## Introduction: Switches in Series

Making circuits with copper tape can be as illuminating as it is easy. Using a power source, switches, and a light, you can get the feel for a basic circuit.

## Step 1: Tools and Materials

• Copper tape -- available as slug and snail tape at home supplies stores
• Coin cell battery -- CR 1220 with PCB terminal pins, they cost about one or two dollars at DigiKey or 50 for £30 at Bare Conductive.
• LED
• Switches -- Check out https://www.instructables.com/id/Knob-Switch/
• Pencil
• Scissors or Craft Knife
• Paper clip for poking holes
• Index card
• x2 3/8" fasteners

## Step 2: Sketch Your Circuit

Draw a circuit diagram. The diagram will have a one-to-one relationship with the actual circuit — a big benefit of working with copper tape.

## Step 3: Make the Traces

Cut tape strips to 1/4". Cover your traces to make a loop where electricity flows. Cut out 3/8" (10mm) spaces with your scissors or craft knife for the components: battery, LED, and two switches.

## Step 4: Make the Knob Switches

Fold a 3/8" x 3" strip of card stock into quarters. Make a triangle shape by layering two of the folds at the bottom and adding a strip of copper tape. Use the paper clip make a small hole in the center. For more detailed instructions, check out https://www.instructables.com/id/Knob-Switch/.

In the middle of the switches gaps, punch holes with the paperclip, and add your knob switches. Peel a few more strips to connect the pins of the battery and the leads of the LED to the base layer of copper tape.

Make sure the polarity of the battery and LED matches. That is, the positive end of the battery should connect to the positive end of the LED. The top pin of the battery is marked with the "+"/positive sign. The positive lead of the LED is the longer side.

## Step 6: Check It Out

When the switches both have solid contacts with the copper tape to the battery and LED, the circuit will be complete and the LED will shine.

## Step 7: Meditations and Variations

Switches in series are essentially an AND gate. You can use them to construct truth tables and do all sorts of things like figure out if Dave has brown eyes what kind of cigarette he smokes. For complex problems you'll need different logic gates, like an OR gate, which will be my next circuit, "Parallel Switches."

You can also add more LEDs to the circuit, or perhaps run a small motor. See what type of materials will carry current across a small gap.