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WHERE THE PAST MEETS
By David Goodsell
Several months ago, I bought a vintage
Allied Radio Knight-Kit 12-in-1
Electronic Lab on eBay. It used a 12K5
low voltage vacuum tube instead of
transistors, as shown in Figure 1.
As I was wiring up my "wireless AM
broadcaster" project, it hit me.
Why not combine the past with the
present? Put an Arduino with a
vacuum tube shield — a Retro-Shield!
Actually, this idea didn’t just come out of the blue. I
had been puttering around with an Arduino Uno from
RadioShack, and since the 12K5 vacuum tube only
needed 12 volts to operate, I made the connection.
In my head, I could see the end result. It would be a
stack of shields with the vacuum tube on the top board,
glowing in the dark. I wasn’t sure yet what it was going to
do, but I knew it would be cool.
30 April 2013
Before I get into the details, I want to say how much
fun this project turned out to be. First, I successfully
dissected a vacuum tube and learned how it worked.
Secondly, I had fun broadcasting silly messages around the
house, along with Christmas music that at the time made
our holiday very special. The talking clock drove my wife
nuts, but I loved it. And finally, I built my first Arduino
shield and managed to get it working just the way I
wanted. What more could I ask for?
An mp3 sample of my broadcasts can be found at the
article link. The first portion of the sample is a sentence
generated by the talking clock; the second section is from
a music player; and the last part is my voice, using a
■ FIGURE 1. The 12-in-1 Knight-Kit
uses point-to-point soldered wires to
build the projects.
microphone. The sequence is repeated twice. I think you’ll
Back to Business
Now, back to the project. How could I possibly wed
the broadcaster to an Arduino? I remembered some ads
for sound-generating shields that produced voices and
weird sounds for robots and talking clocks. A GinSing
Sound Synthesizer shield looked interesting, but the
demos sounded a little too unnatural for me.
The SpikenzieLabs VoiceShield had a different
approach. It simply stored digitized audio, then played it
back when triggered by an Arduino. The VoiceShield’s
memory could hold four minutes of audio. One
application for it was a talking clock. You could load it
with 80 prerecorded words, such as: the, time, is, now,
one, o’clock. Or, you could put in any audio you wanted.
So, at last I had a vision of the final configuration; take
a look at Figure 2. It would be three boards: an Arduino
on the bottom, a VoiceShield in the middle, and the
broadcaster on top. I figured that once it was finished, I
would program the Arduino to announce the exact time —
once every five minutes — to all the radios throughout the
house. I was sure my wife would love it.