Parallax 28034 Manuel utilisateur

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Infrared Line Follower Kit (#28034)

The Infrared Line Follower Kit from Parallax provides eight infrared emitter and receiver pairs for high-

precision line-following applications. Mounting hardware for both the Boe-Bot®and Stingray™robots are

also included for easy startup.

All IR frequency generation is done onboard using an ICM7555 chip, requiring no external signaling. This

allows for simple interfacing to the Infrared Line Follower, since the user only needs to read the state of

each IR receiver to detect white or black surfaces. An “Enable” pin is also included which when pulled low

puts the Infrared Line Follower into low-power mode.

Features

Compatible with both the Boe-Bot and Stingray robots from Parallax

Onboard 3 V regulator for easy use with Propeller-powered robots

Easily adjust 38–43 kHz IR frequency using an onboard potentiometer (See Calibration, page 8)

Onboard LEDs for instant line detection communication

High immunity to ambient lighting conditions

Mounting hardware included

No external signaling required

Key Specifications

Power Requirements: 3.3– 5.5 VDC;

maximum 35 mA working, 30 µA

when disabled

Communication: Single bit high/low

output for each IR emitter/receiver

pair

Operating temp: 32 to 140 °F

(0 to 50 °C)

Dimensions: 3.03 x 1.33 in

(7.7 x 3.4 cm)

Application Ideas

Line following

Maze navigation

Robotic contests

Detect line stripe width

Edge detection

Bill of Materials

Part # Quantity Description

- 1 Infrared Line Follower PCB

- 2 10” 4-pin female/female cables

- 1 10” 3-pin female/female cable

- 2 4-pin male/male headers

- 1 3-pin male/male header

710-00007 2 7/8" 4-40 pan-head screws

700-00028 2 1/4" 4-40 pan-head screws

700-00060 2 1" round standoffs

713-00007 2 1/2" round spacers

700-00003 2 4-40 x 3/8" nuts

Additional Items Required

#2 Philips-head screwdriver

Black 3/4" electrical tape

White poster board

Resources and Downloads

Check for the latest version of this document, free software, and example programs from the Infrared

Line Follower Kit product page. Go to www.parallax.com and search 28034.

Theory of Operation

Upon connecting power, the onboard ICM7555 chip begins sending a 38–43 kHz signal through all 8 IR

LEDs. If the IR LED is over a white surface, light is reflected to the IR receiver, and its output is low.

When the IR LED is over a black surface, no light is reflected to the IR receiver, and its output is high.

The voltage regulator included on the PCB limits the power to the Infrared Line Follower’s circuitry to 3 V.

This means that a 5 V supply can safely be used with microcontrollers operating at 3.3 V.

Red LEDs located on the top of the board are wired to the output of each IR receiver, and the anode of

each LED is connected to power. When the IR LED is over a white surface, the low signal completes the

LED circuit and turns the LED on. Conversely, when the IR LED is over a black surface, the LED receives

dual high signals and the LED is off. This allows for easy visual feedback of the Infrared Line Follower’s

output states.

An onboard potentiometer also allows for the easy adjustment of the infrared frequency between 38 and

43 kHz. This allows the sensor to detect different colored lines, and also allows for the easy adjustment

of the sensor to different lighting conditions or mounting positions. For more information on how to

calibrate the sensor, see the Calibration section on page 8.

To isolate each IR senor and prevent false triggering, headers are placed between each IR emitter and

receiver pair.

Quick-Start Guide

Before using the Infrared Line Follower, it’s a good idea to test the sensor’s responsiveness in the area

intended for use. This section includes instructions for mounting and testing the Infrared Line Follower on

your Boe-Bot or Stingray robot, as well as for calibrating it in your lighting conditions. In order to use the

example code below, you will need a strip of black electrical tape on white paper.

Boe-Bot Assembly Instructions

To mount the Infrared Line Follower on your Boe-Bot robot, you will need the following materials:

(2) 7/8" 4-40 pan-head screws

(2) 1/4" 4-40 pan-head screws

(2) 1" round standoffs

(2) 1/2" round spacers

Step 1

Insert the 7/8" screws through the top of the Boe-

Bot chassis through the left and right slots at the

front.

