Electronics

Units

Voltage

Voltage is the difference in electric potential between two points. One point has a surplus of electrons, the other one a lack of electrons. A surplus of electrons is called negative charge (-), a lack of electrons positive charge (+). They are also called poles.

Voltage is measured in V (Volt) and denoted by U.

Current

Current flows when two opposite charged poles are connected with a conducting material. In some cases, when the electric field is strong enough to ionise a medium and make it conductive, current can flow through a usually non conductive material. That is what happens with air when a lightning occurs.

Current is measured in A (Ampere) and denoted by I.

Resistance

The resistance of materials against current flow.

Measured in Ω (Ohm) and denoted by R.

Capacitance

Capacitance is the ability of a conductor to store electric charge.

Measured in F (Farad) and denoted by C.

Inductance

The tendency of an electrical conductor to oppose a change in the electric current flowing through it. When current flow changes, the magnetic field around a conductor also changes. This change induces a voltage in the conductor that counteracts the current flow.

Measured in h (Henry) and denoted by L.

Theory

Ohm's Law

Ohm's law show the correlation of voltage, current and resistance and can be used to calculate the correct resistor for an LED.

$$ R = \frac{U}{I} $$

U = R × I

LED example

Assume we have a circuit with 5V VCC and want to use a red LED in it.

Electrical characteristics of a typical red LED that are interesting for the example:

• Forward Current: 20mA (20 milliamps)
• Forward Voltage: 2.0V (2 Volts)

$$ R = \frac{U_{ges} - U_{led}}{I} $$

$$ R = \frac{5V - 2V}{0,02A} = 150 \ohm $$

Circuit

An electronic circuit is a closed loop of conducting material that leads from one pole of a voltage source to the other pole.

$$ \begin{circuitikz} \draw (0,0) to[battery] (0,4) -- (4,4) to[lamp] (4,0) -- (0,0) ; \end{circuitikz} $$

A very basic example of a lamp connected to a battery.

Common Components

Voltage Sources

Voltage sources can be batteries, bench power supplies, solar cells and many more.

Resistors

Resistors are used to limit the current flow in a circuit. They are needed to limit the current for LEDs for example.

Capacitors

Capacitors store a certain amount of electrical charge. They are used to buffer voltage in a circuit and can smooth out a dirty voltage source. They have many more uses of course.

Transistors

Transistors are the basis of our modern computerized lifestyle. They are basically an electronic switch. The new Apple M1 Max accomodates 57,000,000,000 transistors.

Diodes

Diodes allow current to flow in one direction only.

LEDs

Light emitting diodes are a special type of diode that emits light when current flows through it. They come in many colors, sizes and packages.

Microcontrollers

Arduino

Arduino is a project that was founded many years ago to make working with microcontrollers easier. It started by offering a breakout board of an atmega16 with an integrated USB connection. Arduino also made an IDE available to be able to easily program the Arduino boards.