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Strawbees and Hummingbird

Hot glue a Strawbee to the Hummingbird servo motor, and then just start building!

 

 

 

 

You can also use Strawbees with the gear motor by gluing them to the plastic brick adaptor.

 

 

 

 

 

Try making a fun linkage with the Hummingbird and Strawbees!

 

 

 

 

Pro Tip: You can use just the tip of a Strawbee as a connector. This can help you to keep parts of your creation from colliding. In the video above, a small connector keeps the straw connected to the motor from hitting the stationary straw on the table.

News

Get a Grip!

Materials

  • computer with Birdbrain Robot Server and Scratch
  • plastic bottle
  • Hummingbird board
  • Vernier BTA Sensor Adapter for Hummingbird
  • 1-hole stopper with tapered valve
  • Vernier Gas Pressure Sensor
  • heavy-wall plastic tubing

Procedure

  1. Connect the plastic bottle to the pressure sensor as shown below.
  2. Connect the Vernier BTA sensor adapter to the Hummingbird. Then connect the pressure sensor to the adapter. The jumper on the adapter should be set to 0-5 V.
  3. To read a measurement from the pressure sensor, you will use the HB voltage block in Scratch. This block will read a voltage between 0 and 5 V.
  4. The Vernier manual for the pressure sensor provides a linear equation that you can use to convert voltage to pressure: pressure = 51.71*voltage – 25.86
  5. In this experiment, you will grip the bottle as hard as you can for 60 s. You want to record data during this time and compare the data from 0 -10 s with the data from 50 – 60 s. To do this, you will need to write a program that meets the following requirements:
    1. The program must record 480 pressure sensor measurements and store them in a list.
    2. The program should wait 0.125 seconds between measurements (so the program takes approximately 8 measurements per second).
    3. The program must use the function above to calculate the pressure based on the HB voltage block.
    4. The program should graph the pressure measurements to the screen. The pressure measurements should be scaled so that this graph occupies most of the screen. The stage backdrop should show appropriate axes for this graph.
    5. The program should calculate the mean pressure for the entire 60 s period and display this value for the user.
    6. The program should calculate the mean pressure during the period 0 – 10 s and display this value for the user.
    7. The program should calculate the mean pressure during the period 50 – 60 s and display this value for the user.
  6. Grip the bottle as hard as you can with one hand while you run your program. Remember not to start the program until you are gripping as hard as you can. Record your data in the table below.
  7. Repeat this process for your other hand. Record your data in the table.

Data

Processing the Data

  1. In the space provided in the data table, subtract to find the difference between your 0–10 s average and your 50–60 s average for each hand.
  2. Record the 0–60 s results for the other students in your group. Calculate and record your group average. Calculate and record the class average for 0–60 s.
  3. Which of your hands is stronger? Explain your decision.
  4. Did your gripping power increase or decrease during the 60 s period? Why did it change?
  5. How does your grip compare with the class average?
  6. What did you learn about your strength in this experiment? Were you surprised?

Extension

Can you motivate yourself (or someone else) to grip harder? Use lights, motors, and/or sounds to make a robot that does different things depending on how hard the person is gripping. For example, maybe more LEDs light up the harder the person grips. Does the average grip pressure increase when someone uses your device?

News

Where IS North?

Overview

Where IS north? It depends. Do you mean geographic north or magnetic north? The geographic (true) north pole is the point at 90° N latitude. It is aligned with the rotational axis of the Earth. The Earth is surrounded by a magnetic field with a north and south magnetic pole. The magnetic north pole is the point to which a compass needle points. It is currently in northern Canada, but moves at an average rate of 15 km per year due to complex fluid motion in the outer core of Earth. Depending on your location, the difference between magnetic north and geographic north, called magnetic declination, can range from 0° to 30°.

In this experiment, you will measure the magnetic field of the Earth. You will use this data to determine magnetic north. Knowing the direction of true north, you will calculate the magnetic declination at your location.