Step 2

On the underside of the chassis, slip on the 1/2"

unthreaded spacer on each screw, followed by the

1" standoff. Don’t tighten the standoff completely

to allow for easier alignment of the Infrared Line

Follower’s mounting holes in the next step.

Step 3

Align the threaded standoffs with the mounting

holes on the Infrared Line Follower and use the

1/4" screws to secure the sensor to the screws.

The Infrared Line Follower should be facing

downward, with the headers pointing toward the

tail wheel.

Stingray Assembly Instructions

To mount the Infrared Line Follower on your Stingray, you will need the following materials:

(2) 7/8" 4-40 pan-head screws

(2) 1/2" round spacers

(2) 4-40 x 3/8" nuts

Step 1

Remove the front Stingray plate and insert the 7/8"

screws through the top of the chassis through the

front slot.

Step 2

On the underside of the chassis, slip on the 1/2"

unthreaded spacer on each screw.

Step 3

Align the screws with the mounting holes on the

Infrared Line Follower and use the nuts to secure

the sensor to the screws. The Infrared Line

Follower should be facing downward, with the

headers pointing toward the tail wheel.

Pin Definitions

Pin Name Type Function

1 GND G Ground -> 0V

2 Vdd P Supply Voltage

3 EN I Enable pin, pull low for low-power mode

4 OUT0 O Output state of IR receiver 0

5 OUT1 O Output state of IR receiver 1

6 OUT2 O Output state of IR receiver 2

7 OUT3 O Output state of IR receiver 3

8 OUT4 O Output state of IR receiver 4

9 OUT5 O Output state of IR receiver 5

10 OUT6 O Output state of IR receiver 6

11 OUT7 O Output state of IR receiver 7

Pin Type: P = Power, G = Ground, I = Input, O = Output

Quick-Start Circuit

The circuit pictured can be used with the example code below, as well as for the line following code

included at the end of this document.

Note: In order to use this sensor with the Stingray, you will need to bypass the voltage translators on

the Propeller Robot Control Board. The Infrared Line Follower has a 3 V onboard regulator, and the

Propeller Robot Control Board’s translators will interfere with signals coming from the sensor.

For instructions on how to disable the translators, see the documentation available on the Propeller Robot

Control Board’s product page. Go to www.parallax.com and search 28230.

Figure 1: Infrared Line Follower Quick-Start Circuit

BASIC Stamp 2 Example Code

The program InfraredLineFollower_Simple.bs2 will test the Infrared Line Follower sensors before they’re

used in a line-following application. Follow the instructions below to test that all 8 sensors are working

correctly.

Affix a 3/4" piece of electrical tape on a white piece of paper.

Enter & run InfraredLineFollower_Simple.bs2 (below).

Place sensor S0 over the electrical tape and the other sensors over the white paper.

The Debug Terminal should read %00000001 and the S0 LED should be off.

Repeat this process until all eight sensors are tested.

If your sensor doesn’t display a logical 1 when over a black surface and a logical 0 when over a white

surface, check your connections and/or try adjusting the frequency in the Calibration section on page 8.

' InfraredLineFollower_Simple.bs2

' Displays output states of the Infrared Line Follower using the Debug Terminal.

' {$STAMP BS2}

' {$PBASIC 2.5}

state VAR Byte

state = INL ' Read input state of pins 0-7

DEBUG HOME, "state = %", BIN8 state ' Display states on Debug Terminal

LOOP

Propeller P8X32A Example Code

The program below will test the Infrared Line Follower sensors before they’re used in a line-following

application. Follow the instructions below to test that all 8 sensors are working correctly.

Affix a 3/4" piece of electrical tape on a white piece of paper.

Enter & run InfraredLineFollower_Simple.spin.

Place S0 over the electrical tape, and the other sensors over the white paper.

The Parallax Serial Terminal should read %00000001 and the S0 LED should be off.

Repeat this process until all eight sensors are tested.

If your sensor doesn’t display a logical 1 when over a black line and logical 0 when over a white line,

check your connections and/or try adjusting the frequency in the Calibration section on page 8.

'' InfraredLineFollower_Simple.spin

'' Displays output states of the Infrared Line Follower using the Parallax Serial Terminal.

