Circular connectors, also called “circular interconnects,” are cylindrical, multi-pin electrical connectors. These devices contain contacts that transmit both data and power. Cannon (now ITT Tech Solutions) introduced circular connectors in the 1930s for applications in military aircraft manufacturing. Today, you can find these connectors in medical devices and other environments where reliability is essential.
Types of Circular Connectors
Circular connectors typically feature a plastic or metal shell surrounding the contacts, which are embedded in insulating material to maintain their alignment. These terminals usually pair with a cable, and this construction makes them especially resistant to environmental interference and accidental decoupling.
Differentiating Circular Connectors
In addition to differentiation by the number of pins (typically three, six, or eight per terminal), we can distinguish circular connectors by their manufacturing specifications, size, attachment angles, and modes of connection and disconnection.
- Standard: A “standard” circular connector typically refers to a connector whose design conforms to either German or American military standards.
- DIN Spec (Deutsches Institut für Normung, the German national standardization authority): DIN circular connectors adhere to German electrical standards. DIN standards include high-frequency capability and hallmark features like a protective metal shell and notched, rounded terminations. This construction ensures they pair with the correct mates.
- MIL-Spec (military specifications): Manufacturers design MIL-Spec connectors according to best practices for use in military and aerospace applications. These rugged connectors are ideal for high-impact use and are highly resistant to environmental extremes. Some MIL connectors are effectively hermetic, or airtight, thanks to a strong epoxy seal around the terminal. Most MIL connectors are waterproof.
- Micro or Nano: Microminiature and nanominiature circular connectors feature smaller pin and jack diameters and more narrowly spaced contacts. This construction helps save surface space across the face of the terminal, and it reduces the connector’s added weight to the component.
Like most kinds of electrical connectors, circular connectors come with a variety of termination styles. The type of termination you choose determines the nature of the connections between electrical contacts in each of the connector’s components. Options vary regarding cost, ease of connection and disconnection, and resistance to tampering, wear, and environmental damage.
- Insulation displacement: The pins in the plug pierce or push aside insulation around the corresponding jacks in the socket, making contact and forming an electrical connection.
- Soldering: Using an intervening metal with a low melting point, the metal touches both contacts to create a permanent corridor for electrical current between the components.
- Wire wrap: Wires connected to the socket side of the connector attach to the other terminal. The wires wrap around the plug’s jacks, so an exposed segment touches the jack.
- Screws or lugs: External hardware adheres to threaded (screws) or un-threaded (lugs) holes in the protective shield around each terminal to hold the connection in place.
- Crimping: A contact barrel compresses around a conductor to complete the electrical connection.
Circular electrical connectors are available in a range of contact and shell sizes, measured in diameter, according to the specific purpose of the connection. Sensors and other delicate, high-sensitivity applications are ideal for smaller shell diameters; larger shell diameters are better suited for transmitting power.
Advantages and Disadvantages
Circular connectors are an ideal choice for applications that require an electrical connector with a more rugged terminal. Their cylindrical shape makes them especially resistant to mechanical turbulence and impact damage. However, the circle’s surface area limits the arrangement of pins and jacks on the face of a circular connector; connectors with rectangular faces can fit more contacts with adequate and even spacing onto a smaller surface area.