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Lecture 1: Your Boe-Bot's Servo Lecture 1: Your Boe-Bot's Servo MotorsMotors

Presentation based on:

"Robotics with the Boe-Bot"By Andy LindsayParallax, Inc

Presentation developed by:Presentation developed by:

Martin A. HebelMartin A. HebelSouthern Illinois University CarbondaleSouthern Illinois University CarbondaleCollege of Applied Sciences and ArtsCollege of Applied Sciences and ArtsElectronic Systems TechnologiesElectronic Systems Technologies7/6/04

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Continuous Rotation ServoContinuous Rotation ServoUsed to provide drive motion for the Bot.

Standard Servo: Used for positioning, such as with RC airplanes rudder and flaps.Continuous Rotation Servo: Rotate in a certain direction and speed.

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Tracking TimeTracking Time

PAUSE is used to have the BASIC Stamp wait a short amount of time.PAUSE duration• Duration is in milliseconds (mS) or

1/1000th of a second, 1-65535

PAUSE 1000

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Repeating ActionsRepeating Actions

A DO….LOOP is used to repeat a sequence of commands.DO

'Commands to performLOOP

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Servo SignalsServo Signals

Servos are controlled with a high pulse lasting a short time, and repeated.

The PULSOUT instruction can be used to send a short pulse.PULSOUT Pin, Duration• Pin: Pin device is connected to.• Duration: Time in 2S (microsecond)

intervals, 1-65535. Microsecond = 1 millionth of a second.

PULSOUT 12, 1PULSOUT 13, 2

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Servo SignalsServo Signals

Typical servos require a pulse of 1mS to 2mS to define the direction/position.

A 20mS pause be between each pulse.

What values of PULSOUT are in the valid range?

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Connecting the ServosConnecting the Servos

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Centering the ServosCentering the Servos

The pulse width defines the direction and speed of the servo motor.• 1000 – Maximum speed one direction• 750 – Stopped• 500 – Maximum speed other direction

Use the servo center programs to ensure it is stopped at 750.

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Storing and Counting ValuesStoring and Counting Values

Variable are used to store valuesVariables much be declared prior to

being used. Declaring a variable is giving it a name, and a size to hold.VariableName var Size

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DEBUG ? is short hand to display the value of a variable or pin.

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Counting and Controlling Counting and Controlling RepetitionsRepetitionsFOR…NEXT loops can be used to

control the number of repetitions a segment of code takes.

FOR StartValue TO EndValue {STEP StepValue}…NEXT

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What will this code do?What will this code do?

Freq VAR Word

DO FOR Freq = 1000 to 5000 Step 100

DEBUG ? Freq FREQOUT 4, 100, Freq

TOGGLE 12 TOGGLE 13NEXT

LOOP

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Testing ServosTesting Servos

To control the servo, send a series of pulses with values between 500 to 1000 (1-2mS)

Changing the value will change the direction and speed to some extent.

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FOR…NEXT to Control Servo Run FOR…NEXT to Control Servo Run TimeTimeThe FOR…NEXT Loop can be used to

control how long to drive a servo.

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ReviewReview

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