# Electronics learning for hobbyists and students

Learning electronics tutorials for beginners is the primary goal of this site.

Quickly familiarize yourself with the following topics. They will make more sense as you learn about more circuits.

This page is constantly being updated as I try to make it easier to understand. Some topics may be covered twice until I remove the less desirable version.

## Some important terminology:

• Voltage: Electric potential. Unit: Volt. Symbol: V
• Current: Electric charge flow. Unit: Amp (usually milliamps in basic electronics). 0.001A is the same as 1mA. Symbol: I
• Resistance: Opposition to current from a voltage. Unit: ohm. Symbol: Ω (Greek letter omega). Very often resistance is in the thousands of ohms (kilohms/kΩ).
• Semi conductor: Conductivity depends on certain factors specific to that particular component.
• Ohms law: Mathematical formulas  used to calculate the relationship between voltage, resistance and current. Formulas: I = V/R     V = IR     R = V/I
• Power: Work done (heat and/or light generated, motor speed, etc,): Unit: Watt. Symbol: P Formula: P = VI
• Ground: There needs to be a difference in voltage between 2 points in order for the possibility of current to flow. Usually the negative side of a supply is declared to be the zero volt reference point ground. The positive side of the power supply is the voltage difference from zero volts. A 1.5V battery positive terminal is +1.5V in relationship to ground, while a 9V battery positive terminal is +9V in relationship to ground. Many circuits have multiple power supplies with different voltages, and all their negative terminals are connected directly together so that they share the same 0 volt reference point voltage (simply called ground).

This site is going to keep the movement of electricity simple.  You need to be familiar with the terms below. Usually you will imagine the movement of electricity as conventional current due to the universally established way we build circuits to this day, even though it was discovered that electron flow is what is truly happening.

• Conventional current (or just current) : Early scientists could tell that electricity involved something either being pumped and flowing through entire electrical circuits, or shifting from one point to another (static electricity). Not knowing exactly what was going on, it was assumed that electricity flowed from more positive to more negative and thus circuit schematics were designed to look like positive moving charges were starting at the positive side of the power supply, and are moved through the circuit to the negative side of the power supply. This is how you will learn about electronics when studying the design of circuits.
• Electron flow: Relatively recently in the study of electricity, it was found that atoms have negatively charged electrons. A battery actually moves electrons through it, out of the negative side, through any load attached across the battery, and back into the positive side of the battery in an endless cycle. Electrons are continuously shifting from one atom to another as long as there is conduction. This is how you will learn about electronics when studying the physics and chemistry of atoms.

### Resistor component basics

The resistor component’s schematic symbol is a jagged line (or less commonly, a rectangle) and most resistors are rated for a maximum of 1/4W (0.25) . They resistor component most commonly looks like (package) a rounded off cylinder with a slightly narrower middle and colored bands to indicate their value plus the tolerance, which is the percentage higher or lower the actual resistance may vary from the rated value.

To know how to read the colored bands, you have to become familiar with the resistor color code. Resistor color code

### Current through a 1,000Ω (1k) resistor examples

Remember, ohms law is calculated in Volts, Amps, and Ohms. The more commonly express milliamps and kilohms must be converted to Amps and Ohms before calculating.

If there is one volt across a 1,000 ohm resistor, then 1V/1000Ω = 0.001A will flow through the resistor.  However, that current is usually expressed as being one milliamp (1mA) instead of 0.001A.

5V across a 1,000 ohm resistor, also called a 1k resistor, will pass 5mA though the resistor.

Keep in mind that very few electronic components or circuits have a high level of precision, and none are perfect (Ideal). Numbers that are given or calculated are almost always just close approximations to the actual value which is usually perfectly fine as long as you err on the side of caution.

# Simple circuit: Low voltage lightbulb

The incandescent light bulb is a nice component to look at first. They are a specially made resistance based component that does something useful (emits light) when enough current is passed through it. You just have to apply the right voltage to it and it lights up. Too low of a voltage and it won’t like up much if at all, and too high of a voltage and the light bulb will burn out early.

### Higher voltage incandescent lightbulbs explained:

For informational purposes only. Don’t build higher voltage circuits as they are dangerous. Only use high quality commercially made products as recommended by the manufacturer.

If you are familiar with household incandescent light bulbs…. (they are less common these days as they are being replaced by more energy efficient bulbs.)

• In the US, household incandescent light bulbs are made to work with 120V alternating current (AC).
• A 120W incandescent light bulb made for 120VAC will have 120Ω (ohms) of resistance and pass 1A of current while it is on. A couple power formula variations: 120V x 1A = 120W    0r    120W/120V = 1A
• Alternative types of 120VAC lightbulbs are commonly being used these days. Their wattage rating is usually much lower than incandescent light bulbs even if they emit as much light (because they get less hot), and that is why they are more energy efficient.

