Lesson #1: Basic Circuits

An electrical circuit is like a NASCAR raceway.  The electrons (racecars) zip around the race loop (wire circuit) superfast to make stuff happen.

Although you can’t see the electrons zipping around the circuit, you can see the effects: lighting up LEDs, sounding buzzers, clicking relays, etc.

There are many different electrical components that make the electrons react in different ways, such as resistors (limit current), capacitors (collect a charge), transistors (gate for electrons), relays (electricity itself activates a switch), diodes (one-way street for electrons), solenoids (electrical magnet), switches (stoplight for electrons), and more.

We’re going to use a combination diode-light-bulb (LED), buzzers, and motors in our circuits right now. A CIRCUIT looks like a CIRCLE.  When you connect the batteries to the LED with wire and make a circle, the LED lights up.  If you break open the circle, electricity (current) doesn’t flow and the LED turns dark. LED stands for “Light Emitting Diode”.  Diodes are one-way streets for electricity – they allow electrons to flow one way but not the other.

When electric current passes through a material, it does it by electrical conduction. There are different kinds of conduction, such as metallic conduction, where electrons flow through a conductor (like metal) and electrolysis, where charged atoms (called ions) flow through liquids.

Here's what you need:

• 2 AA batteries
• AA battery case
• 2 alligator wires
• LEDs (any you choose is fine)

Download Student Worksheet & Exercises

Be alert for:

•  Batteries inserted into the case the wrong way!
•  LED in the wrong way (LEDs are picky about plus and minus - they are POLARIZED)
•  Is there a metal-to-metal connection?  (You're not grabbing ahold of the plastic insulation, are you?)
• Bad wires can cause headaches - if all else fails, then swap out your alligator clip lead wires for new ones.

Exercises

1. What does LED stand for?
2. Does it matter which way you wire an LED in a circuit?
3. Does the longer wire on the LED connect to plus (red) or minus (black)?
4. Do you need to hook up batteries to make a neon bulb light up?  Why or why not?
5. What's the difference between a light bulb and your LED?
6. What is the difference between a bolt of lightning and the electricity in your circuit?
7. What is the charge of an electron?

Lesson #2: Simple Switches

When you turn on a switch, it’s difficult to really see what’s going on… which is why we make our own from paperclips, brass fasteners, and index cards.

Kids can see the circuit on both sides of the card, so it makes sense why it works (especially after doing ‘Conductivity Testers’).

SPST stands for Single Pole, Single Throw, which means that the switch turns on only one circuit at a time. This is a great switch for one of the robots we’ll be making soon, as it only needs one motor to turn on and off.

Think of this switch like a train track. When you throw the switches one way, the train (electrons) can race around the track at top speed. When you turn the switch to the OFF position, it’s like a bridge collapse for the train – there’s no way for the electrons to jump across from the brass fastener to the paper clip. When you switch it to the ON position (both sides), you’ve rebuilt the bridges for the train (electrons).

Troubleshooting:

The two tabs on the back of the motor are the places to clip in the power from the battery pack. Since these motors spin quickly and the shaft is tiny, add a piece of tape to the shaft to see the spinning action more clearly.

Kids can make their own switches so they can trace the path the electricity takes with a finger. See what you think about this SPST:

Here's what you need:

• 2 AA batteries
• AA battery case
• 3 alligator wires
• index card
• 2 brass fasteners
• paper clips
• buzzer, motor, or LED

Download Student Worksheet & Exercises

Exercises

1.  If you want to reverse the spin direction of a motor without using a switch, what can you do?
2.  A simple switch can be made out of what kinds of materials?
3.  How would you make your SPST switch an NC (normally closed) switch?
4.  How did you have to connect your circuit in order for both the LED and motor to work at the  same time? Draw it here:
5.  Draw a picture of your experiment that explains how the SPST switch works, and show how electricity flows through your circuit.

