Trying It Out

You probably have a fortune in coins just waiting to be found at the bottom of your furniture cushions, so it’s time you got this metal detector thing on the trail of all those nickels and dimes! Here’s how to make this gadget work:

1. Insert the batteries.

2. Secure the lid on the box with the screws provided and flip the on/off switch to On.

3. Holding the coil away from any metal, turn the potentiometer knob so that the LED is on, and then turn the potentiometer knob slightly in the other direction till the LED turns off.

This calibrates the IC so that it is triggered by small changes in the oscillating signal that runs through the coil.

4. Try out your detector by holding it near different items containing metal.

We were able to detect coins and keys in pants pockets as well as various types of tools and nails at a distance of about 1⁄2". You should be able to detect larger metal objects (such as a space shuttle) at a distance of about an inch.

If you don’t get the results we got, here are some options to check out:

Check that all the batteries are fresh, tightly inserted in the battery pack, and all face the right direction.

Check that no wires or components have come loose.

Compare your breadboard against the photos to make sure all the wires and components are connected correctly.

Taking It Further

Aren’t metal detectors just the most addictive thing? (Well, maybe not, but they are kind of fun to play around with.) Here are some other things you can do to have fun with detectors:

Have your detector activate a buzzer instead of an LED by simply replacing the LED in the circuit with a buzzer.

Make a more powerful detector that could find coins a few inches under the sand on the beach.

Check online for other metal detector circuits that have more oomph. www.thunting.com specializes in metal detectors you can use for hunting treasure, for example.