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Invent a Security Device

by erin_littleBits

Published on March 8, 2016

Students will use the littleBits Invention Cycle, and an understanding of the basics of circuitry and environmental sensors to construct a backpack alarm that protects students’ belongings. Students will then modify their alarms to make them function for different users and environments. Conclude the activity by having students create 30-second commercials to pitch their product.

By the end of the Lesson, students will be able to:
  • Create and test a circuit containing a power source, inputs and outputs
  • Construct a prototype of a security device using littleBits and other materials
  • Test their prototypes and make improvements
  • Self-assess their work based on the outlined success criteria and constraints
  • Demonstrate their ability to Create, Play, Remix and Share an invention through the littleBits Invention Cycle by recording their processes in the Invention Log
  • Summarize their process and share the resulting invention by creating commercials to pitch their product.

The Invention Log checklist (Invention Log pg. 18) can be used to assess your students’ understanding of the Invention Cycle, use of the Invention Log and ability to attain the objectives of the lesson. For formative assessment while students work, you can use this checklist to ask questions about their current task and ensure that they are on the right track. The checklist can also be used as a self-assessment tool by students as they move from phase to phase. For summative assessment, you can use this checklist to review students’ entries into their Invention Log and assess their understanding of the challenge and the invention process as a whole.


3-5-ETS1-3 Engineering Design: Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
  • To fulfill this standard. students are explicit about the need or want being designed for, and call it such, as well as criteria for success and constraints of materials, time, cost etc. that they’re willing to work within.

MS-ETS1-3 Engineering Design: Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solutions to better meet the criteria for success.
  • To fulfill this standard. students test their prototypes and make improvements. Set all but one variable as fixed, and change just one parameter in attempts to maximize the agreed upon criterion for success. Students may also be allowed to “borrow” the best aspects from one another’s designs during this process.

To meet these standards, students will need to fill out information in the Remix section of the Invention Log (pg. 11 and 12) every time a variable is changed and tested. Be sure to print additional copies of these pages before the lesson begins.

*For other curricular connections, see the “Extension” section at the end of this lesson.

littleBits Invention Log
Guided projects can pair with the Invention Log for the Play and Remix Phases of the Invention Cycle. The Create phase has already been outlined for students in their Invention Guides.


Hearing beware: When run as a group exercise, this activity can get quite noisy! You may want your class to use light Bits in lieu of the buzzer for some of the Play and Remix prompts.

The light sensor can be a tricky Bit. Use the purple screwdriver to turn the sensitivity dial counterclockwise until the desired amount of output is activated. Depending on the abilities of your students, you may want to demonstrate the sensitivity adjustments on the light sensor before diving into the Create and Play phases.

power, output, input, magnetism, criteria for success, circuits, constraints


Duration: 90 minutes (minimum) *For tips on how to break up your lesson over multiple class periods, see pg. 117 of the STEAM Student Set Teacher’s Guide

Lesson Guide


This lesson can be done individually or in small groups (2- 3 students). Each group will need at least one STEAM Student Set and Invention Guide, plus one Invention Log and Assessment Checklist per student. We suggest handing out the Bits in the Create phase to keep students focused on initial instructions and review activities. For more experienced users, you may want to provide access to additional Bits in the Play and Remix phases to provide a greater diversity of circuit combinations. If students don’t have their own backpacks, hand out an opaque box with a lid to each group.

During the Create phase, students will construct their first prototypes according to instructions in the Invention Guide. You may want to construct your own example prototype before the lesson begins. Seeing a working model of what they are building can help the students understand the goal of their Create phase and will allow you to quickly demonstrate it working in the Play phase.


Begin the activity by leading a short review of key vocabulary (see above) and the littleBits basics (e.g. magnetism, order matters, color-coding). If this is the first time your students will be engaging in a challenge using the Invention Cycle framework and the Invention Log, take 5- 10 minutes to review each stage (pg. 11).

Introduce the lesson objectives and define criteria for success and constraints that are appropriate for your students. For example, your criteria for success could be creating a security device that is hidden from view (so potential snoopers can’t see it!). A constraint could be that the circuit must contain power, input and output. While the first prototype will be guided, your students will be able to customize their throwing arms in the Remix phase of the Invention Cycle.

STEP 3 : CREATE (20–30 MIN)

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Picture 1

A. CREATE IDEAS: Engage your students in a discussion about why and how we use alarms. Write a list of responses on the board. •Where do we encounter alarms? •What types of alarms are there? I.e. lights, sound •How are they triggered? •What is their purpose? Students will be able to test out some of these ideas in the Remix phase.

B. CREATE PROTOTYPE: Students will follow the instructions in their Invention Guide to build their first prototypes of the security device. Encourage students to reference the Bit Index (pg. 7- 27 in their Invention Guides) if they get stuck or want to learn more about a particular Bit or accessory. For younger students, you may want to pause the class after each step to troubleshoot any common problems, as well as Share successful build strategies amongst the groups.

STEP 4 : PLAY (10–15 MIN)

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As you move through the Play prompts, be sure to have students record their PLAY process and reflections in the Invention Log (starting with "How did your testing go?")