Extra credits(for students who have completed Part 3):

6. Draw a picture of your experiment that explains how the DPDT switch works in your circuit and show how to wire up the circuit.

Lesson #3: Wiring Up Motors

Imagine you have two magnets. Glue one magnet on an imaginary record player (or a ‘lazy susan’ turntable) and hold the other magnet in your hand. What happens when you bring your hand close to the turntable magnet and bring the north sides together?

The magnet should repel and move, and since it’s on a turntable, it will circle out of the way. Now flip your hand over so you have the south facing the turntable. Notice how the turntable magnet is attracted to yours and rotates toward your hand. Just as it reaches your hand, flip it again to reveal the north side. Now the glued turntable magnet pushes away into another circle as you flip your magnet over again to attract it back to you. Imagine if you could time this well enough to get the turntable magnet to make a complete circle over and over again… that’s how a motor works!

After you get the buzzer and the light or LED to work, try spinning a DC motor:

Here's what you need:

• 2 AA batteries
• AA battery case
• 2 alligator wires
• 1.5-3V DC motor
• optional: propeller

Lesson #4: Dimmers and Motor Speed Controllers

So now you know how to hook up a motor, and even wire it up to a switch so that it goes in forward and reverse. But what if you want to change speeds? This nifty electrical component will help you do just that.

Once you understand how to use this potentiometer in a circuit, you'll be able to control the speed of your laser light show motors as well as the motors and lights on your robots. Ready?

Here's what you need:

• 2 AA batteries
• AA battery case
• 3 alligator wires
• potentiometer
• 1.5-3V DC motor
• LED (any you choose)

Download Student Worksheet & Exercises

Exercises

1. How does a potentiometer work?
2. Does the potentiometer work differently on the LED and the motor?
3. Name three places you’ve used potentiometers in everyday life.
4. How do you think you might wire up an LED, switch, and potentiometer?

Lesson #5: Forward and Reverse Motor Control

Once you've made a a simple switch, you're ready to use more advanced electrical components, such as the DPDT switch you picked up from an electronics store (refer to shopping list for this section). When you wire up this nifty device, you'll be able to get your motors to go forward, reverse, and stop... all with the flip of a switch.

You can use this component along with a potentiometer so you can not only control the direction but also the speed of a motor, like in a robot or laser light show. And don't feel limited on using this switch just with motors - it works with bi-polar LEDs and other things as well.  For example, you can hook this up so that when it's in the UP position, the buzzer sounds, and the DOWN position makes the headlights go on. Are you ready to learn how to wire this one up?

Lesson #6: Electric Eye

This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.

A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it "sees".

Photoresistors are very inexpensive light detectors, and you'll find them in cameras, street lights, clock radios, robotics, and more. We're going to play with one and find out how to detect light using a simple series circuit.

Materials:

• AA battery case with batteries
• one CdS cell
• three alligator wires
• LED (any color and type)

Download Student Worksheet & Exercises

Turn this into a super-cool burglar alarm!

Exercises

1. How is a CdS cell like a switch? How is it not like a switch?
2. When is the LED the brightest?
3. How could you use this as a burglar alarm?

Lesson #7: Waterbots

Of the robots we’re going to build, waterbots have the highest instant-success rate. You basically attach a motor to a piece of foam, stick it in the water, and it either floats and zips around, or capsizes and acts like an odd submarine.

Either way, kids shriek with delight that their creation actually moves. We're going to use foam to create a waterbot, which will be powered by a simple electrical circuit.

The hardest part of this activity will actually be building it stable enough so it doesn't capsize. Boats are always built in a way so they don't get pushed or flipped over easily by carrying a ballast, or extra weight, at the lowest part of the boat. You'll need to figure out where to out your motor and batteries (which weigh a lot compared to a foam block) in order to balance your boat.

One of the biggest hurdles to overcome when building junkyard robots is friction. Since the motors have high speed and low torque, they can be difficult to use without a gearbox (which is both hard to find and out of the scope of this class). Since water has little friction, the robot will move about quite easily in the wet environment.

