An Introduction to Circuits, Components and Electricity!

What is a Breadboard, and Where’s all the Bread?

In electronics, a breadboard actually doesn’t involve any bread at all! It’s a platform that allows for electrical connections to be easily made. It provides a way for electrical components such as resistors, capacitors, and transistors to communicate and interact with one another. (Don’t worry if you don’t know what those are, we will talk about those components later!) Breadboards are commonly used for experimenting with circuits which we will be doing today! :D

In the picture above, you can see how each of the holes on the breadboard are connected to one another. This is very important once we start to make our own circuits!

The Battery and the Battery Snap! “With great power comes great responsibility!”

The battery is what provides power to the circuit. It is the component that gives all of the other components energy or voltage for them to communicate and interact with one another.

Today, we will be using a 9 volt (9V) battery. The battery snap…well…snaps onto the battery and allows it to be easily hooked up to the

breadboard as shown below.

The red wire coming off of the battery snap is called the positive lead while the black wire is called the negative lead. The leads on the battery snap simply extend the positive and negative

leads of the battery. One of the battery’s leads is normally labeled on it so you know which lead is which just in case you forget!

In the picture below, the positive lead is labeled.

*Important!*: Never make a direct connection between the positive and negative leads of a battery. It can permanently damage it and start a fire!

Wires, Wires, Wires!

Wires are used to help make connections between components and between unconnected rows in breadboards as shown in the picture below:

Wires are made out of metal which is highly conductive. This means that very, very, very, very small, negatively charged particles called electrons are able to easily flow through them, kind of like how water is able to easily flow through pipes! Flowing electrons or charge in a circuit is called a current, just like flowing water in a river!

The Light Emitting Diode (LED)“Let there be light!”

When charge moves through the LED, it lights up! In addition to giving of (or emitting) light, this component is also a diode! This means that it only allows charge (or electrons) to flow one way through it! Components with this property are said to be polarized. If you look at the picture above, you will see that the LED has one lead longer than the other. The longer lead is the positive lead, while the other is the negative lead. Electrons can only move from the negative lead to the positive lead. Otherwise, if you try to get the charge to flow the other way, either nothing will happen, or you could burn out the part!

The Resistor“Join the resistance!”

This component reduces the speed at which electrons move through the circuit. Without the resistor, charge would move so quickly through components that they would burn out! A resistor protects these components (like LEDs) by slowing down the current that flows into them. Not all resistors are the same though! Some are more resistant than others. Each resistor has different colored bands on them to help tell us how resistant they are to current flow. The greater the resistance, the slower the current flow will be!

Now, if we put everything together so far, we can get a…

Simple LED Circuit:

What is going on in this circuit?

The electrons that come from the battery first flow through the resistor where they get slowed down. The wire then acts as a bridge, allowing those electrons to move from the resistor to the negative lead of the LED. Next, the charge flows through the LED, lighting it up! Finally the electrons come out of the LED’s positive lead and go back to the battery.

Before we get into the next circuit, we have to introduce another component…

The Potentiometer!“The potenta-what now?”

The name “potentiometer” is just a fancy way of saying “a variable resistor”! So far, the resistors we have talked about have had a constant resistance. However, for potentiometers, YOU can change its resistance by turning the grey screw clockwise or counterclockwise with a Phillips screwdriver! While potentiometers do have three pins, we will most likely only be using pins 1 and 2.

*Important!*: Be careful to not force the movement of the screw! The potentiometer’s resistance can only be changed by so much!

Now that we know what a potentiometer is, let’s move on to something a little more interesting!

Basic LED Dimmer Circuit:

For this circuit, we pretty much have two simple LED circuits in one, however, one of them has a potentiometer hooked up between a resistor and an LED. Depending on which way you turn the potentiometer’s screw, the one LED will either get brighter or dimmer. When you increase the potentiometer’s resistance, it is able to dissipate more energy from the battery so that less energy is able to get to the LED making it dimmer! However, if you decreased the potentiometer’s resistance, more energy is able to get to the LED which would make it brighter! This circuit is used as a basis for the dimmer switches that you may have in your house!

Why does changing the potentiometer’s resistance not have an effect on the brightness of the other LED? The way things are hooked up, the two LED circuits are in parallel with one another, meaning that the current from the battery is split between the two LED circuits. Now, the potentiometer can only influence the charge that moves through it, and in this setup, all of the charge the moves through it can only flow through ONE of the LEDs. Since the other part of the current only flows through the other LED circuit, the potentiometer cannot have an effect on the brightness of that other LED. When all of the charge that flows through one component also flows through another, they are said to be in series with each other.

The end is nigh, since we only have two more components to go over before we make our last circuit together! First, let’s talk about…

Capacitors!

The battery is not the only component that can provide power to circuits, a capacitor can as well! You can think of a capacitor as being a very small rechargeable battery; you have to first charge one with energy in order for it to provide power to the circuit. While there are tons of

different kinds of capacitors, we will be using electrolytic capacitors. All that this means is that, just like the LED, they also have a positive and a negative lead, where the longer lead is the

positive lead and the other lead is the negative lead, again, just like LEDs! While not all capacitors are polarized, the types that we will be using are.

Last, but not least, we have…

The Transistor!“The most important invention of the 20th century!”

The transistor has three pins and it is able to act as a switch. It does this by allowing negative charge to flow from its emitter (labeled E) to its collector (labeled C) when its base (labeled B) is activated. (I know the naming conventions may be somewhat confusing, however if it does help, you can think of having positive charge flowing from its collector to its emitter instead. Which every way you think about it will work.) A transistor’s base is activated when positive charge flows into it (or when negative charge flows out of it).

“Welcome to the Resistance” Circuit:

This circuit is very unique since it doesn’t do anything on its own! The two wires sticking out of the breadboard are not connected to anything, so no charge can flow through the circuit! In other words, this circuit has an open in it. While you could just connect the wires together…why not try to hold onto the end of one of the wires with your one hand, and hold onto the end of the other wire with your other hand first? Give it a try! If you hooked everything up correctly, both of the LED’s should turn on because you just closed the circuit by allowing the charge to flow through you!

When you hold onto the wires, YOU are acting as a resistor and by doing so you are allowing charge to flow from the battery to the base of the transistor! This activates the entire circuit, allowing current to flow through the one transistor and activating the one LED. That current then flows to the base of the other transistor, activating it, allowing current to flow through it and ultimately through the other LED!

Now what happens if you let go? The one LED should turn off right away, while the other should remain on for a bit and then dim as time goes on. Why don’t both of the LEDs turn off when you open the circuit again? No current should be flowing through it because of the open, right?

Actually, for this setup, that doesn’t matter! When you close the circuit, some of the charge that passes through the first transistor not only activates the other transistor, but it also charges the capacitor! So when you open the circuit again by letting go, the capacitor discharges the energy that it was able to store. This continues to activate the transistor, allowing for energy to continue flowing from the battery to the LED. However, because the capacitor keeps loses energy during this time, it slowly loses its ability to keep charge moving through the transistor, making the LED dim.