The Arduino site mentioned above is a good start
to learn this environment — which is Java based
and runs on any platform that has Java installed.
There is even a little interface driver/program
named serproxy that comes with the install on
the Mac OS X operating system to simplify the
interface to another computer program to talk to
the Arduino board over a serial port. For more
information on the Processing language and
Wiring language, see the links http://processing
.org/ and
http://wiring.org.co/. I’m going to
be looking into these resources in the future!
Figure 1. SONAR circuit 1.
just looking for learning embedded programming this is a
VERY painless way to learn. Arduino boards (or other
independent offshoots) are fairly cheap and capable, so the
introductory price is also low. Because Arduino is open
sourced, you aren’t locked into anyone’s boards at all. Part
of the Wiring environment’s IDE includes the ability to turn
any ATMEGA8 or ATMEGA168 into an Arduino target; as
long as you have a programmer and downloader software
that can directly program the ATMEGA part. After you
have the bootloader installed, all you need is a serial port
connection (Bluetooth, ZigBee, or any other wireless
connection will work, as well!) and you’re off and running.
Q. I have inherited a pile of parts. Among
these are five pairs of ultrasonic sensors.
At least, that is what I think they are.
One is marked on the back with a 40R and the
other with a T. I am assuming these are transmitters
(T) and receivers (R). There was a slip of paper
in the container with 40TR12B written on it.
I notice that ultrasonics are usually purchased
on circuit boards. Can you help me with a circuit design and
some software tips for making these work? Thanks.
— Anonymous
A. The ultrasonic transducers that you have are from
Jameco, part number 139492. They are 40 kHz transducers which means that they resonate at 40 kHz,
and require a 40 kHz signal to make them work. There are
many, MANY sites on the Internet that detail various folks’
circuits to drive these devices. Here are a couple that I like.
The one shown in Figure 1 is located at www.e-arsenal.
net/robotics/ sonar.html and seems a custom fit to your
transducers. It uses a
MAX232 serial port
driver to deliver a higher
voltage to the transducer
to increase the power
of the output signal
and a common op-amp
to sense the returning
echo. This circuit,
however, requires that
you send a 40 kHz
signal to the circuit;
typically you would use
a PWM output to do
this and wait for a
return echo on the pong
line. This circuit details
using a PIC16F628 to
handle all of the SONAR
details and uses a
similar but simpler
circuit to send and
receive SONAR signals
(see Figure 2). This
Figure 2. A PIC controlled SONAR circuit. Used with permission by GenerExe IT.
14 SERVO 10.2008