Materials

  • computer with Birdbrain Robot Server and Scratch
  • Hummingbird board
  • Vernier BTA sensor adapter for Hummingbird
  • Vernier Magnetic Field Sensor
  • glue gun
  • cardboard
  • rubber bands

Procedure

  1. Bend the magnetic field sensor so that the end is at a right angle to the handle of the sensor.
  2. Connect the Vernier BTA sensor adapter to the Hummingbird. Then connect the magnetic field sensor to the adapter. Set the switch on the magnetic field sensor to 0.3 mT (high amplification).
  3. You need to build a robot that will rotate the magnetic field sensor to a variety of angles between 0° and 360°. To do this, you should use two servo motors. One possible design is shown below. The top servo rotates from 0° to 180° while the bottom servo is at 0°. Then the bottom servo moves to 180°, and the top servo rotates from 0° to 180° again. In this way, the top plate can stop at any angle from 0° to 360°. There are other possible designs! Note: If you mount one servo on top of another, make sure that the axes of rotation of the two servos lie along the same line.
  4. Once you have a robot that can stop at angles from 0° to 360°, mount the magnetic field sensor on it in the orientation shown below. DO NOT use hot glue on the magnetic field sensor! You can use rubber bands to gently attach it to your robot.
  5. To read a measurement from the magnetic field sensor, you will use the HB voltage block. This block will read a voltage between 0 and 5 V.
  6. The Vernier manual for the magnetic sensor provides a linear equation that you can use to convert voltage to magnetic field strength (in millitesla): magnetic field = (0.16 mT/V)*voltage – 0.32 mT
  7. In this experiment, you need to record a number of magnetic field measurements. You should write a program that saves these measurements in a list. Your program should meet the following requirements:
    1. The magnetic field sensor should stop every 15° between 0° and 360°.
    2. At each stop, the program should record the angle in one list and the magnetic field sensor reading in another list.
    3. The program should graph the magnetic field measurements to the screen. The measurements should be scaled so that this graph occupies most of the screen.
  8. Look at your graph. Where is the magnetic field highest? This is the direction of magnetic north! Look through your lists to find the angle with the highest magnetic field. Be sure to record this value.

Processing the Data

  1. Consult a map to estimate the direction of north for your location. How does this compare to the direction you identified in this experiment? If a compass is available, use this to measure the direction of magnetic north and compare it to your results.
  2. The difference between the measured magnetic north and true north is called magnetic declination. What is the magnetic declination for your location? What modifications would be needed on a compass in your location to keep you on course when following a map?

Extensions

  1. Modify your program so that it automatically calculates the angle of magnetic north. Then make the robot point the magnetic field sensor in this direction. Use LEDs to show the user the direction of magnetic north.
  2. Research current theories on why the magnetic north pole moves.
  3. Scientists have found that the magnetic field of the Earth is continually changing. What would be the implications of a big change?
News

Robot Petting Zoo

  1. Introduction: Very briefly, introduce participants to the goals of the robot petting zoo. It may be helpful to use videos from this playlist above to show students the types of things that are possible. This is also a good time to show students the Hummingbird components and describe how they can be used to create robots that sense, think, and act.
  2. Learning to Build: Jumping right into a building activity capitalizes on student enthusiasm and enables them to immediately take ownership of the activity. This can also give students a chance to practice their skills in a low-stakes way before beginning work on their final robot. Possibilities for this step include the following:
    • Build a moving mouth and customize it to make a practice pet.

    • Use the Hardware Components Quick Reference to describe the parts of the Hummingbird kit. Have students quickly prototype their planned animal in cardboard, placing pictures of the components where they want them to go.Robot Petting Zoo Components Reference
  3. Programming Exercises: You can use any language with Hummingbird support, but for beginners, we recommend Scratch (on computers or Chromebooks) or BirdBlox (on tablets).
  4. Planning: Have students sketch their animal and create a plan to build and program it. The Makeathon Design Notebook may be helpful. This is also a good time to show students how different mechanisms can be used with the Hummingbird motors; this playlist may be helpful.Robot Petting Zoo Makeathon Design Notebook
  5. Robot Making Time! Give students ample time to build and program their robots. This should be roughly half of the total makeathon time.
  6. Community Display: Open your robot petting zoo to inspire and delight your community! If you want, you can have visitors vote on fun categories like “Cutest Pet,” “Silliest Pet,” etc.
News

Physics of Pinball

The eighth graders of Vickery Creek Middle School demonstrate their knowledge of physics by creating pinball machines! They learn about simple and complex machines in physical science, and then they apply this knowledge in their STEAM elective.

