TinkerCAD Circuits I was providing support at a school campus when I was asked by a teacher to help with an interactive display board. I noticed she was teaching a lesson on basic circuits using a light bulb, switch, and battery. The lesson was going well but some light bulbs didnâ&#x20AC;&#x2122;t work and some batteries were drained. The kit was obviously old and needed updating. I pulled the teacher aside and demonstrated Tinkercad Circuit simulator. I demonstrated how to build the same circuit in a few minutes and how to test the circuit. She was immediately sold on the simulator. We took the students to the site, they logged in with their Google account and started assembling their circuit. It was at this time that I realized I needed to revisit Tinkercad. I wrote an issue on Tinkercad for electronics back in April of 2018. The issue covered the basic blinking LED and Arduino integration. I felt there was a need to develop another issue which covered some of the basics in a little more detail.

Alex Reyes

Cover Image Attribution Background photo created by asierrelampagoestudio - www.freepik.com

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Digital Maestro Magazine - Alex Reyes

Basic LED Circuit.................................. 11 Using A Switch....................................... 17 Color Coding......................................... 18 Title Your Project................................... 19 Extending the Activity...........................20

Capacitors............................................ 21 Capacitor Circuit.................................... 22 Extend the activity................................. 26

Transistors............................................ 27 Switches................................................. 28 Amplification.........................................30 Extending the Activity........................... 33

Digital Maestro Magazine - Alex Reyes

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Introduction This issue reviews the assembly of a basic circuit with an LED and push button. We compare the use of a push button and a switch in the same circuit. The lesson emphasizes how closed circuits work and the flow of current through a circuit. The circuit uses a resistor to limit the amount of current flowing through the LED. The resistor demonstrates how we limit the flow of current through a circuit. Students understand that current is something that flows through a circuit event if we canâ&#x20AC;&#x2122;t see it flowing. There is an animation below that shows how current flows through our basic LED circuit. I used an app to create the circuit simulator. In the next lesson, we assemble a circuit with a capacitor. A capacitor stores energy much like a battery. This energy is the potential energy that is released as current and kinetic energy. The purpose of the lesson is to demonstrate how energy is stored and released. The third lesson focuses on the transistor as a switch. Transistors are commonly used in computers. This lesson uses a common transistor to light an LED. The lesson is divided into two parts. The first part uses one power source to trigger the transistor and light the LED. The second part uses two power sources. A low power source of 1.5 volts is used to trigger the transistor. A second power source of 6-volts is used to light the LED. The LED in the second part is much brighter because of the second power source. Students understand that closed circuits are formed with closed loops using physical and electronic switches.

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Digital Maestro Magazine - Alex Reyes

Tinkercad Tinkercad is an online development tool for 3D models. It is also a development tool for circuits. The development environment is easier to use than similar tools used by professionals. It’s intuitive for students to use. The lessons in this issue will focus on the electronic circuit development environment. This environment has components to construct a variety of electronic circuits. We can assemble and test these circuits inside the development environment. There are many benefits to using an online development and simulation environment. The service is available online so there is nothing to install. The computer should have the latest browser installed. There is no specific browser requirement. The service is free. The components don’t break. We are free to make mistakes. The environment is safe. We don’t have to worry about students sticking themselves with the points of LEDs or transistors. No electronic shock from the battery current.

Digital Maestro Magazine - Alex Reyes

A drawback is that the development and testing environment is digital. Studies show time and again the importance of kinesthetics. Kinesthetic learning is where students interact with learning by touching and interacting with objects. Students are engaged in active learning. In my experience, students learn better when they interact with the content. Using an online simulation is not enough. The online skills don’t always transfer from the simulated world to the real world. There are lots of reasons for this and one reason is the lack of context. Learning skills must be applied to real-world situations. There needs to be a connection to real-world situations and problems. I recommend combining the online development of circuits with actual hands-on using real components and circuits. Electronic circuits are relatively inexpensive. A box of 300 LEDs on Amazon costs as little as \$9 US dollars. A box of over 500 resistors costs about the same. An assortment of

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TinkerCAD Circuits capacitors costs about \$13 dollars. A pack of six mini breadboards runs about \$5. Find an old radio in a second-hand store and open the back. Expose the electric components. Donâ&#x20AC;&#x2122;t plug the radio to a power source when doing this. Remove any batteries too. Identify the components and discuss their purpose.

