Page 195 - 15 Dangerously Mad Projects for the Evil Genius

172 15 Dangerously Mad Projects for the Evil Genius

Figure 13-20 A chart showing ambient light compensation

means that the IR LED is doing its work and Control Software
shining a bright beam into the phototransistor, so
If you have not used Arduino before, then
we are naturally keeping the influence of external
hopefully you will be impressed by the simplicity
light fairly low.
and power of this little microcontroller board. Let’s
The difference line remains fairly flat, which is
have a look at the program that controls the
what we want, and means that external influences
levitation machine. (See Listing 13-1.)
such as turning on a bright light near the levitator
The Arduino boards use the C programming
(between samples 43 and 90) and shading it with a
language. It is beyond the scope of this book to
large box (between samples 118 and 180) were
explain the whole C language, but if you have a
both compensated for.
basic familiarity with programming, you should be
Interestingly, you can see the mains frequency
able to understand the following explanation.
flicker from that first event, where the brightness
The program starts with some variable
of the lamp fluctuated with the mains frequency.
declarations. The lines that start with a // denote
This leaves a small trace on the compensated
comment lines that explain what is happening.
signal, but not enough to worry about.
We then have a “setup” function that says how
the various connections on the board are to be
used, and sets the baud rate for communication
with the Serial Monitor. A message saying what