This project starts with an introduction to how pinball illustrates Newton’s Laws of Motion. Roanoke Pinball Museum: Key Concepts is a helpful resource. Discovery: How It’s Made: Pinball Machine shows the construction of an actual pinball machine.

Next, students are challenged to build a pinball machine with the Hummingbird. The game must have a clear, engaging theme and incorporate at least 3 simple or compound machines to apply Newton’s laws of motion. Students can use the attached planning document to design their machine.

As students build their game, the DIY Cardboard Pinball Machine video may be helpful. In addition, this video shows how to use the Hummingbird servo to construct a basic flipper that uses a linkage. Students can experiment with modifying this linkage to get the movement that they want for their game. 

When students complete their games, invite the school community to come play!

Differentiation: Students ready for an additional challenge can add sound effects and score keeping through Scratch or Snap!.

Assessment: The rubric found in teacher materials can be used to evaluate projects.

News

Mood Ring Finch

A mood ring is a ring that changes color based on your body temperature. The idea behind the ring, which is explained in this video, is that your body temperature can be used to predict your mood. In this activity, you will use the Finch to predict mood in the same way!

Write a program that sets the color of the Finch’s beak based on temperature. The Finch should also tell you what your mood is for each color. The Finch should have at least three different moods, but you can add as many as you want!

To test the “mood Finch,” place your fingertip or palm over the temperature sensor.

News

Graphing with Finch

You have learned to use the Finch sensors to move a sprite on the screen. In this activity, you will use the commands on the Pen menu to graph the value of a sensor over time.

Start by writing a program that uses the block below to move the sprite on the screen. What numbers do you need to put in the blanks so that the sprite moves all the way to the top and the bottom of the screen

Now you want to record the path of the sprite on the screen. Explore the commands under the Pen menu. Start with the pen down block; you can think about this block as placing a pen on the “paper” of the screen. How can you change the color of the sprite’s path?

You have a program that tracks the value of the light sensor. To create a graph, you need to start with the sprite on the left side of the screen and gradually increase the x-coordinate as you change the y-coordinate. At the very beginning of your script, add a command that will make the sprite start at (-240, 0).

Within your loop, add a block that will increase the value of the x-coordinate by one pixel each time through the loop. When you run your program, you should see a graph that looks something like the one shown below.

Extension: Can you add axes to your graph? Can you graph the light value for exactly 30 seconds?

News

Mechanisms: Cable-Driven Robots

In this lesson, you will be building a cable-driven robot. Watch this video to see what it will look like.

The mechanism includes the following parts:

  • Links are connected by rotating joints.
  • A hollow guide is attached to each link.
  • A cable passes through all the guides. This cable is attached to a motor.

The motor pulls on the cable to move the links. As the motor pulls the cable, the guides become closer together, which makes the links rotate about the joints. Note that the cable can only move the mechanism in one direction, to bend the linkage at the joints.

Materials Needed

Paper Templates (See Teacher Materials)

When printing the templates, be sure to print them the actual size (no scaling) on 8.5” x 11” paper. You will use the templates to cut cardboard as shown in the instructions below. Be sure to use cardboard that is less than ⅛” thick.

  • Servo Unit
  • Box Unit
Other Materials
  • servo motor with bag of accessories
  • straws cut into 2” pieces (12 pieces)
  • yarn or cord
  • optional: Tapestry needle

Building a Cable-Driven Robot

  1. Use this video to assemble the servo motor unit.
  2. Attach the servo motor to your Hummingbird board and set it to 0°.
  3. Next, assemble the cable-driven mechanism using the video below. You may find it helpful to use a tapestry needle to thread the cable through the straws.
  4. Reattach the servo to the Hummingbird board. Gradually increase the angle of the servo and observe the movement of the links.
  5. Continue to increase the servo angle until the links stop moving. This is the maximum angle that you should use with your mechanism. Record this angle.
  6. Write a program to move the servo back and forth between 0° and the maximum angle.
  7. The motor acts to bend the linkage. What provides the energy to straighten the linkage? How could you use another servo to straighten the linkage?
  8. We used a cable-driven mechanism to create this giraffe. What are some other ways that you might use this mechanism in a robot?