We offer kids waterproof materials to build their robots with so that in the event their invention has trouble moving, we usually toss it in the pool to see if it can swim… which sparks another avenue of creativity and another round of improvements. Just be sure to keep the batteries out of the water. Are you ready?

Materials:

• 1 propeller (read comments for ideas on where to find one)
• foam block (this can be a scrap piece from packing material)
• 3VDC motor
• AA battery case with AA batteries
• 2 alligator clip lead wires
• hot glue gun with glue sticks

When you stick a block of wood in the water, it floats. If you make a small bowl out of tinfoil and place it in the water, it will also float. But if you crumple up the foil into a ball, it sinks. Certain materials like ice, wood, and foam blocks float no matter what shape they are.

Some materials use their shape to decide whether they sink or float. A block of steel will usually sink unless you shape it into a boat (think about gigantic oceanliners!) Clay works the same way, as do many materials. So why is that?

Let's take a look at our steel example. Steel is more dense than water. One pound of water takes up more space than one pound of steel, so it sinks when you place it in water. When you shape the steel into a boat, the steel fills with air. Steel and air together are less dense than water, so your oceanliner floats.

Hot tips for wet robots: You won’t get shocked by placing the batteries in the water – the amperage is too low. The motors are completely safe to submerge in the water, but they won’t last more than a few weeks from this treatment so stock up on a few extra.

You can waterproof the motors (seal holes on motor with electrical tape, insert into a tight-fitting canister with a snap-on lid, seal with silicone, punch hole in lid, solder wires to terminals, let dry, snap on lid), but it’s often more trouble than it’s worth.

Lesson #8: Jigglebots

Ever wonder how a cell phone vibrates? What mechanism could be in such a tiny space to make the entire phone jiggle around? Well, there’s a tiny motor inside with an off-center weight on the shaft, called an eccentric drive. You can still see eccentric drive mechanisms in older steam engines where the rotational motion is converted to liner? movement. Eccentrics are also found on tandem bicycles with timing chains. Kids can make this robot in less than five minutes, but it will take hours to get all their modifications and adjustments just right. This robot works by wobbling, and the sloppier the kids are in their construction, the better the robot dances around. Play with the placement of the weight (battery pack) and the legs. Add more skewers, adjust their position and angle until you get it dancing without toppling over.

Materials:

• 10 (or more) skewers
• foam block
• 3VDC motor
• wooden clothespin
• AA battery case with AA batteries
• 2 alligator clip lead wires
• hot glue gun with glue sticks
• Optional: gear that fits onto the motor (you can alternately drill a hole in the clothespin as shown in the video)

Start building your dancing jigglebot by watching this video:

Most kids will make the legs parallel to the vertical, but quickly find that having the skewers flared out makes for a more stable design. Some jigglebots will spin in circles, others just stand and shake, and still others will zip off at a good pace in a straight line. We use a clothespin so you can add more weight (clip something inside the clothespin) if you need to. Tip: The 'sloppier' kids build this robot, the better it moves. Enjoy!

Lesson #9: Artbot

This is a fun variation of the Jigglebot that uses markers for legs so it can scrawl you out a masterpiece as it entertains you with its curious dance.

Materials:

• foam block
• 5-8 markers
• AA battery case with AA batteries
• alligator clips
• 3V DC motor
• wood clothespin
• hot glue gun
• scissors or razor

Lesson #10: Amphibious Robot

Amphibious vehicles is a craft which travels on both land and water. And it doesn't need to be limited to just cars. There are amphibious bicycles, buses, and RVs. Hovercraft are amphibious, too!

Amphibious crafts started back in the 1800s as steam-powered barges. In the 1950s, the German Schimmwagen was a small jeep that could travel in water as well as on land. The most popular amphibious vehicle on the market is the 1960 Amphibicar (photo shown left) and later the Gibbs Aquada.

