Learn More About Your MicroKits

     Looking for more information after building your kit? Here's all the info we couldn't fit in our booklets. These topics cover many different concepts, so don't worry if you don't understand it all at once. Use this as a starting point as you begin learning more about electronics!

     Something unclear? Want more information on a topic? Want to use these resources in your class? Please email me at dave@microkits.net. It's always great to talk to MicroKits builders!

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Part 1

All About Theremins

What's a Theremin?

RCA Theremin

     In 1920, electrical engineer Leon Theremin discovered something. The closer he moved his hand towards the circuit he was working on, the more it reacted. As a cello player, he realized that he could use this phenomenon to make a musical instrument. His new invention had a vertical and a horizontal antenna. Moving his right hand towards the vertical antenna increased pitch. Meanwhile, moving his left hand towards the horizontal antenna decreased volume. With this setup, he could create music just by moving his hands in the air, with no physical contact. This invention wowed onlookers with its ghostly operation and ghostly sounds.

MicroKits Theremin

     The theremin was one of the first electronic musical instruments. For decades, it has inspired musicians and engineers to create new sounds and new instruments. We continue that tradition with the MicroKits Theremin Kit. We've designed a version of the theremin that anyone can build, including you! What sounds will you discover?

Intro to Electric Fields

Rubbing Wool

     Theremins use capacitance to sense the world around them. Capacitance is the measure of how easy it is to store energy between two objects in the form of electric fields. You’ve interacted with electric fields if you’ve ever felt static electricity from a nearby object. If you rub a balloon on wool, it creates a negative charge on the balloon and an equal positive charge on the wool.

Far Capacitance

     When you move the two objects far apart, they are still charged. But because of the distance, electric attraction is weak. From far apart, the wool and balloon barely interact.

Close Capacitance

     But move the wool close to the balloon, and the two objects will attract each other. They have the same amount of charge as before, but the attraction is stronger. This is because there is more capacitance between the objects. When two charged objects move closer together, it is easier for electric fields to form between them.

Small Capacitance

     Capacitance also depends on the size of an object. If an object is half the width, only half of the electric fields will form, halving capacitance. The exact shape of the two objects and the material between the two objects also affect capacitance.

How a Theremin Works

Theremin Sensing Environment

     The theremin works using the same electric fields formed from static electricity. But instead of charge staying the same, it changes. A Theremin's circuitry adds charge to the antenna at a fixed rate. This charge is used to measure the capacitance between the theremin and the nearby environment.

Far away Capacitance

     With only a little bit of capacitance to the outside world, few electric fields form, and the voltage on the antenna increases quickly.

Theremin Sensing Close

     But if you move your hand towards the antenna, capacitance increases. Your hand becomes a place that electric fields can build up. Because the circuit adds charge to the antenna at a fixed rate, it takes longer for the voltage on the antenna to rise. The theremin detects this change in charging time and uses it to control the pitch and volume of the output. 

     Think of capacitance as a water balloon, and the charge building up as a constant flow of water. Your hand adds capacitance, or makes the balloon bigger. Because of this, it will take longer for the tank to fill up. We will use the idea of electricity flowing like water to explain electronics in more details in the next section.

 

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Part 2

Meet the Basic Parts

Electricity as Water

     When engineers talk about electricity, they are actually talking about two things: voltage and current. To understand the difference, let’s pretend a circuit is made out of pipes holding water. We will replace electrons, the particles that carry electrical charge, with drops of water.  

Electricity as Water

     Voltage measures how much “water pressure” there is between two points in a circuit. The higher the water level, the more potential energy the water has. This is similar to how a battery gives electrons potential energy. Voltage is measured in Volts (V).

     Current measures how much “water flow” there is through an area. The higher the current, the more electric charge moves in a direction. Current is measured in Amps (A) and charge is measured in Coulombs (Q). If a wire has one amp of current, it means one coulomb of charge is flowing through it every second.

Low Voltage

     Voltage and current are related to each other. Just like low water pressure causes water to flow slowly, low voltage will cause a low current. Different electrical parts change how voltage and current interact.

