Working with Wire
When someone mentions the word wire, they are more than likely referring to a flexible, cylindrical piece of metal that can vary in size from just a few millimeters in diameter to several centimeters. Wire can refer to either a mechanical or electrical application. An example of a mechanical wire could be a Guy-wire, but this this guide will focus on electrical wiring.
Inside a stranded wire
Electrical wire is a backbone of our society. There is wire in houses to turn on lights, heat the stove, and even talk on the phone. Wire is used to allow current to flow from one place to another. Most wires have insulation surrounding the metallic core. An electrical insulator is a material whose internal electric charges do not flow freely and, therefore, does not conduct an electric current. A perfect insulator does not exist. However, some materials such as glass, paper, and Teflon, which have high resistivity, are very good electrical insulators. Insulation exists because touching a bare wire could allow current to flow through a person's body (bad) or into another wire unintentionally.
Here are some topics you might want to explore before reading about wire:
How to Solder: Through-Hole Soldering
Voltage, Current, Resistance, and Ohm's Law
Stranded vs Solid Core Wire
Wire can come in one of two forms: solid or stranded core.
Solid wire is composed of a single piece of metal wire, also known as a strand. One very common type of solid wire is known as wire wrap.
Various colors of solid core wire
Stranded wire is composed of many pieces of solid wire all bundled into one group. It is much more flexible than solid wire of equal size.
Various colors and sizes of stranded wire
Applications of Solid and Stranded Core Wire
Since stranded wire is more flexible than solid core wire of equal size, it can be used when the wire needs to move around frequently, in a robot arm for example. Conversely, solid wire is used when little or no movement is needed, such as prototyping circuits on a breadboard or protoboard. Using solid core wire makes it easy to push the wire into a breadboard and plated through holes of a printed circuit board.
|Solid Core Wire Used in a Breadboard with the Battery Babysitter||Solid Core Wire Soldered into a Plated Through Hole with the Button Pad Breakout Board|
Trying to use stranded wire on a breadboard or plated through hole can be very difficult depending on the thickness as the strands want to separate as they are pressed in.
The image on the left shows the wire strands being twisted by giving them about 180 degrees of twist along the length of the strip. The image on the right shows the wires being tinned with soldered. Apply excess solder to allow the flux to work, and pull the extra solder off with the iron yielding a solid cylinder of wire.
The term ‘gauge’ is used to define the diameter of the wire. The gauge of a wire is used to determine the amount of current a wire can safely handle. Wire gauge can refer to both electrical and mechanical. This tutorial will only cover electrical. There are two main systems for measuring gauge, American Wire Gauge (AWG) and Standard Wire Gauge (SWG). The differences between the two are not critical to this guide.
An approximate scale of several different gauges of wire
The amount of current that a wire can carry depends on a few different factors, for example the composition of the wire, wire length, and condition of the wire. In general, thicker wire can carry more current.
An approximate wire thickness to current capability chart
Here at SparkFun, we typically use 22 AWG wire for prototyping and breadboarding. When using a breadboard or PCB, solid core is perfect because it fits nicely into the holes. For other prototyping/building involving soldering, the stranded core is #1, just be sure not to let too much current run through a single wire. It will get hot and could melt!
SparkFun carries a variety of both solid and stranded 22 AWG wire.
However, there is still an option to use 30 AWG wire wrap if you need to go smaller.
|Wire Wrap connecting to a PCB's small SMD pins that are broken out on the Hardware Mouse Jiggler.||Wire Wrap used in projects with small spaces of the Heartbeat Straight Jacket.||"Green" Wire Repairs with a bad PCB design or damaged pad.|
How to Strip a Wire
Safe, durable electrical connections begin with clean, accurate wire stripping. Removing the outer layer of plastic without nicking the wires underneath is critical. If a wire does get nicked, the connection may break or an electrical short may occur.
No nicks or gouges. These wires have been properly stripped
Manual Wire Stripper
A simple manual wire stripper is a pair of opposing blades much like scissors. There are several notches of varying size. This allows the user to match the notch size to the wire size, which is very important for not damaging the wires. Depending on the manufacturer, there may be additional features that include a locking mechanism, have an ergonomic handle, and the ability to cut screws.
Although a knife would also strip the wires, it may also damage the wire by nicking the metal or cutting into it. Using a knife to strip wire is also really dangerous! The knife can easily slip and cause wicked injuries.
Self-Adjusting Wire Stripper
There are also self-adjusting wire strippers that automatically strip the wire by placing a wire in the middle of the teeth and squeezing the handle. These take almost any wire and perfectly strip the wires every time. Depending on the manufacturer, there may be additional features included to cut or crimp insulated/non-insulated wires.
