We’re celebrating the release of Chris Hackett & PopSci’s new book, The Big Book of Maker Skills. Today’s excerpt is two easy DIY sensors. – Becky Stern
Improvise a Pressure Sensor
Not to be confused with a pressure switch, which is just on or off, this analog device has a resistance that changes smoothly with the amount of pressure applied. This roll-your-own version is a classic hack from Forrest Mims. (You do know who Forrest Mims is, don’t you? If not, go find out. Right now.)
STEP 1 Snag a piece of the antistatic foam that chips (the inedible kind) are often packaged in. You can cut it to pretty much any size or shape you need.
STEP 2 Strip the ends of two wires and poke them all the way through the foam on opposite sides. Bend the protruding ends over so they don’t pull out.
STEP 3 Dip or paint the whole shebang with liquid electrical tape or PlastiDip, let it dry, and your sensor is ready to use. Connect to a microcontroller and calibrate.
Rig a Loop-Switch Booby Trap
The loop switch may be the world’s simplest sensor. It takes 15 seconds to slap one together from two pieces of insulated wire, and it’s reliably closed by pulling it taut. Use it to activate a burglar alarm to keep people out of your secret stuff, to set off a camera, or to find out who’s come a-snoopin’.
STEP 1 Strip 1 to 2 inches (2.5–5 cm) of insulation off one end of a piece of wire. Form the stripped part into a loop big enough to easily pass over another piece of the wire, and twist to secure.
STEP 2 Pass a second piece of wire through the first, strip the end again, and form another loop, this time being sure to include the first wire inside the second loop. Twist to secure, leaving plenty of room for the wires to slide back and forth.
STEP 3 Electrically connect the two wires between a power source and the load you want to activate, and mechanically between a stationary object and the door, drawer, window frame, or other movable object you want to secure. Then wait for someone to trip it!
Makers, get ready: This is your ultimate, must-have, tip-packed guide for taking your DIY projects to the next level—from basic wood- and metalworking skills to 3D printing and laser-cutting wizardry, plus the entrepreneurial and crowd-sourcing tactics needed to transform your back-of-the-envelope idea into a gleaming finished product.
In The Big Book of Maker Skills: 334 Tools and Techniques for Building Great Tech Projects, readers learn classic, tried-and-true techniques from the shop class of yore—how to use a metal lathe, or pick the perfect drill bit or saw—and get introduced to a whole new world of modern manufacturing technologies, like using CAD software, printing circuits, and more. Step-by-step illustrations, helpful diagrams, and exceptional photography make this book an easy-to-follow and easy-on-the-eyes guide to getting your project done.
Images courtesy Weldon Owen