Studying the components in a circuit ties in very nicely when discussing systems. How do the components contribute to the functioning of the radio? How would the removal of one component affection the functions of the radio? How is this similar to other systems?

Select the option to sign in with a social media provider account.

Sign in with your email account credentials. If you are using a Google account and are using the Chrome browser then you will be presented with your account information. Click the account you want to use. Most people have one account. You

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Digital Maestro Magazine - Alex Reyes

The Circuits portal has a nice big green button. Click this button to create a new circuit.

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Circuit Simulator The circuit simulator is simple. The main area has a development canvas. All the available components are found in a panel on the right side. There is an extensive list of components. The basic components are displayed for us to begin basic projects. Some of these components include LEDs, switches, resistors, and batteries. There is a search box above the component list. The search box is useful when we need to find a specific component in the much larger list of components. There are four buttons above the list of components. One of the buttons is used to start the simulation after we construct a circuit. When everything is ready we press the Start Simulator button. This activates the simulated battery current and the effects that result from the flow of current. We need to press this button to begin the simulation every time. We need to stop the simulation when we want to make any changes to the circuit. Like in real life, we should not work on a circuit when current is flowing through it.

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The Breadboard A breadboard is used to develop circuit prototypes. It provides a place for us to connect components and hold them in place. No soldering is required. Without a breadboard, we would have to connect components with clips or bare wire. These are not ideal ways to connect components. The breadboard makes the job of creating circuits much easier. The term breadboard comes from the early days of electronics and prototype development. Hobbyists would use screws and nails on old breadboards to hold components and wires in place. Breadboards were made of wood. The breadboards used for electronic prototyping today are made of a plastic case. Inside the case, we have metal clips that hold components and wires. For those of you that don’t know. A breadboard was at one time used to slice bread. This is when you made your own bread or purchased bread at a bakery. Before building projects on a breadboard we should find it in the components panel and place it on the work area. Scroll down the list of components and find the small breadboard. Click and drag the board onto the work area. We can also click the board once and it will attach itself to our mouse pointer. Place the board near the center of the work area.

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Let’s take a closer look at the board. It is important that we understand how the board works. The board is a plastic rectangular box. The box has holes placed in patterns.

There is a series of holes between red and black lines. These holes between lines are on opposite ends of the breadboard. The end of each line has a Plus or Minus symbol. The plus is red and the minus is black. These colors are important. They are a standard used by most circuit designers. The holes along the red line carry current from the positive side of a battery terminal. The holes along the black line carry current along the negative side of the battery terminal.

Let’s take a look at what is going on inside a breadboard. Under each of the holes is a metal clamp. This clamp holds the wires we insert into the holes. The clamps are all connected together. We can use any hole to pass current to any of the components. In the diagram, I am showing that voltage is flowing in from the positive terminal. The current can flow in from any of the holes on the board. The current is distributed to all the other clamps. Once we connect a component, the current flows up the clamp and into that component.

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TinkerCAD Circuits We are accustomed to thinking that electric current flows from the positive terminal of a battery to the negative terminal. Electric current does flow from the positive terminal to the negative but the concept is backward. Electrons flow through circuits. Electrons have a negative charge. They flow toward the positive end of the battery. When electricity was first discovered it was thought that electric current had a positive charge. We later found that the electric current has a negative charge. By that time it was too late and the symbols for current flow have remained the same for most people. The positive battery terminal is filled will electrons flowing out and going to the negative end of the battery which is filled with protons. Protons have a positive charge.

Here is another sliced look at the breadboard. This view shows the positive and negative buses on both sides. A bus in electronics terms is a metal conductor that transfers electric current to components.

Each positive and negative connector is a bus that transfers current to each component that touches any point on the bus. Our components are assembled into circuits using connectors in-between.

The holes and clips between these two rails work much the same way. The difference is that the clips connect horizontally. The holes in the center are organized in a grid. The columns are labeled from A to J. The rows are numbered from 1 to 30 on this board. The board is split in two. There is a divider running down the middle. This divider is there so we can assemble multiple projects on one board. We can assemble a project using columns A through E and others using columns F through J. We can bridge this gap using a jumper wire. We will talk about jumper wires once we begin working on the first project.