How did your testing go? Once the prototypes have been constructed, students should test their alarms to make sure they work and to explore the circuit functionality.

A. TEST THE CIRCUIT (STUDENT PROMPTS): Students should try using their alarms in their backpack, a box, or drawer. When the alarm is in a dark space, the buzzer should be silent. When you open the container to let in light, the buzzer should sound the alarm. •Some containers might not be sufficiently dark inside. If the alarm sounds even when closed in the box/bag/drawer, try turning the sensitivity dial on the light sensor down (counter-clockwise) a little. You should also check to make sure the light sensor is in light mode. •If your alarm doesn’t sound at all, make sure the sensitivity dial is turned all the way up, the power Bit is on (red light should shine), and that there is enough charge in the battery.

B. HOW IT WORKS: Either as a class or in groups, ask students to discuss/explain how the circuit works. A clear understanding of how it works will help them explore and experiment during the Remix phase. Make sure students understand how each component in the circuit functions, paying close attention the light sensor. Note: your students will have access to the answers above in their Invention Guide. Demonstrating how the circuit works and asking probing questions will help assess their understanding of the material.

For example, you could ask: What happens when... •You turn the sensitivity of the sensor all the way clockwise? (high sensitivity) •You turn the pulse all the way counterclockwise? (the buzzer will sound very slowly - if triggered by the light sensor) •The power Bit isn’t shining red (the switch isn’t moved to the on position; the alarm doesn’t move; troubleshooting: the battery and cable aren’t connected)

Be sure to have students record their notes and processes in the Invention Log.

STEP 5 : REMIX (20–30 MIN)

To meet the outlined NGSS standards, instruct students to fill out a new REMIX section in their Invention Logs (pg. 11 and 12) every time a variable is changed and tested. If you are do not plan to adhere to the NGSS standards, allow students more flexibility and exploratory pathways during this phase of the design process.

PROTOTYPE # 2 (AND MORE...): Now it’s time to put your students’ Engineering Design skills to work to customize their security device. Remixes A, B and C (Invention Guide p. 58) will walk your students through possible adjustments. You may also choose to extend the lesson to meet additional curricular requirements (be sure to check out the Extension section for more ideas). You can find more advice on how to conduct the Remix Phase in the Invention Advisor section (pg. 36). As students make changes to their inventions, make sure they are documenting how their prototypes are changing and the results (good and bad) in their Invention Logs.


Change the Bits’ settings: •How could the alarm work in the opposite setting, triggering when it’s dark? •Switch the light sensor mode to “dark” mode. If the alarm doesn’t sound reliability, try adjusting the sensitivity of the light sensor. •Adjust the speed of the pulse Bit to change how fast the alarm sounds. •In your opinion, what setting would make the best alarm?

Switch it up - Try using your alarm in different places/scenarios: •Try the alarm in a desk drawer, locker or under the backpack. •Put it on the windowsill and test it as a wake-up alarm. •Use the alarm as a prank when someone turns out the light.

Mix it up - Swap out a Bit or add materials: •How can different materials or Bits Create a bigger impact? •Add a DC motor and attach a sign with a message or scary monster on it. •How could the sound be amplified? •Wrap a paper cup or cone around the speaker. •How could the alarm be adjusted for someone with hearing disabilities? •Add lights or a sign.

REMIX TIPS •As you walk around the room, ask students to explain their Remix choices and the resulting change in functionality and outcomes. •NGSS-3-5ETS1-3 and MS-ETS1-3 Connection: Allow students to “borrow” the best aspects from one another’s designs, setting all but one variable as fixed, and changing the amount of just one parameter to see how to maximize the agreed- upon criterion for success.

STEP 6 : SHARE (20–25 MIN)

Share your students’ unique security devices by having them create 30-second commercials (to “sell” their product). Be sure the device has a name, a price, an intended user and a story around how the alarm can be used.


At the end of the lesson, students should put away the Bits according to the diagram on the back of the Invention Guide, clean up their materials and hand in their Invention Logs.


Incorporate one (or more!) of the following extensions in the Remix section of this challenge to bolster your lesson’s NGSS applications:

3-5-ETS1-1 Engineering Design: Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

•To fulfill this standard. allow students to come up with an agreed upon criterion for success of their launcher (everyone should have the same goal) and constraints on them, e.g. “cost” of materials or “weight” in terms of number of pieces. An imagined, but motivating, scenario could be provided. They should record these criteria and constraints in the criteria and constraints section of their Invention Logs.

3-5-ETS1-2 Engineering Design: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.

•To fulfill this standard. allow students to come up with different solutions to a problem and explicitly compare them on the based on their ability to meet the goal within constraints.

MS-PS4-2 Waves and their applications in technologies for information transfer: Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

•To fulfill this standard. use the buzzer to explore how sound waves work. Supplement with a sound level meter. Support students in developing a model for how sound works. Why is it so faint if the light is turned on inside the backpack, but loud if the light reaches the sensor by opening the backpack?

MS-ETS1-2 Engineering Design: Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that many limit possible solutions.

•To fulfill this standard. allow students to come up with different solutions to the problem and explicitly compare them on the basis of their ability to meet the goal within the constraints.