Wire Wrap Tool
If you are using a wire wrap tool to wrap a wire around a pin, there may already a built-in stripper blade in the middle to strip the thin wire. Simply place the wire between the blades and pull.
Stripping the Wire with Manual Wire Strippers
By simply squeezing the handles of a manual wire stripper about ¼" from the end of the wire or the desired length, using the correct notch on the tool, and then twisting it slightly, the insulation will be cut free.
Then by pulling the wire strippers towards the end of the wire, the insulation should slide right off of the wire.
Tips, Tricks, and Hints
It is important to match the size of wire to the correct notch in the stripper. If the notch is too large, the wire will not get stripped. If the notch is too small, there is a risk of damaging the wire. Using an undersized notch means the strippers will close too far, digging into the wire underneath. With stranded wire, the tool will cut off the outer ring of wires, decreasing the total diameter of wire and reduce the strength of the wire. A nick in solid core wire will severely reduce the strength and flexibility of the wire. The likelihood of the wire breaking upon being bent increases significantly.
This wire was not stripped properly, there are gouges and missing strands
If a wire does accidentally get a nick in it, the best plan of action is to cut the damaged part of the wire off and try again.
How to Splice Wires
Prepare the wire by stripping the wires ends using a wire stripper. If you are working with stranded wire, try twisting the ends to group the strands together and tinning the tips before soldering.
Cut a piece of heat shrink to cover the exposed wires. Slide the heat shrink through one of the wires. Make sure to slide the heat shrink away from area where you are splicing.
Face the wire terminals toward each other and touch the exposed ends together.
Hold the wires together by using tape to hold the wires in place against a soldering mat.
Add solder to the wires. Try not to leave the soldering iron on the wires too long. The insulation can melt away exposing more wire.
Ensure that the underside of the wire is also soldered.
Flip the wire over and spread solder over the wires. If necessary, add flux and solder to cover wires.
If you are using heat shrink, slide it over the terminal to insulate the connection. Apply heat to the heat shrink from a soldering iron or a hot air rework station.
|Heat from a Soldering Iron||Heat from Hot Air Rework Station|
When complete, the heat shrink should fit over the exposed wire.
You can also try hooking and twisting the wires together in a Western Union splice (a.k.a. Lineman's Splice). This method is ideal for solid core wire but it can be used on stranded wires.
How to Crimp an Electrical Connector
An electrical connector is a device for joining electrical circuits together using a mechanical assembly. The connection may be temporary or serve as a permanent electrical joint between two wires.
There are hundreds of types of electrical connectors. Connectors may join two lengths of wire together or connect a wire to an electrical terminal.
The word crimping in this context means to join two pieces of metal together by deforming one or both of them to hold the other. The deformity is called the crimp.
The metal has been deformed to pinch the wire and hold it in place
In order to crimp connectors onto a wire, a special tool is require for the crimp pin. There are several different styles of crimpers available depending on the crimp pin.
Ratchet Crimp Tool
The best crimper has a built in ratchet. As the handles are squeezed together, it will ratchet and prevent the jaws from opening back up. When enough pressure has been applied, the ratchet will disengage and release the crimped part. This ensures enough pressure has been applied. This style of crimper also has a wide jaw to cover more surface area on the connector.
Ratchet Crimp Tool for Spade Connectors
Manual Crimp Tool
Manual crimping tools can achieve nearly the same results, although it requires the user be much more vigilant. This style of crimper is generally less sturdy. Attention must be given while crimping to ensure the jaws are lined up properly on the connector. Misalignment will cause a less than desirable crimp connection. Over time, wear and tear from normal usage can also cause the jaws to become separated and not close fully. Generally, squeezing it as hard as possible will be sufficient.
Manual Crimper on the Self-Adjusting Wire Stripper for Spade Connectors
Why is this level of perfection required? A poor crimp leaves air pockets between the wire and connector. Air pockets allow moisture to collect, moisture causes corrosion, corrosion causes resistance, resistance causes heat, and may ultimately lead to breakage.
Crimping a Quick Disconnect Connector
There are several arguments for and against using solid core wire with crimp connections. Many believe crimping to solid core wire creates a weak point in the wire, which can lead to breakage. There is also a greater chance for a crimp connection to come loose with solid core wire because the wire will not conform to the terminal as well. If you must use solid core wire, it is a good idea to solder the wire in place after you crimp it.
First, the correct size wire must be chosen for the terminal size, or vice versa. Next, strip the wire. The amount of exposed wire should be equal to the length of the metal barrel on the connector, usually around ¼” or so. If the stripped wire fits up into the metal portion of the barrel with little or no free space, the connector is the right size.
