What’s an electrical connector？

Definition of Electrical Connectors

Connectors are parts or devices used for electrically connecting or disconnecting circuits etc. They can connect and disconnect by hands or with simple tools without requiring special tools or processes such as soldering.

Although there are various types of connectors, the large majority are one-piece types that are used alone or two-piece types consisting of a plug and socket. One-piece types directly connect printed circuit boards and wires to connectors.
Two-piece types are divided into plug and socket, the part where the plug and the socket are fitted is called the contact part, and the part where the printed circuit board or the electric wire is attached is called the connection part.

Types & Classifications

Connector Basics

There are roughly four types of connection for connectors.

1. Board to Wire

2. Board to Board

3. Input / Output

4. Others - Jumper Plugs, IC Socket, etc.

Structure and Principle

Basic Connector Structure

There are various kinds of connectors. Connectors have various structures and parts to be used, however, basically they consists of contacts and a housing.

Contact: Contact for making electrical connection with each other when connectors are connected
Housing: Main body part into which the contact is inatalled (Usually made of insulator)

Other parts will be added depending on the type and use of the connectors. The following is an example of D sub connector.

Shell: Outer case which houses the insulator and the contact
Eyelet: Fastener that fixes the housing and the shell

Connector image (Plug side)

Connector image (Socket side)

Click here for the connector product lineup

Contributors:

Connector Terminology

Before we get started discussing some commonly used connectors, let's explore the terminology used to describe connectors.

Gender

Gender - The gender of a connector refers to whether it plugs in or is plugged into and is typically male or female, respectively (kids, ask your parents for a more thorough explanation). Unfortunately, there are cases where a connector may be referred to as "male" when it would appear to be female; in the examples section, we'll point a few of those out as we discuss individual component types and explain why that's the case.

Male (left) and female 2.0mm PH series JST connectors. In this case, gender is determined by the individual conductor.

Polarity

Polarity - Most connectors can only be connected in one orientation. This trait is called polarity, and connectors which have some means to prevent them being connected wrong are said to be polarized, or sometimes keyed.

A polarized North American wall plug. By having two different widths for the plug blades, the plug will only go into the outlet one way.

Contact

Contact - Contacts are the business portion of the connector. They are the metal parts which touch each other, forming an electrical connection. This is also where problems occur: the contacts can become soiled or oxidized, or the springiness required to hold the contacts together may fade with time.

The contacts on this connector are clearly visible.

Pitch

Pitch - Many connectors consist of an array of contacts in a repeated pattern. The pitch of the connector is the distance from the center of one contact to the center of the next. This is important, because there are many families of contacts which look very similar but may differ in pitch, making it difficult to know that you are purchasing the right mating connector.

The pitch of the pins on the headers on a standard Arduino is .1".

Mating Cycles

Mating cycles - Connectors have a finite life, and connecting and disconnecting them is what wears them out. Datasheets usually present that information in terms of mating cycles, and it varies widely from one technology to another. A USB connector may have a lifetime in the thousands or tens of thousands of cycles, while a board-to-board connector designed for use inside of consumer electronics may be limited to tens of cycles. It's important that you select a connector with a suitable life for the application.

Mount

Mount - This one has the potential for being confusing. The term "mount" can refer to several things: how the connector is mounted in use (panel mount, free-hanging, board mount), what the angle of the connector is relative to its attachment (straight or right-angle), or how it is mechanically attached (solder tab, surface mount, through hole). We'll discuss this more in the examples section for each individual connector.

A comparison of three different methods of mounting the same barrel connector: (left to right) board mount, inline cable mount, and panel mount.

Strain Relief

Strain relief - When a connector mounts to a board or cable, the electrical connections tend to be somewhat fragile. It is typical to provide some kind of strain relief to transfer any forces acting on that connector to a more mechanically sound object than the fragile electrical connections. Again, there will be some good examples of this later on.

This 1/8" headphone jack comes with a strain relief "boot" slid over the cable to prevent forces on the cable from being transmitted directly to the electrical joints.

Other Connectors

RJ-type Modular Connectors

Registered jack connectors are standard for telecommunications equipment into a local exchange. The names one normally hears associated with them (RJ45, RJ12, etc) are not necessarily correct, as the RJ designator is a based on a combination of the number of positions, the number of conductors actually present, and the wiring pattern. For example, while the ends of a standard ethernet cable are usually referred to as "RJ45", RJ45 actually implies not only an 8 position, 8 conductor modular jack, it also implies that it is wired for ethernet.

These modular connectors can be very useful, since they combine ready availability, multiple conductors, moderate flexibility, low cost, and moderate current carrying capacity. While not originally intended to deliver a great deal of power, these cables can be used to deliver data and a couple of hundred milliamps from one device to another. Care should be taken to ensure that jacks provided for applications like this are not connected to conventional ethernet ports, as damage will result.

A standard 8p8c (8-position, 8-conductor) "RJ45" modular jack . Be aware that if you intend to use this type of jack to pass DC signals and power, you must avoid using connectors with built-in signal transformers

D-sub Type Connectors

Named for the shape of their shell, D-subminiature connectors are a classic standard in the computing world. There are four very common varieties of this connector: DA-15, DB-25, DE-15, and DE-9. The pin number indicates the number of connections provided, and the letter combination indicates the size of the shell. Thus, DE-15 and DE-9 have the same shell size, but a different number of connections.

DB-25 and DE-9 are the most useful to the hardware hacker; many desktop computers still include at least one DE-9 serial port, and often one DB-25 parallel port. Cables terminated with DE-9 and DB-25 connectors are widely available, too. As with the modular connector above, these can be used to provide power and point-to-point communications between two devices. Again, since the common usage of these cables does not include power transmission, it is very important that any repurposing of the cables be done cautiously, as a non-standard device plugged into a standard port can easily cause damage.