to explain to children why Morse code consists of dots and
Well, morse code, who doesn't know those mysterious sounds that started
the era of global communication. Uhmm... kids. Kids don't know these
sounds and why does this code consists of dots and dashes?
Perhaps they might see this in a movie perhaps but never in
real life. Sure radio amateurs use it still, but I'm no radio amateur
so my kids are not familiar with Morse code. But when we went to the
a museum dedicated to everything regarding aviation) the kids
were introduced to these little rythms that describes letters.
A kind man behind a desk filled with radio equipment, demonstrated how
it all worked and gave us a little piece of paper describing the Morse
code alphabet. And also a few pieces of paper with a
Morse code message, with the instructions to decode these
messages on the ride home. Well the messages got decoded, not
in the car but at home and the kids had so much fun with it, that I
decided to build a little morse code trainer for them to play with. The
idea behind it was to visualize the dots and dashes and
Normally I would take out the microcontrollers and build a device that
would do far much more then required, costing me days or weeks of
tinkering. And because I'm always a little bit anoyed by the complexity
of some projects on the internet that seemingly are impossible to
build an arduino while the only thing the project seems to do
is drive an LED and a speaker. No this project is low
tech, no microcontrollers only a simple regulator and a 555 timer
circuit. I also added a little time constraint to prevent me
from making this project bigger then it should be, a project for a day,
A small video to demonstrate the device, the simplicity, the noises and
lights make it fun for children to use.
The beeper: a simple 555-circuit to generate the beep, simply because I
didn't have a beeper available that sounded the way I liked.
The output is connected to a speaker via a 10uF capacitor, the
resistors are 4.7K, the capacitor is 100nF, this gives approx a 1KHz
The key I had already lying in a box of memories from the past. I
played with it when I was a kid (and it wasn't new when I got it from
my dad), so I decided that this little old key
should be used. It was designed to play with so it shouldn't be in a
box, it should be played with and that is exactly what will happen with
it when this project is done.
For the real morse experience, I figured that the
dots and dashes should be visible. But I did not want to waste rolls of
paper. and honestly using paper would result in all sorts of problems.
If it doesn't runs out, it will get stuck and the pensil that does the
writing will make it complicated if it has to be child proof. Not that
my kids brake anything, I simply want it to last forever. Not using
paper then what else can I use, an electronic display, no! But I
I had some unused glow-in-the-dark tape from a different project. When
stuck onto a rotating cylinder,
it would simulate an endless screen. The pen that writes would simply
be a beam
of light from a white LED (now technically UV is much better for
lighting phosphorescent surfaces, but I did not have a UV LED and I did
not like the idea of exposed UV in toys).
With the help of 80mm PVC pipe and 2 end caps. I drilled a hole exactly
in the middle of the endcaps. One endcap is used for
the connection the the servo motor, the other is used to mount
a small ball bearing for stabillity. The endcaps are drilled very
precisely to prevent wobbling, this was in fact the most important part
of the entire project.
To allow the drum to be safe and durable, the system uses a friction
coupling to the motor. Now this sound very complicated, but in fact it
isn't. The drum is glued to the endcap with the ball bearing but not to
the endcap connected to the motor. So the friction between the endcap
and the PVC pipe is the only connection between the motor and the drum.
Why, well, easy access during assembly and if there is any wobbling it
will not result in forces on the motor. But most inportantly, if
somebody decides to stop the drum by hand or move the drum while the
system is powered of then the drum can turn freely without damaged to
the motor/gears. This method of coupling prevents the motor
from being used as a generator, feeding the circuit
accidentally. Which otherwise could result in damage to the 555 or the
voltage regulator if the motor is turned in the wrong direction. Now
the drum is complete, it can be covered with the glow-in-the-dark tape
to create the display for the dots and dashes.
To drive the drum just a small and slow
motor is required, a servo motor, without the electronics, is perfectly
suited for the job. But in order to use a servo, the endstop must be
removed. Also the electronics are removed as the motor is always on. To
slow down the speed of the drum , the servo motor is driven by 2.5V
from a LM317 regulator, because otherwise when directly connected to 5
volt, it would simply rotate too fast.
The power supply,
well, in 2014 every modern device seems to have a USB connector and a
wall wart to go with it. So instead of searching for a spare power
supply I decided to use such a USB power supply. Now a little spray of
black paint to hide the color of MDF to make it more apealing and I'm
done. The end result is shown below.Here you see the paper containing
the morse code alphabet and the "mysterious message" the kids decoded.
I was suprised how quickly they did this and the joy it gave them. The
device below visualizes the dots and dashes of the sounds making it
easier to see what the've done and creating the illusion of the