A good length of wire to barrel ratio
The wire should then be inserted until the insulation on the wire touches the end of the barrel.
Good: The wire is sticking past the barrel just a little
The wire and terminal are then inserted into the crimper. The color of the terminal’s insulation needs to be matched with the same color on the crimping tool. So if the terminal’s insulation is red, use the spot marked by the red dot on the crimpers. Alternatively, if the crimper does not have color markings, use the gauge markings on the side.
The terminal should be sitting horizontal with the barrel side up. The tool is then held perpendicular to the terminal and placed over the barrel, nearest to the ring (or other connection type). To finish the crimp, the tool is squeezed with a considerable force. In general, it is almost impossible to ‘over crimp’ a connection.
After the crimp is completed, the wire and connector should still hold together after trying to pull them apart with great force. If the connection can be pulled apart, the crimp was not done correctly. It is better to have the crimp fail now, versus after it has been installed in its application. Below is a military spec chart for crimped connections.
Wrong size connector for the wire or wrong size wire for the connector.
Bad crimp. Connector was too small for the gauge of wire chosen.
Be cautious not to strip too much insulation off.
Too much insulation has been stripped off, too much bare wire exposed
It is also worth mentioning that, while not necessarily harmful, The wire should not be protruding too far past the barrel. If this happens, trimming the wire is recommended.
The excess bare wire should be trimmed off
How to Use a Wire Wrap Tool
Strip the 30 AWG wire by inserting it between the wire wrap tool’s blades. Pull the wire to remove the insulation.
Make sure to strip away enough wire to wrap around a terminal for a sufficient connection. About a 1" should be enough.
Insert the exposed wire into the hole along the side. Make sure to insert the wire on the side with the notch and place the wire in the cut along the side of the cylinder.
Insert the wire into header pin (a.k.a. post). In this case, male header pins were used on a mini-breadboard.
Rotate the tool clockwise to begin wrapping the wire around the square header pin. Hold the wire and header pins down with your other hand. Continue rotating the tool so that all of the stripped wire wraps around the pin.
Remove the tool from the pin. When completed, the wire’s insulation should start at the bottom of the pin. For a more permanent and secure connection, add some solder between the wire and pin.
If you require more connections on the same pin, wrap more wires around the top of the first connection and repeat the steps outlined above. The amount you can stack depends on the length of the header pin. Try using the wire wrap tool to wrap wires around headers on a microcontroller, LED, or resistor for prototyping.
Removing Wrapped Wires
If you need to disconnect the wire from the pin, simply use the other end of the tool and rotate it in a counterclockwise direction.
Once the wire wrap is loosened, pull the wire away from the pin.
Twisting Wires into a Braid
It is a good idea to braid long wires that are used in a project. There are a few benefits of twisting the wires together:
- keeps the project organized
- prevents wires from being pulled from moving parts
- strengthens the connection
Below is an example of braiding four hook-up wires together for a non-addressable LED. To braid your wires, twist a pair of wires in a counterclockwise pattern between your index finger and thumb using both hands. In this case, the green and red wires were twisted first.
Twist the other pair of wires in a counterclockwise pattern.
Twist the pairs of wires in a clockwise pattern.
Once finished, the wires in your project will be manageable and easier to handle. Below are a few examples with braided wires used in projects.
|Some Twisted Wires Used in the Interactive 3D Printed LED Diamond Prop Tutorial||Twisted Wires Used in the Wireless Audio Bluetooth Adapter w/ BC127 Tutorial|
Sleeves and Cable Carriers
Sleeves and cable carriers are also useful in further protecting the connection from moveable parts. The image below shows loose wires on the Shapeoko.
Below are images of wires within a sleeve and cable carrier for protection.
Labeling Complex Wiring
Sometimes it is useful to label wires using sticky notes, tape, or markers to help keep track of connections using the same color of wire, complex wiring, and to troubleshoot projects.
Labeled wires from the micro:arcade kit
Resources and Going Further
You should now be familiar with electrical wire and how useful it is in the world of electronics. Whether you’re prototyping, reworking, or building a final product, electrical wire can be your best friend. Here are some other tutorials you can explore that involve electrical wire.
- Wire is the most basic element when creating your own circuits.
- Unsure which connectors to use? Have a look at Connector Basics to get what you need!
- Want to start prototyping? Check out Breadboards to get going!
- Looking for more flexibility in your connections? Try using conductive thread in your wearables projects!
What is a Circuit?
How to Use a Breadboard
Or check out this blog post: