28125 Parallax Inc, 28125 Datasheet - Page 284

• Manufacturer Part Number: 28125
• Description: TEXT ROBOTICS
• Manufacturer: Parallax Inc

Specifications of 28125

• Title: Robotics with the Boe-Bot
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Another way to think about it is that the most sensitive frequency will detect the objects
that are the farthest away, while less sensitive frequencies can only be used to detect
closer objects. This makes distance detection simple. Pick 5 frequencies, then test them
from most sensitive to least sensitive. Try at the most sensitive frequency first. If an
object is detected, check and see if the next most sensitive frequency detects it.
Depending on which frequency makes the reflected infrared no longer visible to the IR
detector, you can infer the distance.
Programming Frequency Sweep for Distance Detection
Figure 8-2
In this example, the object is in Zone 3. That means that the object can be detected when
37500 and 38250 Hz is transmitted, but it cannot be detected with 39500, 40500, and
41500 Hz. If you were to move the object into Zone 2, then the object can be detected
when 37500, 38250, and 39500 Hz are transmitted, but not when 40500 and 41500 Hz
are transmitted.
Frequency Sweep is the technique of testing a circuit’s output using a variety of input
frequencies.
shows an example of how the Boe-Bot can test for distance using frequency.
Figure 8-1
Filter Sensitivity
Depends on
Carrier Frequency