What's a Battery?

Battery

     Batteries act like water tanks. Water tanks are placed on towers or on top of hills to increase water pressure, allowing water to flow. And batteries use electrochemistry to create a voltage, allowing electrical current to flow through a circuit. In our kits, batteries are stored within battery boxes like the one shown above.

Battery Loop

     Batteries have a positive and negative side. On this battery box, the black wire is negative and the red wire is positive. The positive wire connects to power, the highest voltage part of the circuit. The negative wire connects to ground, the lowest voltage part of the circuit.

     Current flows from the positive side of the battery through the circuit and back through the negative side. Current then flows into the battery. As it travels through the battery, the current is boosted and picks up voltage. With voltage renewed, the current has the power to flow into the circuit again. This is why a circuit is called a "circuit", for the circular path current takes over and over again.

What's a Breadboard?

     When electronics are made in a factory, they are made using printed circuit boards. But this requires high heat and special tools, so engineers often use breadboards. Breadboarding makes it easy to place and replace parts. Circuit designers use breadboards to quickly build circuits and experiment, and with our kit, you can too!

Breadboard

     At first, breadboarding meant fixing parts to actual wooden breadboards. But modern breadboards are made of durable plastic with electrical conductors built inside.

Breadboard Grid

     Breadboards have a grid of points where wires or parts can be inserted. Points on the same row of the grid connect horizontally, but not across the middle. On each side of the grid are a pair of strips, marked “+” Positive and “-” Negative. These strips connect vertically and deliver power across the circuit.

Power Bridge

     MicroKits manufactures a “power bridge” which connects the power strips on each side together. This makes it easy to connect batteries to the breadboard. The battery negative terminal connects to the “-” on both sides of the breadboard, and the battery positive terminal connects to the "+".

Breadboard Connections

     Let’s make a simple circuit to show how breadboards work. Connect a resistor between Row 10 and Row 13. Then connect an LED between positive and Row 10. Finally, connect a wire from Row 13 to negative. When a battery is connected to the power strip, the LED will turn on. Electricity flows from the positive strip to the LED to Row 10, then through the resistor to Row 13. Finally, it returns to negative through the yellow wire. Breadboards make it easy to combine parts to make a circuit!

What's a Resistor?

Water Resistance

     The most basic electrical part is the resistor. It restricts the flow of electricity. Just like a long narrow pipe will only let some water flow, a resistor will only let a certain amount of current flow for a given voltage. 

Resistor

     Inside resistors, electricity flows through a narrow thin film. The same way a long or narrow pipe restricts the flow of water, this film makes it difficult for electrons to travel. The longer or narrower the film inside the resistor, the more resistance.Ohms Law

     Resistance is measured in ohms: One volt is needed to create one amp of current through a one ohm resistor. Decreasing the resistance but keeping the voltage the same will increase the current. Keeping the resistance the same but increasing the voltage will increase the current.

     Voltage (V) equals Current (I) times Resistance (R). This relationship between resistance, voltage, and current is called Ohm’s Law. There are three different ways to write Ohm’s Law depending on what you want to calculate.

     You can use Ohm's Law to find how much voltage you will need to create a certain amount of current flow through a given resistance. Multiply the current and resistance to find the voltage.

     Need to know how much current will flow through a resistor at a voltage? Divide voltage by resistance.

     Need to pick a resistor that will create the right amount of current at a given voltage? Divide voltage by current to find how much resistance your resistor needs.

Resistor Color Code

     The color bands around resistors are a code. Each color represents a number, and decoding them shows how many ohms the resistor has. The first two bands are the two biggest digits, and the third band shows the number of zeros that follow. The fourth golden band shows that the resistor has a tolerance, or accuracy, of 5%. Digikey has an online calculator for resistor color codes that you can visit by clicking here.

What's a Capacitor?

Capacitor Filling

     A capacitor works like a “water balloon” connected to a water pipe. It stores up charge when a voltage is applied, the same way a balloon stores water under pressure.

