Hardware Reference
In-Depth Information
Ultrasonic Distance Ranger Example
The MaxBotix (
www.maxbotix.com
) ultra-
sonic sensors measure distance using
a similar method to the Sharp sensors,
but theirs have a greater sensing range.
Instead of infrared, they send out an ultra-
sonic signal and wait for the echo. Then
they measure the distance based on the
time required for the echo to return. These
sensors require 5V power (the LV series
can operate on 2.5-5V), and return their
results via analog, pulse width, or asyn-
chronous serial interface. They're available
from MaxBotix, Spark Fun, Adafruit,
Pololu, and many of the other retailers
listed in this topic.
MATERIALS
» 1 Arduino module
» 1 Maxbotix LV-EZ1 ultrasonic ranger
» 3 male header pins or 3 jumper wires
Distance rangers are great for measuring linear distance,
but they have a limited conical field of sensitivity, so
they're not great for determining location over a large
two-dimensional area. The MaxBotix LV-EZ1 sensor, for
example, has a cone-shaped field of sensitivity that's
about 80-degrees wide (though the sensitivity drops off at
the edges) and 6.4 meters from the sensor to the edge of
the range. In order to use it to cover a room, you'd need to
use several of them and arrange them creatively. Figure
8-3 shows one way to cover a 4m x 4m space using five
of the rangers. In this case, you'd need to make sure that
no two of the sensors were operating at the same instant,
because their signals would interfere with each other. The
sensors would have to be activated one after another in
sequence. Because each one takes up to 5 milliseconds to
return a result, you'd need up to 250 milliseconds to make
a complete scan of the space.
Measuring distance top-to-bottom
Sensor
1
MADE
IN I TALY
DIGITAL
(PWM~)
-
+
L
UNO
ON
TX
RX
ARDUINO
RESET
ICSP
Sensor
3
Sensor
2
POWER
ANALOG
IN
Measuring distance side-to-side
Sensor
4
Sensor
5