_clkmode = xtal1 + pll16x

_xinfreq = 5_000_000

VAR

byte state

OBJ

pst : "Parallax Serial Terminal"

PUB Main

outa[0..7]~ ' Sets pins 0-7 as input

pst.start(115_200) ' Initialize Parallax Serial Terminal

waitcnt(clkfreq + cnt)

repeat

state := ina[7..0] ' Read the states of pins 0-7

pst.home ' Set cursor to upper left corner

pst.bin(state, 8) ' Display states in PST

waitcnt(clkfreq/200 + cnt)

Calibration

Different lighting conditions, mounting positions or changes in temperature may require different

frequency settings. For this reason, the Infrared Line Follower has a user selectable infrared frequency

range of 38-43 kHz using an onboard potentiometer. If you are having problems reading a line when

running the test code, place all IR detectors over a black surface and gently adjust the onboard

potentiometer until all eight red LEDs are off.

Note: A small flathead screwdriver is required to adjust the frequency range. The Parallax screwdriver

included in the Boe-Bot and Stingray robot kits is usually sufficient.

Boe-Bot Robot Line Following Code

The code below can be used for simple Boe-Bot line following applications, and is compatible with the

circuit shown in Figure 1. Keep in mind that this is not the most robust line following code, which can and

should be expanded to better fit your needs.

' InfraredLineFollower_BoeBot.bs2

' Simple line following Boe-Bot code using the Infrared Line Follower.

' {$STAMP BS2}

' {$PBASIC 2.5}

SELECT INL ' Select line follower states

CASE %11000000, %11100000 ' Pivot right

PULSOUT 13, 650

PULSOUT 12, 650

CASE %01100000, %01110000 ' Curve right

PULSOUT 13, 700

PULSOUT 12, 650

CASE %00110000 ' Slight right

PULSOUT 13, 750

PULSOUT 12, 650

CASE %00111000 ' Adjust right

PULSOUT 13, 800

PULSOUT 12, 650

CASE %00011000 ' Straight

PULSOUT 13, 850

PULSOUT 12, 650

CASE %00011100 ' Adjust left

PULSOUT 13, 850

PULSOUT 12, 700

CASE %00001100 ' Slight left

PULSOUT 13, 850

PULSOUT 12, 750

CASE %00000110, %00001110 ' Curve left

PULSOUT 13, 850

PULSOUT 12, 800

CASE %00000011, %00000111 ' Pivot left

PULSOUT 13, 850

PULSOUT 12, 850

ENDSELECT

LOOP

Stingray Robot Line Following Code

The line following code included below is ideal for longer courses with wide-radius turns, and is

compatible with the circuit shown in Figure 1.

This code was written to be used as a skeleton for higher-precision line following applications using PID

and/or other control algorithms.

'' InfraredLineFollower_Stingray.spin

'' Simple line following code compatible with the Parallax Stingray Robot, best used

'' on longer courses with wide-radius turns

CON

_clkmode = xtal1 + pll16x

_xinfreq = 5_000_000

MotorA = 25 ' Motor A connected to P25

MotorB = 26 ' Motor B connected to P26

VAR

byte DutyCycleA, DutyCycleB, state

OBJ

PWM : "PWM_32_V2.spin"

PUB Main

PWM.Start ' Start PWM object

dira[7..0]~ ' Set pins 7..0 as input

repeat

state := ina[7..0] ' Set input states to variable state

case state

%00000011, %00000001, %00000010: ' Pivot left

DutyCycleA := 65

DutyCycleB := 0

%00000111, %00000110, %00000100: ' Slight left

DutyCycleA := 60

DutyCycleB := 0

%00001110, %00001100: ' Adjust left

DutyCycleA := 55

DutyCycleB := 0

%00011100, %00011000, %00111000: ' Straight

DutyCycleA := DutyCycleB := 50

%01110000, %00110000: ' Adjust right

DutyCycleA := 0

DutyCycleB := 55

%11100000, %01100000, %0010000: ' Slight right

DutyCycleA := 0

DutyCycleB := 60

%11000000, %01000000, %10000000: ' Pivot right

DutyCycleA := 0

DutyCycleB := 65

other: ' Anything else, slowly move forward

DutyCycleA := DutyCycleB := 20

PWM.Duty(MotorA, DutyCycleA, 50) ' Adjust motor speeds

PWM.Duty(MotorB, DutyCycleB, 50)

Mouser Electronics

Authorized Distributor

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Parallax:

28034

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