UsingUltrasonic.md

@activities true

@explicitHints true

:MOVE Motor Ultrasonic Sensor

Introduction

Introduction Step @unplugged

Learn how to use the :MOVE Motor's Ultrasonic Distance Sensor to detect objects and stay a certain distance from them.

Step 1

First, let's use the sensor to display the distance to an object. Start by creating a variable called ||variables:distance|| and place the ||variables:set distance to|| block in the ||basic:forever|| loop. Make ||variables:distance|| equal to ||Kitronik_Move_Motor.measure distance|| by dropping the block inside (this can be found in the ||Kitronik_Move_Motor.Sensors|| section of the ||Kitronik_Move_Motor.MOVE Motor|| category).

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
})

Step 2

Now add a ||basic:show number|| block below the set variable block. Place the variable ||variables:distance|| inside the ||basic:show number|| block.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    basic.showNumber(distance)
})

Step 3

If you have a @boardname@ connected, click |Download| to transfer your code and switch on :MOVE Motor. Then move a box in front of the :MOVE Motor and see the micro:bit display show the distance to the box.

Follow the Object

Follow the Object @unplugged

Now we know the distance to the box, we can use that to drive the motors and make the :MOVE Motor follow the box if it moves away.

Step 1

Start by removing the ||basic:show number|| block, then add an ||logic:if|| statement, with ||variables:distance|| ||logic:> 10|| as the test condition. Inside the ||logic:if|| block, make the :MOVE Motor ||Kitronik_Move_Motor.move forward|| if the condition is met.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    }
})

Step 2

If you have a @boardname@ connected, click |Download| to transfer your code and switch on :MOVE Motor. Place a box in front of the :MOVE Motor and, as you move it away, see the :MOVE Motor follow. But there is a problem. We only start the motors!

Step 3

This means the motors start as soon as the box is more than 10cm away, but they never stop, so the :MOVE motor will just keep going. We need to stop when we are closer to the object. So, click the ||logic:+|| icon to add an ||logic:else|| statement and place a ||Kitronik_Move_Motor.stop|| block inside.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    } else {
        Kitronik_Move_Motor.stop()
    }
})

Step 4

If you have a @boardname@ connected, click |Download| to transfer your code and switch on :MOVE Motor. As before, place a box in front of the :MOVE Motor and see it follow as the box is moved away, but this time, it stops when it gets within 10cm.

Step 5

Currently, the code only allows the :MOVE Motor to follow the object if it moves away. If the object comes closer, we want to reverse the :MOVE Motor. To do this, we need another test condition to check whether the distance is less than 10cm. If it is, we reverse.

Click the ||logic:+|| icon on the ||logic:if else|| block to add an ||logic:else if|| statement. Put in ||variables:distance|| ||logic:< 10|| as the test condition, and make the :MOVE Motor ||Kitronik_Move_Motor.reverse|| if the condition is met.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    } else if (distance < 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Reverse, 100)
    } else {
        Kitronik_Move_Motor.stop()
    }
})

Step 6

If you have a @boardname@ connected, click |Download| to transfer your code and switch on :MOVE Motor. Now try out making the :MOVE Motor drive forwards and backwards as you move the box.

Free Roaming

Free Roaming @unplugged

Great! The :MOVE Motor can now move forwards and backwards, keeping the same distance from the box as you move it. But it can only move in a straight line. It would be much better if it could drive around by itself and not crash into things...

Step 1

To turn :MOVE Motor into a free roaming robot, we just need to make a few changes to our code. Begin by moving the ||Kitronik_Move_Motor.stop|| block to the ||logic:else if|| section, above the ||Kitronik_Move_Motor.reverse|| block. Then, click the ||logic:-|| icon on the ||logic:else|| statement to remove it.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    } else if (distance < 10) {
        Kitronik_Move_Motor.stop()
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Reverse, 100)
    }
})

Step 2

Next, add a 500ms ||basic:pause|| after the ||Kitronik_Move_Motor.stop||, and a 1 second ||basic:pause|| after the ||Kitronik_Move_Motor.reverse|| block. We also want to slow :MOVE Motor down a bit when it's avoiding obstacles, so change the ||Kitronik_Move_Motor.reverse|| speed to 50.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    } else if (distance < 10) {
        Kitronik_Move_Motor.stop()
        basic.pause(500)
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Reverse, 50)
        basic.pause(1000)
    }
})

Step 3

Finally, we need to make :MOVE Motor turn away from the obstacle it has detected. Add a ||Kitronik_Move_Motor.spin left at speed 50|| block to the ||logic:else if|| section, followed by another 500ms ||basic:pause|| and a ||Kitronik_Move_Motor.stop|| block.

~ tutorialhint

let distance = 0
basic.forever(function () {
    distance = Kitronik_Move_Motor.measure()
    if (distance > 10) {
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Forward, 100)
    } else if (distance < 10) {
        Kitronik_Move_Motor.stop()
        basic.pause(500)
        Kitronik_Move_Motor.move(Kitronik_Move_Motor.DriveDirections.Reverse, 50)
        basic.pause(1000)
        Kitronik_Move_Motor.spin(Kitronik_Move_Motor.SpinDirections.Left, 50)
        basic.pause(500)
        Kitronik_Move_Motor.stop()
    }
})

Step 4

CODING COMPLETE! If you have a @boardname@ connected, click |Download| to transfer your code and switch on :MOVE Motor. Now put :MOVE Motor on the floor and watch it roam around avoiding obstacles.