How the Mechanism Operates

You can use geometry to investigate how moving the cable causes the cable-driven linkage to bend at the joints.

  1. The diagram below shows one joint of the cable-driven robot. We can approximate this as the triangle JAB. Assuming that the joint is midway between the two guides, what type of triangle is JAB?
  2. Use your mechanism to measure the length of line segments JA and JB. Do these measurements support your answer to (1)? Explain.
  3. Angle AJB in the diagram measures 110°. Draw a scaled version of triangle JAB using the measurements that you have taken so far and this angle. Lengths in the scaled version should be 10 times larger than the real-world lengths.
  4. Measure the scaled length of line segment AB. What real-world length does this correspond to?
  5. When the motor pulls on the cable, it acts to shorten the line segment AB. Suppose that the length of AB decreases by 20%. What is the new scaled length of this line segment?
  6. Construct a new scaled version of triangle JAB using the decreased length. Measure angle AJB.
  7. How has the change in cable length affected angle AJB? Explain what this means for a cable-driven robot.

Using Two Linkages

You can create a cable-driven robot with multiple linkages. In this part of the lesson, you will connect two linkages to your servo motor unit. Examples with even more linkages are shown below.

  1. Make sure your servo motor is set to 0°.
  2. Use this video to modify your cable-driven mechanism to include two linkages. You will need a second cardboard box as a spacer. You may have one from a previous lesson, or you can make a second box using the instructions and paper template above. Alternatively, you can team up with a neighbor for this section!
  3. Reattach the servo to the Hummingbird board. Gradually increase the angle of the servo and observe the movement of the links.
  4. Continue to increase the servo angle until the links stop moving. This is the maximum angle that you should use with your mechanism. Record this angle.
  5. Write a program to move the servo back and forth between 0° and the maximum angle.
  6. Compare your two-linkage mechanism to the version with a single linkage. Do the two linkages move symmetrically? Why or why not?
  7. We used two cable-driven linkages to create this bird. What are some other ways that you might use this mechanism in a robot?

Creating Cable-Driven Robots

You have already seen the giraffe and bird examples, but the you can create many other cable-driven robots! This video shows a cable-driven robotic hand.

In this lesson, the linkages were created from cardboard, but you can use other materials. This blooming flower was created with stiffened felt.

Now it is time to create your own cable-driven robot! How many linkages will you need? Will you connect them to the same servo or to different servos?

Finding More Information

News

Mechanisms: Gear Trains

In this lesson, you will be building mechanisms with gears. Watch this video to see an example.

A gear train is a mechanism that consists of two or more gears. Gears are disks with teeth that mesh together. The diagram below shows a gear train with two gears. This mechanism has the following parts:

  • The drive gear is rotated by a motor.
  • The teeth of the drive gear mesh with those of the driven gear.

As the drive gear rotates, its teeth turn the driven gear. How fast the driven gear rotates depends on the number of teeth it has relative to the number of teeth of the drive gear.

Materials Needed

Paper Templates (See Teacher Materials)

When printing the templates, be sure to print them the actual size (no scaling) on 8.5” x 11” paper. You will use the templates to cut cardboard as shown in the instructions below. Be sure to use cardboard that is less than ⅛” thick.

  • Motor Unit
  • Box Unit

Other Materials

Building the Gear Train Mechanism
  • Gear motor plus plastic brick adapter
  • Pipe cleaner
  • 3 Technic friction axle pegs
  • 1 Technic 13M beam
  • 2 Technic gears with 40 teeth
  • 1 3M Technic axle
  • 1 Technic bushing
Additional Materials for Investigating the Gear Ratio
  • Pipe cleaner
  • 1 Technic gear with 24 teeth
  • 1 Technic gear with 8 teeth
  • Stopwatch
Additional Materials for Extending the Gear Train
  • More axles, bushings, and gears

Building the Gear Train Mechanism

  1. You will need a motor unit for this lesson. You may have already built one. If not, you can use these instructions to assemble the motor unit.
  2. Next, use this video to assemble your gear train mechanism.
  3. Attach the motor to motor port 1 on your Hummingbird board. Write a simple program to turn on the motor. Observe the movement of the gears.
  4. Does the drive gear rotate clockwise or counterclockwise? Does the driven gear rotate clockwise or counterclockwise?

