Challenge #3: Design more complex circuits

Example 1: Make a two-way switch by changing resistance

How it works:

Fully connected circuit

• This is really TWO circuits in one. The potentiometer in the middle changes the resistance of both circuits at the same time.
• Resistance lowers (resists) the flow of electricity in a circuit. When the dial is turned all the way in one direction, the resistance in that part of the circuit is lower, causing one LED to have more current and glow more brightly while causing the other LED to have less current and dim.

You will need:

• 1 coin cell battery power tile
• 2 LED light output tiles
• 1 potentiometer input tile (or just a potentiometer, it will work fine without a cardboard tile)
• 5 alligator clip wires

Build the circuit:

1. Connect the left and right terminals of the potentiometer to the negative ends of both LED tiles.
2. Connect the MIDDLE terminal of the potentiometer to the negative end of the power tile.
   
3. Using two alligator clip wires, connect the positive end of the power tile to the positive end of both LED tiles.
4. Rotate the dial of the potentiometer to change the current between the two LEDs, as seen below:

Extend the activity:

1. Disconnect one of the LEDs. What happens to the other LED? Why?
2. Instead of a potentiometer, can you make a two-way switch tile using only binder clips?
3. Can you draw how electricity is flowing in both halves of the circuit?
4. What else could you use a potentiometer for?

Example 2: Make a circuit game to test your dexterity

How to play

• Play the game by trying to maneuver the game wand around a bent paper clip without touching it. If they touch, the motor will vibrate the game tile to let you know you lost the game!

How it works

• The two pieces of wire (the game wand and the bent paper clip) act like a switch. When they touch, they close the circuit and the game tile vibrates. The game is to keep the circuit open. What classic game works just like this?

You will need:

• 1 power tile and alligator clip wire
• 1 game tile, made with scrap cardboard, 2 binder clips, a paper clip, a small motor, and tape or glue
• 1 game wand, made with an alligator clip wire and metal ring handle from a binder clip

Build the game tile:

Game tile

1. Make an “L” shaped game tile by folding, or cutting and gluing cardboard scraps. Consider adding triangle brackets for stability (see “Side View” photo).
2. Squeeze open a binder clip and slide the motor into it, then attach to the horizontal base of the game tile. Make sure the rotor part of the motor can move freely outside the binder clip.
3. Loosely unbend the paper clip and attach to the tile’s vertical surface using a binder clip.
4. Connect one wire lead from the motor underneath each binder clip. Ensure the connections are firm. For this project, it does not matter which lead connects to which clip, although reversing the leads will change the direction that the motor spins.

Build the game wand:

Game wand

1. Detach a handle from one of the binder clips. Squeeze the sides of the handle to remove it from the clip. (You can use the rear handle from one of the clips on your game tile.)
2. Clip the handle to one end of an alligator clip wire.

Connect your tiles and play the game:

1. Connect one end of the power tile to the game wand; connect the other end of the power tile to the clip holding the motor on your game tile.

2. Play the game by trying to maneuver the loop of the game wand over the paper clip without touching. If you close the circuit, the motor will vibrate the game tile to let you know!

Next: Challenge #4