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Programming 201:�Using Force and Distance Sensors

LEGO® Education SPIKETM Prime Word Blocks

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Coach Series

Disclaimer: This private training is provided by the North Texas Region and is not affiliated or operated by the LEGO® Group or by FIRST ®. The LEGO Group® and FIRST® are not responsible for any of its activities.

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Learning Objectives

  • Familiarization with the SPIKE™ Prime Force sensor.
  • How to use the Force sensor with the Gyro sensor to control movement.
  • Familiarization with the SPIKE™ Distance sensor.
  • How to use the Distance sensor with the Gyro sensor to control movement.

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Recommended Prerequisites:

Programming 101 – Introduction and Common Practices

Programming 101 – Basic Movement

Programming 201 – Line following, Variables and My Blocks

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SPIKE™ Sensor Overview

MEDIUM MOTOR

COLOR SENSOR

LARGE MOTOR

DISTANCE SENSOR

FORCE SENSOR

SPIKE™ HUB

GYRO SENSOR

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Sensors included in the core and expansion sets

Sensor

Core Set (45678)

Expansion Set (45680)

Force sensor (force, touch)

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Color sensor (color, light)

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1

Distance sensor

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Medium motor (rotation)

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Large Motor (rotation)

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1

SPIKE Prime Hub (gyro, accelerometer)

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0

https://education.lego.com/en-us/product-resources/spike-prime/downloads/technical-specifications/

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Force Sensor – Modes and Specifications

The three Force sensor modes are:

  • Pressed – detects a slight tap of the sensor
  • Hard-pressed – pressing the sensor in about 60%
  • Released – hold the sensor in and release it any amount

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Force Sensor – Modes and Specifications

  • Sensor sample rate: 100Hz
  • Touch sensing activation zone: 0 to 2 mm
  • Force sensing activation zone: 2 to 8 mm
  • Activation on force: 2.5 to 10 newtons
  • Resolution 0.1 newtons
  • Accuracy +/1 0.65 newtons

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Force Sensor – Pseudocode

  1. Set standard robot movement.
  2. Set % speed.
  3. Start moving straight.
  4. Wait until the Force Sensor is pressed.
  5. Stop moving.

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Force Sensor – Basics

  • Set standard movement:
    • Set movement motors to [input].
    • Set 1 motor rotation to [input] [cm/in] moved.
    • Set movement motors to [brake/hold position/coast at stop.
  • From the More Movement group, select and drag the “start moving at [input] [input] % power” word block to the Programming canvas and insert into the “set movement motors to” word block. Set both motor powers to 30%.

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Force Sensor – Basics

  • From the Control group, select and drag the “wait until [input]” word block to the Programming canvas and connect to the “start moving at [input] [input] % power” word block.
  • From the Sensors group, select and drag the “Force Sensor [port] is [pressed]?” input to the Programming canvas and insert into the “wait until” word block input.
  • Set Force Sensor “port” and set to “pressed”.

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Force Sensor – Basics

  • From the Movement group, select and drag the “stop moving” word block to the Programming canvas and it to the “wait until” word block.

Download and test your code.

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Control Movement with Force and Gyro Sensors

Using the Gyro sensor to move straight to the target and the Force sensor to stop at the target

Create a My Block named “ForceSensor” with three inputs and labels:

    • Input: “%”, Label: “Power”.
    • Input: “Degree”, Label: “Direction”.
    • Input: “Factor”, Label: “KP”.

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Control Movement with Force and Gyro Sensors

  • From the Control group, select and drag the “repeat until [input]” word block to the Programming canvas and connect to the “ForceSensor” My Block.
  • From the Sensors group, select and drag the “Force Sensor [port] is [pressed]?” input to the Programming canvas and insert into the “wait until” word block input. Set the sensor port.
  • Set Force Sensor settings to “port” and set to “pressed”.

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Control Movement with Force and Gyro Sensors

  • From the Variables group, select and drag the “set [Variable] to [input]” variable block to the Programming canvas and insert into the “repeat until” word block. Set to “Correction”.
  • From the Operator group, select and drag the “*” (multiply) operator block to the Programming canvas and insert into the “Correction” variable block input.
  • From the Operator group, select and drag the “-” (subtract) operator block to the Programming canvas and insert into the “*” (multipy) operator block second input.

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Control Movement with Force and Gyro Sensors

  • From the My Block group, select the factor (KP) input and drag to the first input in the “*” (multiply) operator block position 1.
  • From the My Block group, select the Degrees (Direction) input and drag to the first input in the “-” (subtract) operator block.
  • From the Sensor group, select and drag the “Gyro [pitch] angle” input to the Programming canvas and insert into the “-” (subtract) operator block second position.