The best way to learn how a breadboard works is by using it to develop projects.

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Basic LED Circuit The basic LED circuit is my favorite when introducing any project to teachers and students. It provides a good introduction to the basic layout and components in Tinkercad. The circuit is simple and familiar to most people. Basic and advanced components are located in the right panel. Some of the basic components include LEDs, switches, batteries, and resistors. They form the basis of a simple LED light switch. LED stands for Light Emitting Diode. A diode is a component that permits current to flow in only one direction. Current flowing through an LED emits light.

Digital Maestro Magazine - Alex Reyes

This LED light switch will be our first project. The LED is one of the first components in the list. Click the LED component once. It will attach itself to the mouse pointer.

Move the mouse pointer and LED over the breadboard. The Leads on the LED will want to attach themselves to the holes in the breadboard. Place the LED near the center divider. Donâ&#x20AC;&#x2122;t worry about placing the LED in the same location as the one shown in my image. There isnâ&#x20AC;&#x2122;t anything magical about the location where

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TinkerCAD Circuits I placed the LED. Leads on a component are the wires used to connect to other components. Leads in our components will attach to the breadboard rails to form circuits. The difference between an LED and a light bulb is important. The differences provide a good opportunity to teach a few concepts. A light bulb uses a filament to generate light. Light is emitted when the filament heats up. It heats up because of the current going through the filament. The filament is made of an impure metal. This impurity facilitates the flow of electrons and the resistance of electrons at the same time. There is enough resistance to cause heat and light but not so much as to prevent current from flowing through the bulb. It is the resistance that causes the filament to heat up. The heat generated causes the filament to glow. The glow is what provides the visible light we see. An LED is different from a light bulb because it does not use a filament. It does not rely on resistance to generate light. It uses a semiconductor to facilitate the flow of current. The semiconductor consists of two materials. One is called a P-type semiconductor and the other is an N-type semiconductor. They are joined together inside the plastic container. Electrons flow through the negative side of the LED and excite the electrons on the N-type conductor. They are forces across to the other side with the P-type conductor. There are holes on the P-type connector where the electrons are forced to flow. The holes are smaller than the electrons. In order to go through these holes, the electrons must lose energy. This energy is given off in the form of photons. Light is composed of photons. The amount of energy released determines the color emitted by the photons.

The colors in the spectrum of light are represented by different energy levels. Lower energy emits red colors. Higher energy emits blue colors. The light waves in the red spectrum have lower wavelengths.

LEDs don’t use lots of energy. They also don’t have much resistance. A lightbulb uses resistance to generate heat and an LED does not. The typical LED we use in a project like this one are sensitive to too much current flowing through them. We need to control the amount of current flowing through an LED. To control the flow of current we need to use a resistor. Select the resistor component and move it onto the breadboard. At this point in the lesson, we have a discussion about the resistor we need to include in the circuit. What is the purpose of the resistor in the circuit as it relates to the LED? Why didn’t we need one when using a light bulb? Is heat generated in the resistor as current flows through? If heat is generated in the resistor they why doesn’t it glow like a light bulb? The placement of the resistor is important. The LED has two Leads. One of the Leads is bent. This lead is called the Anode. The other Lead is called the cathode. We send current through the LED into the Anode. This is where we connect the positive battery terminal. This follows the flow of electrons from the battery.

Light bulbs use resistance to generate heat and light. LEDs don’t use resistance. This is why they are cooler than light bulbs and use less energy.

An LED is a diode and diodes allow the flow of current in only one direction. This direction is from the Anode to the Cathode. The

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TinkerCAD Circuits Anode Lead on an actual LED is longer than the Cathode. The Anode lead is not bent. The Anode in the simulator is bent so we can more easily identify it when assembling our circuit. Place the resistor so it lines up with the row that has the Anode on the LED. The other end of the resistor will connect to the positive connector. Current will flow from the positive clips into the resistor. The flow of current is reduced in the resistor and the reduced current flows out the other end. It goes into the clip in the row and into the Anode end of the LED. The current will flow through the LED and exit the LED through the Cathode.

demonstrates that all the holes in that row are connected inside the breadboard.

