Invention Literacy Foundations: Invent an Alarm Challenge!

With our new plug and play alarm app, you can spend more time inventing your physical alarm trap since we took care of the coding on this one! Up until now you've learned how circuits work and explored Makey Makey. But let's go further by exploring the switch concept. Switches are a simple type of sensor. Sensors and microcontrollers power our world. But what is a sensor? And what is a microcontroller? And how do they work together? Let's get started! And invent a sensor to trigger an alarm!

Sound the Alarm!

 trigger when closed

Today you are going to invent an alarm system! To do this, you will build a sensor that activates our alarm app. When you connect a sensor to a Makey Makey, you can detect specific types of information and adjust what you want the output to be with the code that you create. For this project, we did the coding and created an alarm, but you get to decide how the alarm will work.

Momentary Switch Doorbell or Door Alarm

Before we invent our own alarm system, let's create some simple switches first! 

Vocabulary: A switch is a component that requires a physical action to close a circuit. Just like the keys on your keyboard! A Switch can be momentary or maintained.

Let’s make a momentary switch first. This means the switch will only be “on” as long as the switch is actuated. Normally a switch is an open circuit until it is actuated. Meaning the circuit is open until you push the switch to activate it. Just like a keyboard button, or a calculator button. 

You can also easily make a maintained switch with office supplies. A maintained switch remains on once you turn it on or off once you turn it off. Just like a light switch in your house.

The best way to learn about switches to make a few different types.

First let's build a doorbell with paperclips and brass fasteners! 

Put two brass fasteners through a small piece of cardboard. Place a paper clip on one fastener, and bend it so it doesn't touch the other fastener. Clip SPACE to paper clip fastener and EARTH to the other. When you press the paper clip to the second fastener, you close the loop and complete the circuit. This switch most resembles a keyboard key or a morse code machine!

Plugged into our alarm app, this will sound the alarm that the doorbell has been triggered!

What other type of trigger could you build that would be actuated when someone presses on or steps on something? And what purpose will your alarm serve?

Brainstorming and Testing Alarm Systems

Design considerations:

  • Your first design consideration is to think about where you want to place your momentary alarm.

  • How will you place two conductive items so that some movement triggers your alarm? 

  • What items will you use in crafting your alarm system? What items work well?

  • How can you ensure the alarm is triggered without bringing the system crashing down? 

In this video below, you can see how you could wire up your momentary push button as a doorbell outside your door. I used a phone with an adapter so I could leave the Makey Makey behind the door. To transform the doorbell into an alarm, I used a wire coat hanger (make sure you sand off coating to expose the metal if you use a coat hanger) hung it above a door and connected the coat hanger to the "Up arrow" on Makey Makey. On the door, I placed a strip of HVAC tape connected to "EARTH" on the Makey Makey. This alarm is triggered when someone opens the door as the coat hanger closes the circuit when it touches the aluminum foil strip. Also, the coat hanger is held with a binder clip to allow for movement! (Make sure to ask your parents before using any thumbtacks or applying tape to walls or doors in your room! )


Maintained Switch Alarm

What if you want an alarm that is always set and will blast when someone opens the box that holds your precious goods?

GIF from this Scratch Project

You can make a simple maintained switch by clipping EARTH to one binder clip and SPACE to another. When the two binder clips touch, the circuit is closed and complete! When you separate the binder clips, the circuit is open once again.

Get more cool ideas like this from Scrappy Circuits! You can use these same switches to light up LEDS. Plus, the folks at Scrappy Circuits have even more cool ideas for building switches out of scrappy everyday stuff!

This switch is more like a light switch (which is a toggle switch) it comes on when you flip it and off when you turn the switch to "off." That means a light switch works by closing a circuit to turn on the light when you flip the switch one way, and turns it off (opens the circuit) when you flip the switch the other way.

Design considerations:

  • Your first design consideration is to think about what you want to protect and what container you will use to create your "toy box alarm!"

  • How will you place two conductive items so that they are always touching unless someone is trying to access what your alarm is protecting?

  • What items will you use in crafting your alarm system? What items will work well and can be secured to a box, lid, etc.?

  • How can you ensure the alarm is set and no one can see the wires or Makey Makey?

 Always set alarm


Time Investment
30 min
2nd- 12th 


  • Makey Makey
  • Foil
  • Cardboard


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