28125 Parallax Inc, 28125 Datasheet - Page 308

• 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

SUMMARY
Frequency sweep was introduced as a way of determining distance using the Boe-Bot’s
IR LED and detector.
37.5 kHz (most sensitive) to 41.5 kHz (least sensitive). The distance was determined by
tracking which frequencies caused the IR detector to report that an object was detected
and which did not. Since not all of the frequencies were separated by the same value, the
LOOKUP
by a
Control systems were introduced along with closed loop control. Proportional control in
a closed-loop system is an algorithm where the error is multiplied by a proportionality
constant to determine the system’s output. The error is the measured system output
subtracted from the set point. For the Boe-Bot, both system output and set point were in
terms of distance. The BASIC stamp was programmed in PBASIC to operate control
loops for the both the left and right servos and distance detectors. By re-sampling
distance and adjusting the servo output before sending pulses to the servos, the control
loop made the Boe-Bot responsive to object motion. The Boe-Bot was able to use
proportional control to lock onto and follow objects, and it also used it to track and
follow a stripe of black electrical tape.
Questions
1. What would the relative sensitivity of the IR detector be if you use
2. Consider the code snippet below. If the
3. In what order are PBASIC math expressions evaluated? How can you override
FOR…NEXT
command was introduced as simple way to use the counting sequence supplied
send a 35 kHz harmonic?
harmonic?
be placed in the
prime
LOOKUP index, [2, 3, 5, 7, 11, 13, 17, 19], prime
that order?
Watch the Boe-Bot in Action at www.parallax.com!
You can see the Boe-Bot solving Chapter 8 Project 2 and other Robotics video clips in the
Robo Video Gallery under the Robotics Menu at www.parallax.com.
store when
loop to index sequential lists of numbers.
FREQOUT
prime
index
was used to send IR signals at frequencies ranging from
variable in this
is 0, 1, 2, and 7?
What is the relative sensitivity with a 36 kHz
index
LOOKUP
variable is 4, which number will
command? What values will
FREQOUT
to