Click once on the hole in the row with the Cathode and drag the mouse pointer toward the negative terminal rail. A green line follows our mouse pointer. Click once on the negative rail to anchor the other end of the lead wire. Donâ&#x20AC;&#x2122;t click again anywhere because this will cause another lead wire to be created. Press the ESC key on our keyboard to cancel if this happens.

The image below uses arrows to demonstrate the flow of current.

We have all the elements in place for our basic LED circuit. It doesnâ&#x20AC;&#x2122;t have a switch yet. I will save that for later. We need a battery to supply the current.

To complete the circuit we need to connect the Cathode end of the resistor to the negative side of our breadboard. To do that we need a jumper wire. A jumper wire is used to bridge connections and gaps in our project. Move your mouse pointer over the row where the Cathode of the LED rests. The hole where our pointer is resting is highlighted with a red square. The other holes are highlighted with green circles. This

Digital Maestro Magazine - Alex Reyes

Go to the components panel, find a battery and place it next to the breadboard. There are three battery options available. Most students chose

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TinkerCAD Circuits either the 9-volt battery or the Double-A battery. One of these will work fine. I recommend using the 9-volt battery because the connections make work best for the next step. Our LED will also shine a little brighter. Students always like that part. The third battery option is a coin-sized battery.

Repeat the process with the positive end of the battery terminal.

The circuit is complete. To light the LED we need to start the simulation. The simulation is like an ON switch. Click the Start Simulation button.

Itâ&#x20AC;&#x2122;s easy to remove components from the work area. Click once on the component and press the delete key on your keyboard. You can also click the trash can icon in the button bar.

The LED will glow in our simulated circuit. Stop the simulation by clicking the Start Simulation button again.

Attach a jumper wire from the negative rail on the breadboard to the negative end of the battery terminal.

One of the benefits of working with simulations is that we can make mistakes. Mistakes provide learning opportunities with no expense. We used a resistor to limit the flow of current into the LED.

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TinkerCAD Circuits Without a resistor in place, the LED would burn out and possibly blow. I have seen actual LEDs give off smoke from all the heat. Click and drag the resistor to the right. Place it a few rows down.

Add a jumper wire from the row with the Anode to the positive rail.

Start the simulation and observe what happens to the LED. The explosion symbol over the LED means that we sent too much current to the LED. A real LED will not work anymore if this happens. Stop the simulation. Weâ&#x20AC;&#x2122;ll add a button so we can use it to turn the LED ON or OFF.

button. It has a circle in the center of a square. Place the push button to the right of the LED. We will use the button to bridge the center division of the breadboard. Half of the button should be on one side and the other half on the other side.

We need to move our components around the board to complete the circuit. Move the LED so the Anode lead is on the same row as the lead for the left side of the switch.

Move the resistor to the other side of the board. Align the resistor to the right lead of the push button. One end of the resistor needs to connect to the positive rail on the board.

Weâ&#x20AC;&#x2122;re going to build on the same circuit to learn how to attach a button. This button will close and open the circuit. The button used in the simulator is a little different from traditional buttons. Go to the components panel and look for the push

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TinkerCAD Circuits We need to reposition the two jumper wires. The jumper wire that connects to the LED Cathode lead needs to connect to the negative rail.

Click once on the jumper wire. Circle handles appear at each end of the wire. Use the handle on the positive rail to move the end of the wire to the negative rail.

Click once on the jumper wire to the left of the one we positioned. Click and drag the top of the wire to the right.

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Place the wire near the jumper wires for the battery. Connect it to the positive side of the rail.

Move the other end of the wire to the other side of the board and connect it to the positive rail too. This is how we distribute current to both sides of the board when using one battery.

Letâ&#x20AC;&#x2122;s take a closer look at the push button connection. Think of the button like a road with two lanes. Current flowing in each lane will flow uninterrupted. The current flowing through the right lead is not prevented from flowing through the button. The current cannot go to the other lead, the one on the left, unless the button is pressed. Pushing the button closes the circuit and current flows from the right lead to the left lead. Like a car changing lanes.