Investigating the Gear Ratio

  1. Glue a small piece of pipe cleaner to the bushing, as shown in the picture below.
  2. Set the motor speed to 40 and measure the amount of time that it takes the driven gear to make ten rotations.
    1. Start the stopwatch when the pipe cleaner passes the black beam.
    2. Stop the stopwatch when the pipe cleaner has made ten complete rotations. The pipe cleaner should be in the same position that it was when you started the stopwatch.
    3. Enter your measurement in the table below and compute the time required for one rotation of the driven gear.
  3. What is the time required for one rotation of the drive gear? Explain your answer.
  4. Replace the driven gear with a gear with 24 teeth. This video will show you how. Make sure that the teeth of the drive gear mesh with the teeth of the new driven gear.
  5. Set the motor speed to 40 and measure the amount of time that it takes the driven gear to make ten rotations.
    1. Enter your measurement in the table and compute the time required for one rotation of the driven gear.
  6. Replace the driven gear with a gear with eight teeth. Make sure that the teeth of the drive gear mesh with the teeth of the new driven gear.
  7. Set the motor speed to 40 and measure the amount of time that it takes the driven gear to make ten rotations.
    1. Enter your measurement in the table and compute the time required for one rotation of the driven gear.
  8. The gear ratio is defined as the proportion that relates the number of teeth on the driven gear to the number of teeth on the drive gear.
    1. Compute gear ratio for each driven gear and enter it in the table.
  9. Based on your data, write an equation that predicts the time for one rotation of the driven gear based on the gear ratio and the time for one rotation of the drive gear. You should be able to defend your equation.

Extending the Gear Train

A gear train can include more than two gears. Gears in between the drive gear and the driven gear are called passive gears. For example, the picture below shows a gear train with three gears. The 24-tooth gear in the middle is a passive gear.

Try building different gear trains. How does the number of gears in the train influence the direction of rotation of the driven gear?

In this lesson, the gear ratio was always greater than or equal to 1. However, this is not a requirement. Try using a smaller gear as the drive gear!

Using Gears to Create Robots

Gears are used in a robot design to increase or decrease the speed of a motor. Increasing the speed of the motor decreases the torque that it can apply; this means that the motor cannot apply as much force to rotate an object. Decreasing the rotation speed of the motor increases the amount of torque that it can apply. If you need your robot to rotate something heavy, you will need to use gears to decrease the rotation speed.

Gear trains are often used to in vehicles; for example, this video shows how gears are used in a car. However, gears can also be used in many other ways. The video below shows how gears were used to create a robotic Etch-A-Sketch and ballerinas that rotate at different speeds.

Now it is time to use gears to create your own robot! Do you want to increase or decrease the rotation speed of the motor? How many gears do you need in your gear train?

Finding More Information

News

Mechanisms: Linkages

In the last two lessons, you learned to make mechanisms with cranks, rods, and pistons. These mechanisms are special cases of a more general type of mechanism called a linkage. In this lesson, you will explore other types of linkages. Watch this video for an example.

The diagram below shows a four-bar linkage. This mechanism has the following parts:

  • Four links that are connected by four rotating joints.
  • Three of the links can move, but the fourth is fixed in position. This link is called the ground link.
  • One of the moving links is a crank that is rotated by a motor.

As the crank rotates, it causes two other links to move while the ground link remains fixed in position. Varying the lengths of the links produces different patterns of movement.

Materials Needed

Paper Templates (See Teacher Materials)

When printing the templates, be sure to print them the actual size (no scaling) on 8.5” x 11” paper. You will use the templates to cut cardboard as shown in the instructions below. Be sure to use cardboard that is less than ⅛” thick.