The secret to making an amphibious vehicle is this: it must be designed so it floats in water (it must be watertight and buoyant) and robust enough to travel on land. Many amphibious creations either leaked, sank, or never made it off the drawing board. But that's what being a scientist is all about: coming up with an overall goal and figuring out a way to overcome the problems faced along the way.

We're going to build our own version using items like water bottles and hobby motors. Are you ready?

Materials:

• foam block (at least 2" x 6")
• propeller
• straw
• two wood skewers
• four wheels (tops from milk jugs, yogurt containers, etc)
• 3V DC motor
• propeller
• 2 alligator clip leads
• AA battery case with 2 AA batteries
• hot glue gun
• scissors

Lesson #11: Propeller Car

The great news is that many of the problematic airplane troubles were figured out a long time ago by two amazing people: the Wright brothers.

The Wright brothers also took an airfoil (a fancy word for “airplane wing”), turned it sideways, and rotated it around quickly to produce the first real propeller that could generate an efficient amount of thrust to fly an aircraft.

Before the Wright brothers perfected the airfoil, people had been using the same “screw” design created by Archimedes in 250 BC. This twist in the propeller was such a superior design that modern propellers are only 5% more efficient than those created a hundred years ago by the two brilliant Wright brothers.

We're going to use a propeller on our basic race car chassis (frame) to see how much thrust we'd need to make it move. If you don't want to make the fancy triangle-shaped body frame, you can substitute a foam block or two (which will make your car able to go in water, too!)

Are you ready?

Materials:

• 4 popsicle sticks
• 2 straws
• 4 wheels or lids from film canisters, or milk jug lids (anything plastic, round, and about the size of a quarter)
• 1 propeller
• 2 skewers
• 1 film can or foam block
• 3VDC motor
• AA battery case with AA batteries
• 2 alligator clip lead wires
• hot glue gun with glue sticks

Need help finding propellers? Rip one off an old fan or toy airplane, such as a balsa flyer.

Lesson #12: Bristle Brush Bot

This is the simplest robot you can make... out of old parts from around the house. While this little robot doesn't use energy from the sun or wind, we've placed it here with other alternative energy projects because the parts come from the trash bin. This project is an extension of the Jigglebot robot from Unit 10.

You'll need to find:

• Old toothbrush you can destroy
• Tiny vibrator motor (you can rip one out of an old cell phone) - just make sure it's got a weight attached to the motor shaft.
• Small watch battery (make sure it's around 3V to match the motor)
• Scissors and/or razor
• Tape and a hot glue gun
• Optional: Paper clips for claws and feet

Here's what you do:

What’s going on? Your BristleBot uses the toothbrush bristles as legs and an eccentric motor to shake and wobble it by tiny amounts to look like a smooth motion. The larger the weight, the more you’ll see the wobbling action. Try making one out of the head of a scrub brush or small broom!

Lesson #13: Robot Cable Car

A cable car transports people or things in a vehicle that uses a strong cable to pull at a steady speed. Also called aerial lift, aerial tramway, or gondola, these are different from the cable cars associated with San Francisco, which use buried cables to move the car up steep streets. The world's longest working cable car is in Sweden and covers 26 miles. Sweden used to operate a 60-mile cable car, but only a 8.2 miles (13.2 km) of it still works today, however this section is the longest passenger cable car in operation currently. We're going to make a durable cable car that can travel as long as you have string for it to move along! It's really a cool and simple project, and you can add cups or berry baskets below to transport cargo. Here's what you need to do:

Materials:

• 6 popsicle sticks
• AA battery case with 2 batteries
• two 3VDC motors
• tack
• scissors
• string
• hot glue gun
• glue stick for glue gun and also another one for use in the project itself (watch the video)
• two alligator clip wires (four if your motor does not have wires comes out the end but tabs instead)

Lesson #14: Fast Ferry

The ferryboat was one of the ways folks got from island to island. Usually ferries make quick, short trips from one spot to another, picking up cars, people, or packages and transporting them across the water. In Venice, you'll hear the ferry also referred to as the "water bus" or "water taxi".

