1+ 2+ 3 Magnetic Switches from Everyday Things _{By Cy Tymony}
Control many devices from afar with the magnetically sensitive Sneaky Switch.

You will need: Magnet, paper clip, aluminum foil, tape or foam, cardboard, wire, LED or buzzer, 3-volt watch battery or equivalent

Optional: Ring, battery-operated toy, X- 10 universal interface and appliance module

1. Make a magnetic activator. You’ll want a strong magnet to activate devices from at least an inch away. Tiny rare earth magnets can be found in most micro radio-controlled cars, and in the packaging of some hearing aid batteries. Glue a magnet to the face of a ring or a wand, or affix it to some object so that when it’s near the switch, or moved away, it will cause the desired effect.

2. Make a Sneaky Switch. In this magnetic switch, the paper clip lies across a “spring” of rolled tape, one end hovering just above the aluminum foil and the other end taped down. (A small piece of foam can also be used as the spring.) When a magnet passes over the switch, it tugs the clip to touch the foil, completing the circuit. Connect the switch to a 3V watch battery to light an LED, buzzer, or other low-current devices and toys.

Paper clip

Foil

Magnet

Ring

Rolled up tape (or foam)

LED

(or buzzer)

Watch battery

3. Connect switch to a relay.
Your magnetic switch can be attached to
a relay to control devices that need higher
current. Mount your switch and relay behind
the dashboard to secretly activate a cut-off
switch, alarm, or other car accessories. Or
hook your switch to an X- 10 controller and
universal interface module to control a variety
of appliances. Pretty sneaky!

Bonus: Detect counterfeit money. Legitimate currency has iron particles in the ink. Fold a bill so half of it stands up vertically — if the top edge moves toward your magnet, it’s the real deal. If not, phone the Secret Service!

Illustrations by Mark Frauenfelder