  • Motor Unit
  • Box Unit
Other Materials
Building the Four-Bar Linkage Mechanism
  • motor unit with gear motor plus plastic brick adapter
  • pipe cleaner
  • 5 Technic friction axle pegs
  • 4 Technic beams, two 5M and two 13M
Additional Materials for Exploring More Complex Linkages
  • 11 Technic friction pegs
  • 4 Technic 13M beams
  • 2 Technic 5M beams
  • 2 Technic 3M beams
  • 1 Technic 9M beam
  • motor unit with gear motor and plastic brick adapter
  • small box
  • pipe cleaner
  • marker

Building the Four-Bar Linkage Mechanism

  1. You should complete the crank lesson prior to this one. If you have not already completed the crank lesson, do that first. This lesson will use the motor unit from the crank lesson.
  2. Next, use this video to assemble your linkage mechanism.
  3. Attach the motor to motor port 1 on your Hummingbird board. Write a simple program to turn on the motor. Observe the movement of the four-bar linkage.

Grashof Condition

Not every set of link lengths will produce a working four-bar linkage. The lengths must satisfy an equation known as the Grashof condition. This equation is defined in terms of the following variables:

  • s is the length of the shortest link
  • l is the length of the longest link
  • p is the length of one of the intermediate links
  • q is the length of the other intermediate link

  1. Measure the lengths of all four of the links in your mechanism (including the ground link). Which links are s and l?
  2. You have seen that your linkage can move, so you know that it should satisfy the Grashof condition. Use your measurements to show that it does.
  3. Next, move the pin that connects the two 13M beams. Place this pin so that it is in the center hole for both of these beams. You may have to rotate the crank to reconnect the two beams.
  4. How have the link lengths changed for your mechanism? Does the linkage still meet the Grashof condition? Predict whether or not the linkage will be able to move.
  5. Turn on the motor. Can the linkage move? Does this support or contradict your prediction?
  6. Again, move the pin that connects the two 13M beams. Place this pin so that it is in at the end of one beam and in the fifth hole of the other (close to the joint of the ground link). You may have to rotate the crank to reconnect the two beams.
  7. How have the link lengths changed for your mechanism? Does the linkage still meet the Grashof condition? Predict whether or not the linkage will be able to move.
  8. Turn on the motor. Can the linkage move? Does this support or contradict your prediction?

Building a Scissor Linkage

  1. Use this video to transform your four-bar linkage into a scissor linkage. You will need four more 13M beams and six more connecting pins.
  2. This mechanism is based on a four-bar linkage, but it uses additional links to increase the amount of movement produced by the linkage.
  3. The picture below shows a scissor linkage at two different positions.
    1. As the red point on the linkage moves from height h1 to height h2, how far does the top of the linkage move? Defend your answer using congruent triangles.
    2. Based on your answer, what is the advantage of a scissor linkage? Can you think of any disadvantages?
  4. We used the scissor linkage to animate a fish leaping out of the water. What are some other ways that you might use a scissor linkage in a robot?

Exploring More Complex Linkages

  1. For the next part of this lesson, you will need two motor units. You can use these instructions to assemble a second one, or you can team up with a neighbor!
  2. Use the two motor units to create a new linkage for drawing. You will need a small box, a pipe cleaner, paper, a marker, two 5 M beams, two 13 M beams, two 3M beams, one 9M beam, and 11 connecting pins.
  3. Attach the motors to motor ports 1 and 2 on your Hummingbird board. Write a program to turn on the motors. What does your robot draw?
  4. Vary the speeds of the motor. Use a different piece of paper for each speed combination and label it with the speeds you used. This will enable you to compare your drawings more easily.
  5. How do the speeds of the two motors affect what your robot draws?
  6. What does the robot draw when the two speeds are equal? How is this different from the drawings when the speeds are different?
  7. Your drawing robot is a five-bar linkage. Draw a picture of it and label the five links (don’t forget the ground link!).
  8. A five-bar linkage can move in more different ways than a four-bar linkage. That is why you can use two cranks to make two of the links rotate independently. What would happen if you tried to attach motors to two of the links in the four-bar linkage?

Using Linkages to Create Robots

In this lesson, you have used different kinds of linkages to create several different robots, but there are so many more possibilities! Theo Jansen even uses linkages to create enormous works of art!

As examples, this video shows a linkage that was used to make the wings of a penguin flap, and the video below shows a robot arm that incorporates a number of linkages. How would you describe the linkages shown in these videos?

Now it is time to use linkages to create your own robot! How can you modify the linkages you used in this lesson to make something new?

Finding More Information