Circular Connector Types, Pins, & Options

Circular connectors, also called “circular interconnects,” are cylindrical, multi-pin electrical connectors. These devices contain contacts that transmit both data and power.

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 Connector Types

In addition to differentiating by the number of pins (typically three, six, or eight per terminal), circular connectors can be distinguished based on manufacturing specifications, size, attachment angles, and connection/disconnection modes.

Standard: A "standard" circular connector refers to designs that conform to either German or American military specifications.

DIN Spec (Deutsches Institut für Normung): DIN circular connectors meet German electrical standards. They often feature a protective metal shell and rounded, notched terminations, providing high-frequency capability and ensuring proper mate alignment.

MIL-Spec (military specifications): MIL-Spec connectors are designed to meet military and aerospace standards. These robust connectors are ideal for harsh environments and high-impact use, offering high resistance to environmental extremes. Many MIL-Spec connectors are hermetic, with a strong epoxy seal around the terminal for added durability. Most are also waterproof.

Micro or Nano: Microminiature and nanominiature circular connectors have smaller pin and jack diameters, with closely spaced contacts. This design allows for reduced surface area on the terminal and decreased weight, making them suitable for compact and lightweight applications.

Circular Connector Terminal Options & Types

Circular connectors come with a variety of termination styles, each affecting the nature of the connection between electrical contacts. The choice of termination type influences factors such as 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 the insulation around the corresponding jacks in the socket, making direct contact to form an electrical connection.

- Soldering: A low-melting-point metal is used to join the two contacts, creating a permanent electrical path between the components.

- Wire Wrap: Wires connected to the socket side of the connector wrap around the jacks on the plug, creating an electrical connection via the exposed wire segments.

- Screws or Lugs: External hardware, such as screws (threaded) or lugs (unthreaded), secures the connection by attaching to holes in the protective shield around each terminal.

- Crimping: A contact barrel compresses around a conductor, completing the electrical connection by securing the conductor in place.

Circular electrical connectors are available in a range of contact and shell sizes, with diameters chosen based on the specific application. Smaller diameters are suited for sensitive applications like sensors, while larger diameters are better for power transmission.

Advantages and Disadvantages of Circular Connectors

Circular pin connectors are well-suited for applications that demand a rugged and durable terminal. Their cylindrical design provides enhanced resistance to mechanical turbulence and impact damage. However, the round shape of the connector limits the arrangement of pins and jacks, reducing the number of contacts that can fit onto the connector’s surface. In contrast, connectors with rectangular faces can accommodate more contacts with better spacing on a smaller surface area.