Welcome to Wiring 101! For those of you who have no experience in wiring, and would like to incorporate it into your builds.
I am no expert on wiring therefore I had some knowledge dropped on me by someone who knows their stuff. Jesse Haworth is my brother and is a current Biomedical Engineering major at the University of Iowa. He has assisted me in creating this article for the sake of your education. or shall I say “enlightenment”? XD
Before you get straight into wiring things up it is important to know the basics of circuits. A circuit is basically the flow of electrons (aka electricity) through a wire. A few definitions we will use are:
- Current: the flow of electrons per second. Or speed of the electric current.
- Voltage: the electric potential difference between two points in a circuit. To put more simply, the amount or size of the electric current.
- Resistance: a component’s resistance to electric flow.
There are also a few basic components in most every circuit:
- Voltage source: this basically means a battery, or power source, which creates a voltage difference in the circuit.
- Wires: these provide a path for electricity to travel.
- Resistors: this is anything that resists electricity flow, such as a light bulb that uses the resistance to make light.
- Switch: this simply allows or inhibits the flow of electricity.
Those definitions may have been confusing so here is an analogy with water flow that may help you understand.
Electricity, like water, flows down the pressure gradient. By this I mean that it will naturally flow from points of high pressure or elevation to low pressure or elevation. Water in a higher pipe will flow downhill to a lower pipe. In the same way electricity in a wire of high voltage will naturally flow to a wire of lower voltage.
In the diagram water flow can be related to current. The pressure difference in the pipes is related to voltage. Resistance is basically the same thing as in a circuit, anything that resists flow, in the water example it could be a water wheel using the flow to power a mill. The water pump acts just as a battery does, creating a potential difference in flow.
Now that we know these principles let’s take a look at a basic circuit.
Because electrons are negatively charged they will flow away from the negatively charged end of the battery and towards the positively charged end. In practice for what you will be doing the direction of flow won’t matter much. The main thing to keep note of is the positive and negative ends of the batteries and components you will be working with.
The light bulb is a resistor and by resisting flow it creates light. Because it is a resistor there is a voltage difference on both sides of it. Some lights will specify which end of the component goes with which wire and others will be able to go both ways. Check each of your components to make sure you hook them up correctly.
Uh oh, Math
One last thing to know in this basic circuit is the relationship between Voltage, Resistance, and Current. This all can be summarized into the equation: V = I x R, where V = voltage, I = current, and R = resistance. This equation is referred to as Ohm’s Law. You might find it weird that current isn’t a C but that is because C is used for something else with circuits that you don’t need to worry about quite yet.
Now for a few units:
- Voltage is measured in volts, no surprise there.
- Current is measured in amps. Fairly often you will see current measured in milliamps, abbreviated mamps, this just means 0.001 amps. So 1000 mamps are in 1 amp. We will work on conversions later.
- Resistance is measured in ohms, represented by the greek letter omega: Ω. You will also see resistance measured in kilo-ohms or k-ohms which simply means 1000 ohms. Therefore, 1 k-ohm equals 1000 ohms.
Here I will show you how to use the V = I x R equation.
For the sake of the example let us say that we do not know how much current is flowing through the wire. We can find this out by doing some simple math.
- If we rearrange Ohm’s Law we get the equation V / R = I.
- Since we know the voltage across the resistor, 4 v, and the resistance value, 2 ohms, we can solve for I: 4 v / 2 ohms = 2 amps.
Pretty simple right? Let’s do it again but say we only know current and resistance but not voltage.
- In this case we can use the basic Ohm’s Law: V = I x R.
- From here we simply plug in current and resistance to find: 2 amps x 2 ohms = 4 volts.
Using Ohm’s Law if you know any two of the value in the equation you can use it to find the other one. This will come in handy very throughout your experience with circuits.
A Series Circuit
Unfortunately all circuits are not as simple as the one we previously looked at, so there are a couple more things you should learn before we get to wiring up a circuit.
The first circuit we will look at is a series circuit.
A series circuit is a circuit where each component is in line with one another, just like most Christmas tree lights. Each component connects to a wire that it shares with the next component in line.
The main characteristic of this type of circuit is that current stays the same. Current is the flow of electrons, because the amount of electrons going through the wire isn’t changing current stays the same as it goes through each component. This works the same way with water, as water flows through a pipe past several turbines the amount of water that is flowing doesn’t change but it might lose pressure as it goes past each turbine or whatever is resisting movement.
In a later lesson we can break down the math in calculating the values at each component. But for now all you need to know is:
- Current is the same all around the series circuit.
- Total resistance of the circuit equals the sum of all the resistances.
- RT = R1 + R2 + R3
- Total voltage of the circuit, or the battery, equals the sum of the voltage at each component.
- VT = V1 + V2 + V3
A Parallel Circuit
The second type of circuit you must know about is a parallel circuit.
To help define what a parallel circuit I must introduce another work to you, a node.
- A node is any part of a circuit only connected by wires and not separated by components.
- For example 8, 7, 6, and 5 are one node because there are no components separating them.
- Voltage is the same across an entire node.
In a parallel circuit all the negative ends of the components are connected to the same node and all of the positive ends of the components are connected to the same node. Because of this in a series circuit voltage is the same across all the components. Unlike in a series circuit current is the same.
If we bring this back to the water analogy imagine the splits in the wires going to different nodes like a split in a water pipe. The amount of water flowing would split similar to how the current does, but the voltage or the water height would stay the same.
Once again there is more math involved that we can delve into in a later lesson but for now all you need to know is:
- Voltage is the same across all component in a parallel circuit.
- Total current equals the sum of the currents going through each component.
- IT = I1 + I2 + I3
I hope this lesson was helpful and opens up the world of wiring! This way you can light up your builds with some real power! Weather you want to put some lights on some cool sci-fi costumes. Or put some on a set piece so you can have a computer panel. Be creative and have fun!