Capacitor Full

     A water balloon stops filling when the pressure in the balloon equals the pressure in the pipe. And current flows into a capacitor until the voltage inside the capacitor equals the voltage it connects to.

Capacitor

     Inside a capacitor are two plates. These plates do not touch but are very close together. When voltage is applied, an electric field builds up between the plates. More charge builds up when the plates are larger or placed closer together, increasing capacitance.

Capacitance Math

     A bigger water balloon will store more water before it starts to push back, and a bigger capacitor will store more charge before voltage rises. Capacitance (C) is equal to the amount of charge (Q) stored per volt (V). This is like how a balloon’s capacity could be defined as the amount of water it can store for a given pressure. Capacitance is measured in farads, but common capacitors have values of nanofarads or picofarads. Nano means one billionth and pico means one trillionth. A 100 nanofarad capacitor would store 100 billionths of a coulomb of charge at one volt.

Capacitor Code

          Capacitors usually have a three digit number printed on them. Like with resistors, the third digit is how many zeros follow the first two digits. The code “104” means 10 followed by four zeros, or 100,000. This code is in units of picofarads, and 1000 picofarads is equal to 1 nanofarad. 100,000 divided by 1000 is 100, so we know this capacitor is 100 nanofarads.

What's a Speaker?

Transducer

     Speakers turn electricity into sound waves you can hear using magnetic fields. A speaker is a transducer; it transduces electricity into air waves you can hear. When current flows into the speaker in one direction, it pulls air in. When current flows in the other direction, it pushes air away. If the speaker receives 260 electrical pulses in a second, it will vibrate the air at the same rate. This creates a sound with about the pitch of middle C, the middle key on a keyboard.

Speaker Inside

     Inside the speaker is a coil and a permanent magnet. The coil creates a temporary magnetic field only when current runs through it. When current is reversed, the coil's magnetic field is also reversed. The permanent magnet creates a constant magnetic field.

     When current flows one way through a coil, the magnet and coil magnetically attract, and the coil pulls towards the magnet. When current is reversed, the coil pushes away from the magnet. This coil is attached to a cone. When the coil moves, it moves the cone and pushes and pulls nearby air. Thus, the speaker transduces electrical current into moving air.

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Part 3

Meet the Semiconductor Parts

What's an LED?

LED

     LEDs, or Light Emitting Diodes, turn electrical current into light. They can create light in many different colors, including colors our eye can't see. The more current an LED takes, the more light it creates.

LED Semiconductor

     Inside an LED are two types of crystals, called N type and P type semiconductors. N types have a crystal structure with extra electrons, and P types have "electron holes", places in their crystal where electrons can fit. Usually, electrons can only flow from the N type to the P type. A diode is made by placing an N and P type semiconductor together.

     When an electrons jump from the negative N type semiconductor to the positive P type semiconductor, it lets off a fixed amount of energy. This fixed amount of energy is emitted from the LED as a photon, a particle of light. The LED in our theremin kit creates green light.

     Because the electron needs a certain amount of energy to jump from the N to P type semiconductor, LEDs need a certain amount of voltage to turn on. At low voltages, no or almost no light is created. But when the LED reaches its threshold voltage, it lights brightly. A small increase in voltage creates an exponential increase in current flowing and light created.

Simple LED Circuit

     To keep the LED from burning itself out, a current limiting resistor is used. By itself, the LED would draw exponentially more current from a small increase in voltage. But because the current that goes through the LED also goes through the resistor, the total current is reduced.

     An LED’s threshold voltage depends on what color it is designed to emit. A green LED might need 2.1 volts. But because blue photons have more energy, blue LEDs need 3 volts. LEDs only work when current flows in the correct direction. If you install an LED backwards, it won’t turn on.

What's a Transistor?

Transistor

     A bipolar junction transistor (BJT) is a three pin electrical part used to turn a small current into a much larger current. A transistor has three pins: base, emitter, and collector. A small current into the base creates a large current into the collector. Even regular transistors can amplify current 50 or 100 times.