Ferries that travel longer distances usually transport cars and trucks. If you live in a waterside city or group of small islands, then the ferry is probably in your daily routine, because they are much cheaper than building complicated bridges or underwater tunnels.

Some ferries don't have a "front" and "back", but are double-ended and completely reversible, which allows them to shuttle back and forth across short distances without turning around. You'll find these ferries in Australia, British Colombia, and Washington state.

There are many different types of ferries, including hovercraft, hydrofoils, and catamaran. Hydrofoils (shown in the image above) have special "wings" attached to the bottom of the boat that actually lift the boat out of the water when the speed increases. The special wing is designed to work in water and generate enough lift to move the massive boat out of the water so only a small part of the wing remains in the water to minimize friction (drag) force on the boat. With less friction, the boat can go even faster!

We're going to make a simple ferry that works in the pool or bathtub. Don't forget to add a remote control with extra-long wires!

Materials:

• 2 water bottles
• 2 alligator clip leads
• 3V DC motor
• propeller
• AA battery case with AA batteries
• popsicle sticks

Lesson #15: Catamaran

Catamarans are boats with two or more hulls that are strapped together and move by either wind power (using sails) or engine power. They are one of the first boats humans ever floated in. Catamarans are used when speed and large payloads are needed: their interesting geometric design (their balance is based on geometry, not weight) allows them to glide through the water with lower friction and carry more than single-hulled boats. We're going to create two different versions of the catamaran, mainly depending on how many water bottles you have available. Put these in a swimming pool and watch them zoom!

Materials:

• 2-4 water bottles
• 3V DC motor with propeller
• AA battery case with AA Batteries
• hot glue gun
• alligator clips
• popsicle sticks

Lesson #16: Race Cars

Racerbots can steer, unlike the Jigglebot. If you have more than one motor on your robot frame, you can turn either left, right, or spin on command. Wired remote control instructions follow this project.

The wheels need to be squarely set on their shafts, all wheels need to be parallel, long wires out of the way, the motors spinning in the right direction, the battery pack in the right position... does this sound like a headache yet? Pay attention to construction details in the video and you’ll have less to fix later on.

Construction Tip: Cut the dowels in half to use for the axles and use the milk jug lids or film canister tops for wheels (you can also rip small, lightweight wheels off an old toy if they are about the size of a quarter). You may need to sand the dowels slightly if they are hard to fit into the wheels.

Materials:

• 4 popsicle sticks
• 1 straw
• 4 wheels or lids from film canisters, or milk jug lids (anything plastic, round, and about the size of a quarter)
• 1 skewer
• Two 3VDC motors
• AA battery case with AA batteries
• 2 alligator clip lead wires
• hot glue gun with glue sticks

Troubleshooting: To increase your motor speed, you’ll need to add a second battery pack. If you find the back wheels are slipping, run a bead of hot glue around the circumference of each wheel and carefully lay the flat side of a cut rubber band around the wheel (trim excess).

If the wheels spin in the opposite direction, your car will spin donuts (which could be fun!). If the car doesn’t move at all, use the basic circuit troubleshooting tips covered in previous experiments. (Are the batteries in the right way? Metal-to-metal connection? Fresh batteries? New wires?)

Check to see if all four wheels spin freely without power. Roll the car down a ramp – does it travel relatively straight? If your robot keeps tripping over its wires, wrap the long lengths around the popsicle sticks or use shorter wires (cut in half, strip the insulation off, twist the exposed metal end on your electrical connections, and secure with tape).

What’s the next step? The instructions here are just for the chassis and propulsion systems of your robots. We’ll help you with the body framework and getting the robot to move. It’s up to you to add eyeballs, tentacles, claws, or whatever else you want to this framework.

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