Build 009Queued

A switch with no moving parts

Replace the relay's click with a transistor and use a tiny signal to control a brighter light.

Blueprint illustration of a transistor switching an LED on a breadboard

Before we start

The relay uses a moving piece of metal to switch a circuit. Can a solid piece of material do the same job?

The goal

Use a transistor as a switch, and nothing more complicated yet.

How we'll do it

  1. 01Identify the transistor's three pins using its diagram.
  2. 02Build the LED path through the transistor with a current-limiting resistor.
  3. 03Use the button and a second resistor to send a small signal to the control pin.
  4. 04Compare the silent electronic switch with the relay we could see and hear.

Read alongside

Family read

The Manga Guide to Electricity

Kazuhiro Fujitaki and Matsuda

For older readers. A comic that goes from everyday circuits to semiconductors and transistors.

Bench guide

Electronics for Kids

Øyvind Nydal Dahl

Projects that show how a transistor controls current.

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