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TinkerCAD Circuits Press the Start Simulation button. Press the push button with your mouse to light the LED. Keep the button pressed on your mouse to keep the LED light. Release the button to turn OFF the LED.

Using A Switch

The center lead on the switch is called the Common. This is where the current flows into the switch.

The leads on either side of the switch are called terminals. The lead on the left is called Terminal 1. The one on the right is called Terminal 2.

The LED remains light as long as we keep pressing the button. A switch is another way to light the LED without keeping our finger or the arrow on the push button. Weâ&#x20AC;&#x2122;ll replace the push button with a switch. Click once on the push button and press the delete key on your keyboard. Go to the components panel and find the switch. Connect a jumper cable from Terminal 1 to the Anode on the LED.

Place the switch on the board. Place the center lead on the switch in the same row as the resistor. Place it in the column above the resistor.

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TinkerCAD Circuits There is a slider on the switch. The slider is currently connecting the Main to Terminal 1. This is creating a closed circuit. Click the Start Simulation button. The circuit is closed and the LED will light.

Color Coding This project used a handful of jumper wires. It is easy to track where the wires connect. Complex prototypes might have a dozen jumper wires. We are going to color code our wires to make it easier to distinguish the wires later. Color coding wires will be important in the next two projects. Click once on the jumper wire connected to the positive battery terminal to the breadboard.

Slide the switch to the right to turn OFF the LED. Click once on the slider.

At this point, we have a discussion about the different ways to close a circuit. The options include connecting directly to a power source, using a push button, and using a switch.

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There is a color selector that appears after we select a jumper wire. Click the color selector and choose red. The terminal on the battery is red. Red is usually used to denote a positive terminal. The terminals in a car battery are color-coded the same way.

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TinkerCAD Circuits Click the wire for the negative terminal and change the color to black.

Title Your Project Tinkercad provides random names for each new project. Click once on the name and rename the project.

Select the jumper wire joining the two halves of the board and change the color to red. Provide a descriptive name. I recommend the LED push button circuit. Click the Tinkercad logo next to the project name. This will return us to the main Circuits page.

Change the jumper wire connecting the LED and negative rail to black.

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Extending the Activity I like to include an activity where students have an opportunity to connect with something tangible. I will take out small boxes with an LED, switch, push button, battery, and resistor. I ask students to look at the components and discuss their impressions. Most students donâ&#x20AC;&#x2122;t realize the actual size of the components. Some will think they are larger than they thought. Others will think they are smaller than they thought. This is due partly to the large size of the components in the simulator.

Itâ&#x20AC;&#x2122;s important to include actual schematic circuits. There are various symbols that represent each of the components used in this circuit. The schematic shown in the image below uses symbols to represent the LED, resistor, push-button, and power supply.

Students use a sheet of paper to draw either the switch or push button circuit. They label each of the components on the drawing. Below the drawing, they write a short paragraph describing the circuit and the components. They are required to use the component names and academic language. My students usually keep a science journal. This journal can be a traditional notebook or a digital notebook. For the digital notebook, I use OneNote. Another option for a digital notebook is Google Keep. There is a drawing component in Keep. Students organize their notes with labels. As an independent project, I have students connect a regular light bulb to the circuit. They will include this circuit in their journal. They illustrate and annotate the diagram.

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Capacitors Weâ&#x20AC;&#x2122;re going to build on the skills we learned in the LED circuit. This circuit includes a capacitor. A capacitor stores current and releases it at a steady rate. The current in a circuit can change with power fluctuations. Power fluctuations can damage sensitive circuits. They are often used to smooth out the current supplied to components. They are also used to gradually reduce the amount of current being supplied to a component. A capacitor is a lot like a battery. It stores current and releases that current when a circuit is closed. They donâ&#x20AC;&#x2122;t store as much current like a battery. Capacitors are reliable and donâ&#x20AC;&#x2122;t need to be replaced like batteries. This is a good time to discuss potential energy and kinetic energy. Batteries and capacitors store electricity. This storage is potential energy. The stored energy is released into circuits and provides kinetic energy. The amount of kinetic energy released is measured as an electric current. The potential energy in batteries is measured in volts. The potential energy in capacitors is measured in Farads. Capacitors store electrostatic charge.