NPN Semiconductor

     Transistors are made from semiconductors, just like LEDs and other diodes. But instead of one N type and one P type semiconductor, transistors are a semiconductor sandwich. NPN transistors are two N types with a P type in the middle, and PNP are the opposite.

     If you power the collector but not the base, no current will flow through a transistor. But by sending a small amount of current from the base to the emitter, a much larger current from the collector to the emitter can flow. A small base current removes the "obstacles" inside the semiconductor, allowing a much larger collector current to flow.  

Transistor Circuit

     Transistors are useful when you want to turn a small signal into a large signal. In the above circuit, a large resistor feeds a small current into the base of an NPN transistor. The transistor multiplies this current into the collector. This collector current is enough to light up the LED. Transistors are useful when you need to amplify a small signal from a sensor or send power to speakers or motors.

What are Integrated Circuits?

Integrated Circuits

     An integrated circuit, or IC, is many transistors packed into a single part. The transistors inside an IC create subcircuits, and when the IC is connected to external parts, a complete circuit is made. This allows engineers to create complex circuits with only a few parts. Integrated circuits have pins for power, ground, inputs, and outputs. Integrated circuits come in all kinds of packaging but are usually encased in a black epoxy rectangle with pins to the side or underneath.

     There are hundreds of thousands of different ICs, all with different functions and specifications. Some are used to manage power, others amplify signals. One of the best ways to learn more about electronics, beginner or expert, is to read the datasheets of different ICs. Datasheets will show what the IC does, what parts it needs to connect to, and the theory behind how it works.  You can see all the integrated circuits available on Digikey by clicking here

Tick the 555 Timer

Tick with Pins

     Tick from our MicroKits Theremin Kit is a type of integrated circuit known as a 555. The 555 IC is like an adjustable clock. By combining the 555 with a few external parts, we can create a circuit that switches between a low and high output. Connecting different resistors and capacitors changes how quickly the clock ticks. That’s why we’ve given this chip the nickname “Tick” in our kits!

     Tick is technically a “556” timer, which just means they have two 555 timers built in, one on each side. 555 timer chips can be used in many different kinds of circuits. You can read the 555's datasheet by clicking here: https://www.ti.com/lit/ds/symlink/tlc556m.pdf.

Resistor Capacitor Circuit

     555 timers work using the principle of resistor-capacitor charging, often called RC charging. If you charge up a capacitor through a resistor, current will be restricted, and the capacitor will charge in a slow, predictable way.

     555 timers constantly charge and discharge a capacitor through a resistor. The larger the capacitor or resistor, the longer it will take the timer to complete a cycle.

Tick the Cap Sensor

     When you move your hand towards a MicroKits theremin, you increase capacitance and increase the time it takes Tick to create an electrical pulse. The higher the capacitance, the fewer pulses happen every second. Tick converts capacitance into a useful signal that Micro, the other chip in our theremin kit, can process.

Micro the Microprocessor

Micro with Pins

     Micro from our MicroKits Theremin Kit is a type of integrated circuit known as a microprocessor. Micro has 8 pins. One pin takes in power, and one other connects to ground. The other pins do different things depending on the code stored inside Micro. For our theremin kit, we wrote code that tells Micro to have two inputs and two outputs.

Micro Thinking

     Inside Micro are three subsystems: a way to send and receive data from the outside world, a way to store code, and a way to process information. Micro combines what is stored in their memory with what they measure from the outside world. How Micro reacts to the signals they receive depends on what code they are running.

Micro Signals

     In the MicroKits theremin, Micro receives two signals from Tick. By counting how often pulses arrive on the volume and pitch signals, Micro knows how long it takes Tick to charge the volume and pitch antenna. Using code, Micro converts these signals into a musical output signal. This signal is sent to the speaker, after being amplified by a transistor.  

     Microprocessors are like tiny, simple computers. While a computer connects to many gadgets and does many things at once, Micro only connects to Tick and the speaker, and has only one job. But Micro does a great job!