Make an Adaptive Switch

Summary

Areas of Science

Electricity & Electronics
Human Biology & Health

Difficulty

Method

Engineering Design Process

Time Required

Short (2-5 days)

Prerequisites

None

Material Availability

This project requires a programmable board like an Arduino, Raspberry Pi, or micro:bit.

Cost

Low ($20 - $50)

Safety

No issues

Credits

Ben Finio, PhD, Science Buddies

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.

https://www.youtube.com/watch?v=m_K0zZHPrBs

Abstract

How could you send a text message without using your thumbs? What about typing on a keyboard or using a video game controller without using your fingers? Due to a variety of medical conditions like cerebral palsy or paralysis from an accident, some people might be unable to easily use their hands and fingers to push small buttons or use joysticks. However, they might be able to use their entire hand to push a single larger button or use another part of their body like their foot or even their head. Adaptive switches are designed to make it easier for these people to interact with devices like toys (Figure 1), computers, and electric wheelchairs.  

Image Credit: OLI8970 / Creative Commons Attribution-Share Alike 4.0 International

Figure 1. A toy with two external adaptive switches that make it easier for some users to interact with.

Internally, a basic switch or button just consists of two conductive electrical contacts. When these contacts are not touching each other, they form an open circuit. When they touch each other, they form a closed circuit. You can make a basic electrical switch using conductive materials you have around the house, like aluminum foil. A programmable microcontroller like an Arduino or micro:bit or, a computer with accessible input/output (I/O) pins like a Raspberry Pi, can detect whether a switch is open or closed. You can then program the board so the switch activates a certain output - like lighting up LEDs (Figure 2), playing sounds on a speaker or buzzer, moving a motor, or sending a message. 

Image Credit: Ben Finio / Science Buddies

Figure 2. Demonstration of a basic electrical switch with a micro:bit board. There are two pieces of aluminum foil connected to two different I/O pins with alligator clips. When the pieces touch, the micro:bit detects the closed circuit, and displays a smiley face with LEDs.

For an engineering project, can you design and build one or more accessible switches that trigger certain outputs? Here are some things to consider:

• Who is your intended user for the switch? What movements or body parts can they use to press it? What do they need to control?
• You will need to decide if your switch is "normally open," meaning the electrical contacts are normally not touching each other, and they only touch when you activate the switch, or "normally closed," meaning the opposite. 
• You will need to decide whether to build a "toggle" switch that holds its position after you activate it (like a light switch on the wall), or a "momentary" switch that springs back to its original position when you release it (like a key on a keyboard).
• You will need to learn how to interface a button or switch with a programmable board of your choice. You can find related tutorials and projects here:
  • Arduino tutorial about momentary button
  • Arduino tutorial about toggle switch
  • Project for connecting an external switch to a micro:bit
  • Project for connecting external switches to a Raspberry Pi

Figures 3, 4, and 5 show an example of a normally open, momentary foot pedal switch. The switch consists of two pieces of cardboard attached together with a hinge made from duct tape. Each piece of cardboard has a piece of aluminum foil taped to it. Since the cardboard is an insulator, normally there is no electrical contact between the pieces of aluminum foil, meaning the switch is normally open. When you press down on the top piece of cardboard, the two pieces of aluminum foil touch each other and the switch closes. When you release the switch, the rubber bands pull it back to its original position, making it a momentary switch as opposed to a toggle switch.

Image Credit: Ben Finio / Science Buddies

Figure 3. Front view of the cardboard foot pedal.

Image Credit: Ben Finio / Science Buddies

Figure 4. Rear view of the cardboard foot pedal.

Image Credit: Ben Finio / Science Buddies

Figure 5. Pressing down on the cardboard foot pedal.

Figures 6 and 7 show another example of a normally open momentary switch. This one resembles a large button made from two slightly bent pieces of paper, taped together at the edges, with two pieces of aluminum foil taped to the insides. Normally the sheets of paper curve apart slightly so there is a gap between the pieces of aluminum foil. This gap closes when you press down on the paper, and opens when you let go and the paper springs back into its slightly curved shape.

Image Credit: Ben Finio / Science Buddies

Figure 6. Top view of the paper adaptive switch.

Image Credit: Ben Finio / Science Buddies

Figure 7. Inside view of the paper adaptive switch with the aluminum foil visible. 

These two examples show how you can build switches with the same electrical functionality but totally different physical designs. What kind of switch can you build for your project?

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Global Goals

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Reduced Inequalities: Reduce inequality within and among countries.

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