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Capacitor Circuit Create a new circuit project. Place a breadboard on the work area. Place a 9-volt battery next to the breadboard and connect the terminals to one end of the breadboard. Color code the jumper wires from the battery to the breadboard.

There are two types of capacitors available in the component panel. The capacitor available in the basic components panel is a ceramic capacitor. The capacitor we need is in the advanced components list. Click the components selector and choose All.

The capacitor is very large. It takes up a lot of space on the breadboard. We are going to work around it while setting up the rest of the components. Place the capacitor on the left side of the board for now.

Get a push button and place it on the right side of the board. Make sure it bridges the two halves of the breadboard.

Connect a jumper wire from the positive rail to the right lead on the button. Color code the jumper wire.

Select the polarized capacitor and take it over to the breadboard. This capacitor is a lot like a diode. It accepts current from one end of the component and passes it through to the other side.

Click once on the hole below the lead on the left side of the push button. Count four holes to the left and click on once on that hole.

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TinkerCAD Circuits This will create a connection between the row connected to the left lead on the push button and the selected row. This wire is necessary to accommodate the large capacitor.

Skip a hole and click once to start a new jumper wire. Connect this wire to the negative rail. We skipped a hole to accommodate the leads on the capacitor.

Get the capacitor from the left side of the breadboard. Place it so that the leads match the rows with our jumper wires. The jumper wires are hidden behind the capacitor.

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Place an LED on the breadboard. You will need to scroll down to the output section of the advanced components panel.

Place it a few spaces to the left of the capacitor. Make sure to place it on the same half of the breadboard occupied by the capacitor.

Click on one of the holes in the row connected to the positive lead of the capacitor. Run the jumper wire to the row connected to the Anode on the LED.

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TinkerCAD Circuits Connect another jumper wire from the row connected to the negative terminal on the capacitor and connect it to the Cathode row for the LED.

We need a resistor to prevent overloading our LED. We need some space for the resistor. Click and drag the LED to the top half of the breadboard. Leave a column empty for jumper wires.

Scroll back to the top of the advanced components panel. Get the resistor and connect it to the Anode lead on the LED. Place a jumper wire connection between the lower half of the breadboard and the Cathode row on the LED.

We need to make some adjustments to our capacitor to exaggerate the effects we are producing. Stop the simulation and click once on the capacitor.

Capacitors have different levels of capacitance. This is the amount of electrostatic charge a capacitor can hold. The capacitance is measured in Farads. The capacitor is currently set to emulate a capacitor with one microfarad. The little “u” symbol next to the letter “f” represents micro.

Stop the simulation and change the value from 1 to 100 microfarads. You need to stop the simulation each time a value is changed. You can change the value while the simulator is running but the results will still be based on the original value. Stopping and starting the simulator updates the values in the simulation. Start the simulation again and press the push button.

Press the Start Simulation button and press the push button. The LED lights up when we push the button. This isn’t any different from our first circuit.

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TinkerCAD Circuits The LED will light as before. The difference appears when we release the button. The LED dims gradually before it completely turns off. The LED is dimly light because the capacitor is still discharging current into the LED. It can’t store as much current like a battery, so the LED isn’t as bright.

We can increase the time the LED remains light by increasing the capacity of the capacitor. To really see the effect we need to increase the value by a lot. Change the value to 1,000. Don’t forget to stop and start the simulation. Press and release the button. The LED will remain light much longer. It will take about a minute to completely turn off.

Increasing the capacitance increased the amount needed to be filled before releasing the built-up charge.

Let’s take it one step further to really drive the point home. Increase the value to 20. Start the simulation and press the button. The LED doesn’t light up right away this time. It takes longer to fill the capacitor before it discharges. It takes about five seconds for the LED to begin glowing. Title the project Basic Capacitor Circuit and return to the main Tinkercad circuit page.

Let’s increase the value one more time to see what else is going on. Click the Farads unit selector and choose Farads. There are different units of measure. They are like using inches, feet, yards, and miles. Picofarads is the smallest. Farads is the main unit of measure. Change the capacitance value to 5 Farads. Run the simulation. The simulation shows the LED gradually going from dark to bright. The LED remains bright for much longer after we release the button. The LED gradually gets brighter because the Capacitor isn’t full yet. The capacitor needs to fill up with enough electrostatic charge before it is released.

