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Ultrasonic Sensor

SensorBot

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Ultrasonic Sensors

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Ultrasonic

The ultrasonic sensor sends a sound wave (that you can’t hear) and counts how long it takes for the sound to bounce back.

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This side Transmits the sound wave.

This side Receives the reflected sound wave.

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How it works

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Detected

Not Detected

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Echolocation

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Connect Ultrasonic Sensor

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Power

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Ground

(GND)

VCC

(5 Volts)

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Communication

Pins that connect to the Arduino

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Ground

(GND)

VCC

(5 Volts)

Trigger

Echo

Trigger sends signals to the outside world

Echo receives signals from the outside world

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Connect Ultrasonic

Materials Needed:

Assembled Chassis
Ultrasonic Sensor
Jumper wires (red, orange, blue, black)

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Connect Wires to Sensor

VCC – Red Wire

Trig – Orange Wire

Echo – Blue Wire

Gnd – Black Wire

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Connect Wires to PCB

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Red Wire – 5V

Orange Wire – D12

Blue Wire – D11

Black Wire – GND

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Check Your Work

Trace your wires!

VCC – Red Wire – 5V

Trig – Orange Wire – D12

Echo – Blue Wire – D11

Gnd – Black Wire – GND

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Place the ultrasonic sensor in the mount

Place the ultrasonic sensor into the mount with the wires pointing up.

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Video

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Program Ultrasonic Sensor

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It’s Time to Code!

Open Google Chrome (web browser)

Navigate to www.tinkrcode.com

Click “Have a Code?”

Log in with your Project and Class codes.

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Open Your Program

Open your program.

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Connect to Bluetooth

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1. Click Connect.

2. Choose the number that is on your Project Sticker and click Pair.

3. Green means connected!

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Sensor Setup

From the sensor drawer, get a sensor setup block, and add it the setup part of your program.

Change the Trigger Pin to D12 & the Echo Pin to D11.

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Ultrasonic Distance

Pull this block from the Sensor drawer.

This block checks to see if the Ultrasonic sensor detects something.

If it has detected something, it tells you how far away that object is.

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Print the Distance

Drag a Print Number block from the Serial Print drawer.
Remove the 0 and snap the blocks together.

Put the resulting block into the Loop part of your program.

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throw this away

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Sensor Data

In the Serial Print window, what are the numbers?

What do the larger numbers mean?

What are the smaller numbers?

What does 1000 mean?

What happened when you moved your hand to the side of the sensor?

What happened when you tilted your hand so that it was no longer parallel to the sensor?

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Where the Sensor Fails

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Making decisions

It will have to make decisions about how to move based on what it ‘sees.’

For this, we will need to use a conditional statement.

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We want our robot to react to objects in the environment.

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Conditionals

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Making decisions

This section is the conditional (If/Then/Else statement)

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Conditionals in TinkRcode

If chance of rain is > 80%

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Take the bus home

Go to soccer practice

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Combining conditionals

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What does it do when the house is too hot?

What does it do when it’s too cold?

What does it do when the temperature is just right?

Putting one conditional in another is called “nesting”

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Pointers for Slide Delivery

Sometimes our robots will need more than one test.
Ask students to walk through the diagram.

If: The temp is > 80 (Test)

Then: Turn on the A/C

Else: (the temp is <80)

If: the temp is <65 (Test)

Then: Turn on heat

Else: (temp is between 65 & 80): Turn off the heat and A/C

Slide Clicks

If it is too hot, it turns on the A/C.
If it is too cold, it turns on the heat.
When it is good temp, it turns both off.

Often we want to make robots that can make more complex decisions between 3 or more choices, and we can use if and else statements to construct these more complex choices by putting one conditional inside of another, which we call nesting.

A thermostat is a good example of a system that has to make one of three decisions: Depending on the temperature it can turn on the furnace to make the house warmer, or turn on the air conditioning to lower the temperature, or it can turn both of those off if the house is a comfortable temperature.

