprise your
friends with built-in light displays, but also provides you
with an option of creating your own messages. The device
is compact, portable, and electronically hi-tech! It is a toy
that will appeal to people of all ages. It could be used for
kids at home, fans at concerts, anyone in need of attention
at night, outdoor celebrations, and even creative or
educational purposes for students in school.
manner. Owing to the physical movement of the LEDs
column in waving the Messenger, the changing pattern of
the LEDs is displayed laterally. By matching the rate of
changes of the LED’s pattern, the intensity of the emitting
light, and the swinging speed, static messages can be
perceived and retained in our vision.
The microprocessor — which is dedicated to making
various logical decisions — is the soul of the project. Not
only does it reduce the controlling circuit into a compact
size with a mere handful of electronic components, but it
also enables the device to perform multiple tasks. In total,
the Messenger offers eight operating modes:
The Messenger is a hand-held device which can
display various LED messages when it is waved in the air.
The working principle of the Messenger relies on the
virtual retention of visual images of moving bright objects
on the human retina. The common, flat panel LED displays we see in subway stations or on freeway signs show
messages in a two-dimensional array of LEDs (columns
and rows). To ease the controlling mechanism and reduce
power consumption, columns of LEDs in
such arrays are not on simultaneously.
Instead, only one column of LEDs is
triggered on at a time, while the control is
cycled along the columns. Strictly speaking, the LEDs are dynamically flashing in
sequence. However, the emitting intensity
of the LEDs and the high refreshing rate
of control render a practically stationary
image to our human eyes.
Our Messenger adopts the same
working principle, except that it provides
only one single column of eight LEDs.
The lights are controlled by a microprocessor to flash in a predetermined
Mode 1: Shows all LEDs on.
Mode 2: Shows all LEDs flashing.
Mode 3: Shows single LED running up and down the column.
Mode 4: Shows “2004.”
Mode 5: Shows “I ♥ U.”
Mode 6: Shows “HELP.”
Mode 7: Shows personalized initials.
Mode 8: Sets programming mode for creating own pattern.
An example of a created pattern for my prototype —
which spells, “Bless you,” in Chinese — is shown in Figure 1.
I am not going to explain how to program a microcontroller, as it requires a full article on its
own. I have, however, included a logical
flowchart (Figure 5) for the Messenger
controlling processor as a reference
for those who are ambitious enough
and would like to program their own
processing units. (A HEX image of the
PIC code is available for download from
the Nuts & Volts website at www.nuts
volts.com) There are too many microprocessors available on the market for
me to exhaust them all. Therefore, I will
include some simple, generic routines in
assembly language to illustrate the basics
and leave the fine-tuning to my readers.