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Rotational Sensors

The rotation sensor can measure the rotationof the wheels.

By measuring the rotation of the wheels, and knowing the diameter of the wheels, we can measure and control how far the robot travels.

Remember: The rotation sensor has 16 counts per rotation.

Robotics Academy 2002. All Rights Reserved.

Geometry Review

The Diameter isthe distance across the circlethrough its center.It is twice the radius.

The Circumferenceis the distance allthe way around the circle.

Robotics Academy 2002. All Rights Reserved.

Geometry Review

1 turn of the wheel 1 turn of the wheel is called is called 1 revolution1 revolution

How big is How big is 1 1 revolution?revolution?

It is as long as the It is as long as the circumference of the circumference of the wheel!wheel!

How do I calculate the circumference (1 revolution)???

CCircumference = x Diameter

= 3.14= 3.14

How do I calculate the circumference (1 revolution)???

CCircumference = 3.143.14 xx

RRevolution = 3.143.14 xx

What about 1 revolution? How do I calculate that?

Let’s Practice!Let’s Practice!CCircumference = 3.143.14 xx

The diameter of my wheel is 2 cm

The diameter of my wheel is 2 cm

C = 3.14 x 2C = 3.14 x 2 6.28 cm6.28 cm

Let’s Practice!Let’s Practice!CCircumference = 3.143.14 xx

The diameter of my wheel is 3.5 cm

The diameter of my wheel is 3.5 cm

C = 3.14 x 3.5C = 3.14 x 3.5 10.99 cm10.99 cm

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Circumference

Question: When this robot’s wheels make one revolution, how far does the robot travel?

Answer: One circumference of the wheel!

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Count or Click

The rotation sensor has 16 counts per rotation.

The rotation sensor has 16 counts per rotation.

1 count or click

2nd count or click

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How big is 1 click?

Circumference Circumference

1616

Let’s Practice!Let’s Practice!1 Click1 Click = CC : 16: 16

The diameter of my wheel is 3 cm

The diameter of my wheel is 3 cm

C = 3.14 x 3C = 3.14 x 3

0.58… cm0.6 cm

0.58… cm0.6 cmClick = 9.42 : 16Click = 9.42 : 16

9.42

Let’s Practice!Let’s Practice!1 Click1 Click = CC : 16: 16

The diameter of my wheel is 2.5 cm

The diameter of my wheel is 2.5 cm

C = 3.14 x 2.5C = 3.14 x 2.50.4906…

cm0.5 cm

0.4906… cm

0.5 cmClick = 7.85 : 16Click = 7.85 : 16

7.85

Let’s Solve Some Problems!Let’s Solve Some Problems!

The diameter of my wheel is 4 cm, the length of the table is 50 cm

The diameter of my wheel is 4 cm, the length of the table is 50 cm

C = 3.14 x 4C = 3.14 x 4

63.7.. clicks63.7.. clicks

Click = 12.56 : 16Click = 12.56 : 16

12.56 cm

Determine how many clicks it will take to drive your robot on the side of your table.

0.785 cm

50 cm : 0.785 cm50 cm : 0.785 cm

Let’s Solve Some Problems!Let’s Solve Some Problems!

The diameter of my wheel is 3 cm, the length of the table is 104 cm

The diameter of my wheel is 3 cm, the length of the table is 104 cm

C = 3.14 x 3C = 3.14 x 3

176.3...clicks

176.3...clicks

Click = 9.42 : 16Click = 9.42 : 16

9.42 cm

Determine how many clicks it will take to drive your robot on the side of your table.

0.59 cm

104 cm : 0.59 cm104 cm : 0.59 cm

Let’s Solve Some Problems!Let’s Solve Some Problems!

The diameter of my wheel is 1.5 cm, the length of the table is 104 cm

The diameter of my wheel is 1.5 cm, the length of the table is 104 cm

C = 3.14 x 1.5C = 3.14 x 1.5

358.6 clicks358.6 clicks

Click = 4.71 : 16Click = 4.71 : 16

4.71 cm

Determine how many clicks it will take to drive your robot on the side of your table.

0.29 cm

104 cm : 0.29 cm104 cm : 0.29 cm

Extra Info

Robotics Academy 2002. All Rights Reserved.

Example

The diameter of this wheel is 8 cm.

C = x D. That means its circumference is 8 x 3.14 = 25.1 cm.The rotation sensor has 16 counts per rotation.

That means the robot will travel25.1 / 16 = 1.57 cm per sensor count.