## Learning electronics topics and pages:

The vast majority of the time, electronic circuits are taught with schematic diagrams using schematic symbols for components. Above is a quick sample of schematic symbols, and below is the typical appearance of some of the most common components.

Through hole means that there are metal wire leads (pronounced like “leeds”) that can be inserted in holes. Surface mount components have metal areas that can be soldered directly to a surface of something, and are not covered on this site.

### More current through a resistor examples:

The current will be the same through the resistor whether it also goes through a meter measuring current, or if it goes directly back to the voltage source (battery in this diagram).

9V/1,000Ω = 0.009A (9mA)

Putting a voltage directly across a resistor is the easiest circuit to calculate how much current is flowing by using the Ohm*s law I = V/R .  https://electronzap.com/current-through-a-resistor-learning-electronics-lesson-0001/ .

Current through an LED protected by a resistor from a voltage:

Again, current will be the same whether you connect the battery to resistor, resistor to LED and LED to battery, or if you open up one of those connections and insert a current measuring meter as shown in the diagram.

Forward biased (FB) diodes/LEDs drop some voltage from reaching the current setting resistor. Red LEDs drop about 2V while forward biased. Therefore a 9V battery, with 2V dropped from the resistor, will mean there is 7V across the resistor, which sets the current through all the components in the circuit above. 7V/1,000Ω = 0/007A (7mA)

When forward biased (diode wired to conduct easily), the long lead (Anode) of an untrimmed indicator LED needs to head to the positive side of the battery, while the shorter lead (if untrimmed) cathode lead needs to head to the negative side of the battery to light up.

Page covering the diagram above https://electronzap.com/current-through-an-led-circuit-learning-electronics-lesson-0002/ for those who want these topics covered more quickly.

Incandescent light bulbs are relatively rare now as LEDs have mostly taken their place. While studying basic electronics, you will study a lot of circuits with 3 – 5mm indicator LEDs that need to be protected by a resistor. Incandescent light bulbs are resistors that are specially made to get hot enough to emit visible light. Light bulbs don’t need another component to protect them as long as you don’t apply a voltage higher than what they are rated for.

Pay attention to how every component and connection in a lot of simple circuits are connected end to end (series). The same amount of electric current flows has to flow through the entire series circuit at the same time. If you disconnect any part of a series circuit, there will be no current flow.

Voltage:

Voltage is the energy that moves electric charges (current) through a circuit. The load needs enough resistance/voltage drop to safely limit how much current flows.

Most electronics projects these days are powered with variable voltage and maximum current power supplies instead of batteries. You simply set the voltage to what you want for the circuit, and it is a good idea to set the power supply to only output no more current than could damage any of the components as long as the total circuit doesn’t require more than that much current.

You can’t see voltage or current, so it is important to know how to measure them. Measuring current is done differently than measuring voltage. I show how to measure current further down this list of topics.

Resistance (R) based components limit the current (I) that flows through them based on the voltage (V) across them and their resistance. This is calculated using the Ohms law for current I=V/R .

Series (connected end to end electrically) components all pass the same amount of current. So if you know the current through any of them, then you know the current through all of them.

LEDs are a type of diode (current flows through one direction but not the other). They light up when current flows through them while forward biased (anode more positive than cathode) , and are therefore a simple way to have a visual for when current is flowing.

Make sure to limit current through an LED with a resistor, as is covered in the LED circuit link below. Also, being a diode, if you connect them reverse biased (cathode more positive than anode), then they will block current and not light up.

Lots of beginner circuits include an LED. It is important to know how to protect the LED with a resistor.

While designing your own circuits, you will need to know how hot resistors (and other components) will get. The power (P), aka. heat generation, of a resistance based component is the voltage (V) across it times the current (I)  flowing through it P =VI  . Most resistors are 1/4Watt (0.25W) but should be kept under 1/8W (0.125W).

555 timer is an integrated circuit (IC). Being an IC, it has complex circuitry combined in a single package with external pins/terminals to connect to other circuitry. You can easily make all kinds of fun circuits with just a 555 timer and the components covered above, so I think it’s a good component to learn next.

Transistors will probably be the most challenging components to learn. Understanding them will help you understand all of electronics much better, and help you the most in being creative while designing your own circuits.

Other topics:

These pages are still being compiled.

### Always use datasheets to research components:

When you start using components with part numbers, make sure to do a google search for their datasheet. Information on this site is not guaranteed to be accurate. Always verify any electronics information you get by checking the manufacturer’s datasheet.

Unfortunately datasheet aren’t the easiest documents to understand. I am working on explaining how to make reading them easier.

###### List of Electronics topics:

There’s an almost endless number of exciting electronics topics that can be studied. Below is many of them. I plan to make a page for as many of them as possible. You should always do google searches of any topics that sound exciting.