Designing and Crafting Alarm Systems

30-60 min

Ages 8+

What Will You Make?

You will learn to code an alarm that will sound when you press the paperclip to the brass fastener.

Note: This is a project for students who’ve finished the Beginner Level Makey Makey class or makers who already have basic knowledge about Makey Makey.

You may want to try these projects first:

This project also uses elements from:

Crafting and Designing Switches

What Will You Learn?

You’ll learn to code alarms with the Makey Makey, and be challenged to design your own alarm system.

Coding an Alarm System- Momentary Switch

Step 1

Grab your paper clip push button switch, and let’s learn how to code it in Scratch!

Step 2

You need to code an alarm that will sound when you press the paperclip to the brass fastener. It isn’t too difficult, but you will need a quick trick to make sure the alarm only sounds when you complete the circuit!

To trigger your alarm sound, it’s really pretty easy to code! You need an if/else statement nestled into a forever loop that will sound the alarm when the up arrow is pressed. Otherwise, you want the alarm sound to stop.

Step 3

Since this code is in s forever-loop that reads from the top down, this is how Scratch is running the code:

Check to see if up arrow is pressed
If yes: play sound until it’s done
Go through the loop again
If no: (Or if up arrow isn’t pressed anymore) trigger code for else: to stop all sounds

This if/else statement works great for changing costumes, broadcasting messages, etc. However, it is trickier with sound as the code will never get to the else statement while the sound is playing, so if you want to stop the sound as soon as key is not pressed, you’ll have to add another script.

Step 4

You need the reporting block “Not” from the Operator Palette. This code will be under a separate “When Flag Clicked” so that it will always be running and checking to see “if the up arrow is not pressed.

Check to see if up arrow is not pressed
If it is not pressed, stop all sounds in the project.

Now your code will only be triggered when the circuit is closed. If the two conductive touch points do not touch then the alarm will be silenced!

And that’s really all you need to code for your alarm! You might want to add more effects, so check out this coding video walkthrough of using your momentary push button alarm from the first project in this series. Follow along to code your own Scratch project. Then design your own push-button alarm!

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! )