The flow chart shows how it makes these choices. First it decides if the air conditioning should be on by checking if the temperature is over 80 degrees. If the air conditioner shouldn't be on, then the thermostat does a second check to see if the furnace should be on.

It's really important to notice that there's a gap between the two limits that cause action so that there's actually an area where the thermostat decides to do nothing. We call this area the Goldilocks zone, and if it didn't exist, then the air conditioner and furnace would constantly be fighting each other as one triggers the other one to act.

Image Link: https://i.stack.imgur.com/FPVOp.png

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How would this look in TinkRcode?

Algorithm

TinkRcode

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Else If

Two If/Else statements

Else if

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Planning the Conditional

What do we want OUR conditionals to be?

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Test:

IF there is an object < 10cm away

Then:

Spin right

Else:

Go straight

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Build the Test

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Test:

IF there is an object < 10cm away

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Put it together

What does this code do?

How will the bot behave?

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Challenges

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Challenge #1: Avoid It

Challenge Name

Avoid It

Challenge Objective

Create a subroutine containing code that will make the bot back up, spin right, and then stop if the Ultrasonic Sensor detects an object.
Name it “Avoid It”.

Challenge Notes

You’ll need to decide the value for the distance from the ultrasonic sensor to use.
How long to backup and spin for.
Put the “Forward Slow” subroutine and the “Avoid It” subroutine in the loop to test it out.

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Challenge #2: I’m not touching you!

Challenge Name

I’m not touching you!

Challenge Objective

Code your bot to move forward whenever it’s far away from your hand, back up whenever it’s too close, and stand still whenever it’s in between.

Place it in a subroutine named “Not Touching You”

Challenge Notes

You’ll need to decide what the thresholds should be.
How close can your thresholds be to each other?
How close can your robot get to you without touching you?

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Challenge #3: Wall Following

Challenge Name

Wall Following

Challenge Objective

Code your bot to move along a wall, by curving toward the wall when it’s too far away and then curving away from the wall when the robot gets too close.

Challenge Notes

You may find success by speeding up and slowing down the outside wheel.

Use a servo command to point the ultrasonic sensor to the side.

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click to start

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Wall Following Demo

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Wall Following Parameters

Parameters:

Overall speed
Angle of turns

How different are the speeds between the 2 motors.

Direction of the ultrasonic sensor
Distances from the wall to guide direction of bot.
Addition of delays or stops?

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Solutions

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Challenge #1 Solution: Avoid It

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Challenge #2 Solution: I’m not touching you

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Challenge #3 Solution: Wall Following Setup

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If you are following a wall to the bot’s right, turn the ultrasonic sensor to the right.

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Challenge #3 Solution: Wall Following Loop

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Pointers for Slide Delivery

Forward right: Veering to the right. Notice the difference in motor speeds.
Forward left: Veering to the left
Forward slow: Going straight ahead slowly.

NOTE: If the bot needs a calibration offset, they should incorporate that into the motor speeds.

If the right motor is 7 units faster than the left, then you need to increase the right motor by 7.
i.e. to go straight it would be A: 117, B: 110.
If the calibration is off by a great amount, then you will have to alter the forward right & left speeds.
If the calibration is small, it may not matter.

Students may notice that the robot is not able to adjust its trajectory quickly enough over shorter distances.
It’s hard to see the individual adjustments that the robot is doing to stay straight. Try printing out the distance from the wall.

The next slide shows a solution that slows down the robot by introducing a short crawl.

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Wall Following using a Variable

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An optimization can be added to only read the sensor once per loop.

This speeds up the loop and allows the decisions to be based on one measurement.

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Challenge #3 Tip: Print out distance

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Challenge #3 Tip: Add Lights

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Wall Following Slowdown

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Subroutine

Put your code in a subroutine named “wall follow”.

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TinkRworks, Inc.

501 W Lake Street, Suite 106

Elmhurst, IL 60126

www.TinkRworks.com

Sparking CREATIVITY

Fostering INNOVATION

Sharpening PROBLEM-SOLVING skills

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