Interconnection
An introduction to circular connectors and cables
By Rolf Horn, applications engineer, Digi-Key Electronics H
ousing multiple pins or contacts for transferring electrical power, signals, or data, circular connectors are cylindrical electrical devices
of varying sizes that are designed to withstand a range of harsh environments. Also referred to as circular interconnects, their circular construction affords them additional ruggedness and resistance to vibration and impact damage, outside signals or interference, incursion from environmental contaminants, and pressure or temperature extremes.
Due to their high performance in these extreme conditions, circular connectors and cables find broad uses in industrial and factory automation applications, medical devices, security and defence systems, aerospace, and more. Circular connectors encompass a wide array of product offerings from standard circular connectors to DIN, Metric, Hermetic, Push-Pull, Keyed, Mixed Signal, and Micro or Nano versions. Hybrid options are also available that combine power, signal, and data into a single device. This article will primarily focus on standard circular connectors and cables, including their basic construction, designations and codes, selection criteria, and more.
Circular connector construction Thanks to their cylindrical shape, circular connectors have a higher strength-to- weight ratio than any other connector shape. As already mentioned, this enhanced strength gives them added resistance to impact damage, outside elements, and decoupling, while giving them durability in applications with frequent mating cycles.
The number of internal contacts as well as the layout of those contacts varies by connector and application type to ensure correct alignment and insertion into a compatible mating device. Circular
32 April 2023 Figure 2: Basic construction of a male circular connector. (Image source: CUI Devices) Figure 1: Basic construction of a female circular connector. (Image source: CUI Devices)
connector shells are often constructed with threads to allow for more secure screw- in connections where vibration or other factors would potentially cause unwanted decoupling. Other types of connection systems include bayonet locking, push/pull locking, and snap lock.
From a high level, each circular connector consists of four main areas (Figures 1 and 2): ● Contacts: The internal pins and sockets housed in the connector used to form the electrical connection. A mated pair consists
Components in Electronics
of male contacts and female sockets.
● Insulator: This component encapsulates the contacts and insulates them from each other and the connector shell. It also provides proper spacing of the contacts and holds them in the correct position. ● Shell: As the outer cover of the connector, the shell protects the contacts and insulator while providing the alignment and connection mechanism for pairing two connector halves. ● Accessories: These can include pins, keys, rings, clamps, gaskets, and additional
components utilized to guide, secure, position, and seal parts of the connector.
Common circular connector designations and codes Perhaps the most well-recognized type of circular connector is the M-style standard utilized for connecting sensors and actuators in industrial network applications. “M” simply calls out the size of the metric thread on the coupling nuts and mating receptacles, which gives us the common M5 (5 mm diameter fasteners),
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