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Extend the activity Students will illustrate the circuit. They will identify the different components. They will explain how the circuit works as current flows from one component to the other. Students will compare batteries and capacitors as sources of potential energy. Here are some things to think about when comparing the battery and capacitor. How does a battery store potential energy? How does a capacitor store potential energy? How does the storage of energy affect the reusability of batteries and capacitors? How are rechargeable batteries like capacitors? This is the circuit diagram of the project we just assembled. I have students draw and annotate this circuit in their journals too.

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Transistors Transistors and LEDs have revolutionized our modern world. Transistors have made fast and small computer possible. LEDs have made high-quality lightweight displays possible. All modern televisions and computer monitors use LEDs. In these lessons, we will learn to use the transistor as a switch. Transistors inside computers process lots of information. The transistor we will use here is much larger than the one used in the Central Processing Unit of a computer. This transistor is used to control components. Transistors have three leads. Each lead has a name and a purpose. The center lead is called the Base. The leads on either side are called the Collector and Emitter.

The location of the emitter and collector depend on the type of transistor being used. There are two types of transistors. Each transistor is referred to as either a PNP or NPN transistor. The difference in the type of transistor depends on how it is manufactured. They are both manufactured from three layers of semiconductor material. The materials are similar to those used in diodes. A transistor is a diode with an extra layer. The NPN transistor is the most popular and common. Each end of the transistor is made of a semiconductor material that is saturated with electrons. The center material is depleted of electrons. This positively charged layer is sandwiched between two negatively charged layers. This is the transistor we will use in our lesson. The PNP transistor is not as common. This transistor has a negatively charged layer sandwiched between two positively charged semiconductors.

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TinkerCAD Circuits For the transistor to work as a switch the base must receive electric current. The current stimulates the base to allow the flow of current across the collector and emitter. We typically have two power sources for a circuit with transistors. One power source activates the base and another provides power for a component. Our first project will have one power source. The first project will help us compare how the second project with two power sources differs and the advantages of having two power sources.

Switches

Use a jumper wire to connect the resistor to the Anode on the LED.

Get a 9-volt battery and attach jumper wires to the top half of the board.

For this project, we will need a breadboard, LED, resistors, button, and transistor. Create a new project. Place a small breadboard onto the work area. The first step is familiar. Attach a resistor to the board. One end connects to the positive rail. Add the LED so the Anode is on the same connection as the resistor. We are using the lower half of the board too. Run jumper wires from each rail in the top half of the board to the lower half.

This circuit is going to have a few more components that our other circuits. I want to have plenty of room to keep things easy to see. Move the LED to the other half of the breadboard. Place it on the bottom of the board.

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Digital Maestro Magazine - Alex Reyes

TinkerCAD Circuits In the first circuit we created, we placed a push button between the Cathode and the negative rail. We are going to do the same thing here but we will use a transistor as our button to close the circuit. Find an NPN transistor in the components panel. It’s in the basic set of components.

Circuits run in loops. To complete the loop in this circuit we need to connect a jumper wire from the emitter to the negative rail. The transistor is large like the capacitor in our previous lesson. Instead of moving the transistor to attach a jumper wire we will attach it to the bottom of the board. The circuit is almost complete. We don’t have a complete connection yet. Press the Start Simulation button. The LED doesn’t light because we don’t have a closed circuit. We need to pass current into the Base of the transistor to close the circuit.

Place the transistor in the top half of the board next to the LED. A transistor has three parts. It has a collector, base, and emitter. The transistor on our board has the letters C, B, and E to help identify the parts. When thinking of the transistor as a switch it is helpful to see the Base as the button that is pressed or activated with a current. Let’s take a moment to see how this circuit resembles a previous circuit. If we replace the transistor with a switch it looks like one of our previous lessons.

Connect a jumper wire from the Cathode on the LED to the Collector on the transistor.

This is the part that makes it all work. Connect a resistor to the Base of the transistor. The resistor will connect with the lower half of the board. Connect a jumper wire from the other end of the resistor to the positive rail.

