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MONKEY COUCH GUARDIAN

Use an Arduino to build this stalwart defender of upholstery!

When MAKE’s editor-in-chief Mark Frauenfelder wanted a gadget to chase his pesky pets off his favorite couch, he programmed an Arduino microcontroller to read a motion sensor and activate a motor in response — in this case, the motor of an old-fashioned cymbal-banging toy monkey. Take that, cat!

The Monkey Couch Guardian is a great project for getting started with microcontrollers, the tiny computers you can use to control everything from home heating systems to robots.

Since we first published this Weekend Project, it has entertained thousands on YouTube, Boing Boing, Virgin America, and at Maker Faire. Make yours this weekend!

Here’s how it works.

1. Program the Arduino. Download the free Monkey Couch Guardian code from the project page, then open it in the Arduino development software (also free) and upload it to the microcontroller. Simple. The code tells the microcontroller to listen to the motion sensor, and then switch on the monkey when something moves!

2. Hack the monkey. Tap into the monkey’s battery power supply, and add wires to connect a relay that’ll bypass the monkey’s switch.

3. Connect a relay. On a breadboard, connect the relay’s switch to the monkey’s power and ground, and connect the relay’s coil to the Arduino’s ground and digital I/O pin 13, which you’ll use as an output.

4. Connect a motion sensor. It’s powered by the Arduino; just connect the PIR sensor to the Arduino’s 5V power, ground, and for the sensor’s signal, digital I/O pin 12, which you’ll use as an input.

Get along, doggie! This monkey detects intruders up to 20 feet away.

5. Make an enclosure. We like cigar boxes and RadioShack project boxes. Put the sensor on the front, the monkey on top, and the electronics inside. You can power the Arduino from a wall AC adapter or an optional 9V DC battery pack. Bonus: Connect an optional toggle switch and LED power indicator, so you know when your monkey is on watch.

6. On guard! When the Monkey Couch Guardian is switched on, any motion within about 20 feet will trigger the PIR sensor. The monkey will start shrieking and clanging his cymbals, scaring away any unwanted intruders, furry or otherwise.

You can use the Monkey Couch Guardian to guard a whole room or just your stash of snacks.

And now that you know how to use an Arduino, you can easily adapt this circuit to switch on lights or appliances in your home, yard, or workshop, by substituting the appropriate relay.

—Keith Hammond, MAKE Projects Editor

To see full build instructions, schematics, breadboard layout, and project video, visit the project page for this build: radioshackdiy.com/project-gallery/monkey-couch-guardian

TO SUBMIT YOUR OWN CREATION, EXPLORE OTHER GREAT CREATIONS AND GET THE HARD-TO-FIND PARTS YOU NEED, VISIT RADIOSHACK.COM/DIY.

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