Introduction: Introduction

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The following information is a single lesson in a larger project. Find more great projects here.

Project Overview:

Get control of other devices around you by pressing their buttons with Arduino! This project takes advantage of a special switch called an optocoupler which lets you operate one circuit with another. This can be used for hacking an existing device, and it's good to start with something simple, like a flashlight.

Step 1: A Few Words Before We Start...

Warning! You’re no longer a beginner if you are doing this project. You’ll be opening up an electronic device and modifying it. You’ll void your device’s warranty, and if you’re not careful, you might damage the device. Make sure you’re familiar with all the electronics concepts in the earlier projects before you attempt this one. We recommend using inexpensive items you don’t mind damaging for your first few projects, until you develop experience and confidence!

We'll also provide a flashlight prototype in the Workplane to "hack" so you can learn how the rest of the project works. Now let's get started!

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Step 2: Project Description

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While the Arduino can control a lot of things, sometimes it’s easier to use tools that are created for specific purposes. Perhaps you want to control a television or a music player, or drive a remote control car. Most electronic devices have a control panel with buttons, and many of those buttons can be hacked so that you can “press” them with an Arduino.

Recording and playing back sound on a digital sound recorder would be a good example! We will hack buttons using anoptocoupler.

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Step 3: Bill of Materials

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You will need the following electrical components for this project:

1 220 ohm resistor

1 optocoupler

...and of course your Arduino Uno and a breadboard!

If you are going to hack your own electronic device, find something simple and inexpensive to start out, like a flashlight. Or you can build a prototype flashlight on another breadboard.

  1. Locate the resistor and optocoupler in the picture above.

  2. While it's possible to hack buttons without soldering, it certainly does make it easier. For more information you can look at arduino.cc/soldering.

  3. Continue to the next step.

Step 4: Optocouplers

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Optocouplers are integrated circuits that allow you to control one circuit from a different one without any electrical connection between the two.

  1. Inside an optocoupler is an LED and a light detector.

  2. When the LED in the optocoupler is turned on by your Arduino, the light detector closes a switch internally.

  3. The switch is connected to two of the output pins (4 and 5) of the optocoupler. When the internal switch is closed, the two output pins are connected. When the switch is open, they’re not connected. This way, it’s possible to close switches on other devices without connecting them to your Arduino.

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Step 5: Circuit Diagram

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The circuit diagram below shows that the project is actually quite simple. The optocoupler is connected to digital pin 2 like a simple output. When pin 2 is LOW, the optocoupler is off. When pin 2 is HIGH, the internal LED comes on - in turn, it activates your hacked button on the external device.

  1. Continue to the next lesson to learn how to set up the circuit.

Next Lesson:Setting Up the Circuit

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