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Control Movement with Force and Gyro Sensors

  • From the More Movement group, select and drag the “start moving at [input] [input] % power” input to the Programming canvas and insert into the “repeat until” operator block after the “set [Variable] to [input].
  • From the Operator group, select and drag the “+” (plus) operator block to the Programming canvas and insert into the “start moving at” variable block first input.
  • From the Operator group, select and drag the “-” (subtract) operator block to the Programming canvas and insert into the “start moving at” operator block second input.

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Control Movement with Force and Gyro Sensors

  • From the My Block group, select the % (Power) input and drag to the first input in the “start moving at / [input] + [input]” operator block position 1.
  • Repeat for the [input] - [input] operator block first position.
  • From the Variable group, select and drag the “Correction” variable input to the “start moving at [input] [input]” word block, “+” operator second position.
  • Repeat for the “-” operator block second position.

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Control Movement with Force and Gyro Sensors

  • From the Movement group, select and drag the “stop moving” word block to the Programming canvas and it to the “wait until” word block.

Write a program to test your code.

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Distance Sensor - Basics

  • Code is the same as the Force sensor except for the “wait until” operator block.
  • Copy the Force sensor code.
  • Delete the Force sensor operator input.
  • From the Sensors group, select and drag the “Ultrasonic Sensor [port] is [closer than] [input] [cm/in]?” input to the Programming canvas and insert into the “wait until” word block input.

Download and test your code.

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Distance Sensor - Description

  • The Distance Sensor measures distance to an object or surface using ultrasound. The sensor sends a high frequency sound waves that bounce off an object in range, and measuring how long it takes the sound to return to the sensor.
  • The Distance Sensor can also be used as a light source, with four LED segments around the "eyes" that can be controlled individually.
  • Distance Sensing from 50 to 2000 mm
  • Fast distance sensing from 50 to 300 mm
  • White light output around the sensor “eyes” divided into four segments – two upper and two lower segments. (Lower segments are Python only).

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Control Movement with Distance and Gyro Sensors

Create a My Block named “ForceSensor” with four inputs and labels:

    • Input: “Degree”, Label: “Direction”
    • Input: “%”, Label: “Power”
    • Input: “Factor”, Label: “KP”
    • Input: “CM”, Label: “DistanceFrom”

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Control Movement with Distance and Gyro Sensors

  • From the Control group, select and drag the “repeat until [input]” word block to the Programming canvas and connect to the “UltrasonicMove” My Block.
  • From the Sensors group, select and drag the “Distance Sensor [port] is [closer than/farther than/exactly at] [input] [cm/inch]?” input to the Programming canvas and insert in the “repeat until” word block input.

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Control Movement with Distance and Gyro Sensors

  • From the Variables group, select and drag the “set [Variable] to [input]” variable block to the Programming canvas and insert into the “repeat until” word block. Set to “Correction”.

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  • From the Operator group, select and drag the “*” (multiply) operator block to the Programming canvas and insert into the “Correction” variable block input.
  • From the Operator group, select and drag the “-” (subtract) operator block to the Programming canvas and insert into the “*” (multipy) operator block second input.

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Control Movement with Distance and Gyro Sensors

  • From the My Block group, select the factor (KP) input and drag to the first input in the “*” (multiply) operator block position 1.
  • From the My Block group, select the Degrees (Direction) input and drag to the first input in the “-” (subtract) operator block.
  • From the Sensor group, select and drag the “Gyro Sensor [pitch/roll/yaw] angle” input to the Programming canvas and insert into the “-” (subtract) operator block second input position. Set to “yaw”.

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Control Movement with Distance and Gyro Sensors

  • From the More Movement group, select and drag the “start moving at [input] [input] % power” input to the Programming canvas and insert into the “repeat until” operator block after the “set [Variable] to [input].
  • From the Operator group, select and drag the “+” (plus) operator block to the Programming canvas and insert into the “start moving at” variable block first input.
  • From the Operator group, select and drag the “-” (subtract) operator block to the Programming canvas and insert into the “start moving at” operator block second input.

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Control Movement with Distance and Gyro Sensors

  • From the My Block group, select the % (Power) input and drag to the first input in the “start moving at / [input] + [input]” operator block first position. Repeat for the [input] - [input] operator block first position
  • From the Variable group, select and drag the “Correction” input to the “start moving at [input] [input]” word block, “+” operator second position. Repeat for the “-” operator second position.

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Control Movement with Distance and Gyro Sensors

  • From the Movement group, select and drag the “stop moving” word block to the Programming canvas and it to the “repeat until” word block.

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Control Movement with Distance and Gyro Sensors

Write a program to test your code.

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20

.4

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.4 x (0 – 0) = 0

Current yaw reading is 0

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.4

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20 + 0 = 20

20 - 0 = 20

Both motors at same speed = robot move straight

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Everything is awesome!

-Emmet Joseph Brickowski

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