Digital Maestro Magazine - Alex Reyes

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TinkerCAD Circuits The current running from the positive rail through the resistor and base of the transistor is what activates the transistor switch.

Press the Play Simulator button. The LED will light.

This basic transistor circuit uses one power source to activate the transistor and light the LED. Let’s take a look at a circuit where we use a smaller current to pass a larger current to a circuit.

Amplification The circuit for this lesson is similar to the one in the previous lesson. We don’t need to recreate the whole project. We will be using many of the same components. The current flowing into the base of the transistor is what causes the transistor to close the circuit. At this point we have a discussion noting the similarities and differences between a transistor, push-button, and switch. We discuss how the transistor is like a push-button and how it is like a switch.

We’ll make a copy of the previous circuit and use it for the next. Hover your mouse arrow over the circuit preview of the previous project. Click the gear icon that appears in the upper right corner.

Students have discussions in small groups. They discuss when a transistor as a switch would serve better over a regular switch. What are the advantages and disadvantages of using a transistor as a switch in a simple circuit?

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Digital Maestro Magazine - Alex Reyes

TinkerCAD Circuits Select the Duplicate option.

A copy of the circuit will be created and opened. The first thing we are going to do is replace the 9-volt battery with a AA battery. Click once on the 9-volt battery and press the delete key on your keyboard. Find a 1.5 volt AA battery and place it next to the board.

We reduced the voltage of the battery. In doing so we reduced the amount of current going to the circuit. Press the Start Simulation button to see the result on the LED.

The terminals on the battery are at a right angle to those on the breadboard. I like to rotate the battery so the terminals are parallel. Stop the simulator and get another 1.5 volt AA battery. Place this battery on the opposite side of the board. Rotate the battery. Connect one jumper wire to the negative rail at the top of the board. Connect another jumper wire to the positive rail at the bottom of the board. This battery will serve as the source for the Base of the transistor. It will trigger the switch to allow current to flow through the transistor and circuit. There is a rotate button in the button bar next to the trashcan icon. Clicking the button will rotate a component clockwise. Make sure the AA battery is selected and click the rotate button once or twice. We need to do a lot of clicking to rotate the battery in this direction. Hold the Shift key on your keyboard when clicking the rotate button to rotate counter-clockwise. Connect the terminals to the board with jumper wires. The terminals donâ&#x20AC;&#x2122;t align so the wires will cross. This is where color coding really helps.

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TinkerCAD Circuits This battery provides the power source for the transistor base. We donâ&#x20AC;&#x2122;t need the power from the other battery. Remove the jumper wire connecting the battery on the right side of the board. Leave the wire for the negative connection. We still need a ground connection for the emitter.

Click the Start Simulation button. The LED is much brighter now.

Click once on the battery on the left side. Go to the configuration panel for the battery and change the built-in switch option from No to Yes.

We want the LED to shine brighter. Click once on the 1.5 volt AA battery on the right side of the board. The configuration panel for the battery shows a count of one battery.

Click the battery count selector and choose 4 batteries.

The battery will be enclosed in a case with an ON/OFF switch. Click once on the switch to turn the battery current OFF. This battery supplies current to the transistor. When current from this battery stops, the current to the transistor stops. This opens the circuit and prevents current from batteries on the other side from powering the LED.

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Digital Maestro Magazine - Alex Reyes

Extending the Activity Extending this activity is like other activities. Students will illustrate the circuit and label the components. They will also illustrate the flow of current through the circuit. They will illustrate the flow of current flowing from each battery into the transistor. They will write a brief description of what the circuit is doing. Students will write a brief paragraph describing what the transistor is doing as a switch in the circuit. They will compare the transistor as a switch with a regular switch. The image below is a circuit diagram of the project we just assembled.

Digital Maestro Magazine - Alex Reyes

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Digital Maestro Magazine

TinkerCAD Circuits: Teach basic electronics with fundamental circuits

This issue reviews the assembly of a basic circuit with an LED and push button. We compare the use of a push button and a switch in the same...

TinkerCAD Circuits: Teach basic electronics with fundamental circuits

This issue reviews the assembly of a basic circuit with an LED and push button. We compare the use of a push button and a switch in the same...