“It seems to run on some form of electricity.”
Marvel’s The Avengers (2012)
One of the most confusing parts of electronic work is choosing the right wires. If they’re too thin, they may not be providing enough power. If they’re too thick, they may be taking up precious real estate if you have a densely-packed project. Figuring out the right wires to use also involves a fair amount of math. Let’s hope you were paying attention in algebra.
The Basics
Before we even get into wires, you’ll probably want to know the basics of electric power. The three common elements of power you’ll need to know are voltage, amperage, and wattage. In a (very basic) nutshell, voltage (V) is what causes the electrical current to move through the wire, amperage (I) is the rate at which it moves, and wattage (P) is your net power. Mathematically this is expressed as P = VI.
Voltage is arguably the easiest element to discern. Most electronics will list their voltage somewhere on it. If you’re working with something that plugs into a wall outlet, you’re in luck. In the United States, the vast majority of household electricity runs on 110/120V. In the U.K. and most of Europe, it’s 220/240V. Some other things that have (generally) universal voltages are alkaline batteries (1.5V) and car batteries (12V).
There are four main types of wire you can get: solid-core, stranded, braided and prefused. Solid-core wires offer the best conduction but are much stiffer and less malleable. They also offer the most natural environmental protection. Stranded wires consist of multiple strands of thin wire bundled together. The higher the individual strand count, the more flexible the wire is. Stranded wires are the most commonly recognized wires. Prefused wires are stranded wires that have been tinned and solidified during production. Prefused wires are relatively similar to solid-core wires, but are more flexible and less likely to break under strain. Finally, braided wires are the most flexible of the bunch, and also offer some electromagnetic shielding. As such, they are often used in cables that benefit from noise-reduction, such as high-quality audio cables and coaxial cables.
Most basic wiring you will buy at the store is rated at 300V for thinner wire and 600V for thicker. This means that it can handle that much voltage before becoming so hot that it may melt the insulation around it. Since voltage is relative to power and current, use those math skills to ensure you don’t overload your wires.
The current that a wire can carry is the most important aspect. Chances are you won’t be exceeding 300V in any common instance, so what you want to pay the most attention to is amperage. How many amps you are sending through your wire will determine what gauge (thickness) you want.
Gauging Your Gauge
Wire gauges work somewhat backwards. The higher the number used to denote gauge, the thinner the wire is. So, an 18-gauge wire is significantly thinner than a 6-gauge. Below is a basic guideline for amperage ratings among different wire gauges. The first amp rating is for a single-core wire, the second is for a wire that contains 3 smaller wires (usually hot, neutral, and ground):
- 18-gauge: 9.5/7 amps
- 16-gauge: 15/10 amps
- 14-gauge: 24/15 amps
- 12-gauge: 34/20 amps
- 10-gauge: 52/30 amps
- 8-gauge: 75/40 amps
- 6-gauge: 95/55 amps
- 4-gauge: 120/70 amps
- 3-gauge: 154/85 amps
- 2-gauge: 170/95 amps
While these ratings are considered the maximum, you ALWAYS want to curtail your power draw at about 80%. So, even though a 12-gauge wire can handle 20 amps in theory, it’s really only safe to push 16 amps max through it. This theory also holds true for circuits in general. Never overload your circuits!
Take a 1,200-watt microwave, for example. This microwave, plugged in to an American outlet, will pull 10 amps (1,200w/120V). In Europe it would pull only 5 amps (1,200w/240V). Using the same 14-gauge wire you could safely run one microwave in America or two in Europe.
While it is very dangerous to run more amps through a wire than it is rated for, it’s generally fine to run LESS. Most electronics have transformers built into them for this purpose. If you are building something from scratch, you may want to include a transformer of some type.
Reading Wires
The AWG (American Wire Gauge; also knows as the Brown & Sharpe Wire Gauge) is a standard measuring system for the thickness of wires. Most manufactured wires follow these guidelines. Most wires will also have a string of numbers and text printed along their entire length. Now that we know a little more about current and gauging, we can start to make sense of some of it.
The IEC cable above has 3 major elements to consider. First is 105°C, which is the max temperature the cable can withstand before melting. This can be external temperature or internal. Second is VW-1. This is a very specific rating based on the Vertical Wire flame test. Essentially it means that this cable won’t continue burning uncontrollably if it were to exceed it’s heat rating. The third is a long string of letters and numbers that reads “18AWGX3C.” 18 AWG means that the cable is standard 18-gauge. X3C means that the cable contains three smaller cables inside of it, including the ground.
There are other ways to convey a wire’s make up as well. A cable that reads 12-2, for example, means that the cable is 12-gauge and contains two smaller wires (usually no ground). 12-2G, however, indicates 12-gauge with two smaller wires PLUS a ground wire.
Color Coding
Possibly one of the most difficult tasks of reading wiring is the color coding. Different countries hold different coloring standards and if you don’t know where your wire was made, you’re going to want to make sure you’ve got it all sorted out before you send anything through it. Of course, if you are starting with a wire from scratch you can make whatever color whatever you want as long as it matches up on both sides.
The one color most of the world agrees on is green for ground. It may also be a green/yellow twist. In North America, white is almost always your neutral and black or red is usually your hot. As for the rest of the world however, your neutral is probably blue, with your hot being brown or black.
Something to keep in mind is that color coding for wires is NEVER a guarantee. You always want to double- and triple-check your wires before finalizing anything. In an age where anyone can sell anything online, bypassing OSHA and other safety standards, its always smart to know for certain what you are dealing with.
Put It All Together
Now that you have a better understanding of what wires are actually capable of, and (hopefully) the ability to read them, you should breeze right through most of your electronic projects. While is can be dangerous not knowing what to do, wire safety really only requires a bit of math skills and common sense. Presumably, you aren’t working with high voltages or fatal currents if you’re learning about this on the internet. If you are, well that’s another article for another time.