M12 Connector Technology

December 03, 2024

For sensor and actuator applications, the M12 circular connector with A coding is the first choice. Whether transmitting signals, data or power, the M12 connector has become an indispensable interface as an interface for device networking.

The M12 circular connector has become the universal standard for industrial plug connections. Many manufacturers offer this compact, standardized interface, which makes it attractive for industrial applications ranging from signal and data transmission to power transmission. The robust, mechanical and environmentally resistant M12 connector is named after the nominal diameter of the locking thread of 12 mm. The wide range of applications of the M12 connector is reflected in the number of mechanical codings (unique mechanical contours of the housing for specific applications) that comply with the standards of the corresponding application areas (DIN EN 61076-2-xxx).

The A-coded mechanical shape is the origin of all M12 codings; all other mechanical locking systems have evolved from it, which is why there are different codings (A, D, L, X, S, etc.), each with a different number of available contacts. Although the M12 interface can have from 2 to 17 contacts, in practice, 3, 4, 5, 8 or 12 pins are most commonly used. The number of pins depends on the various requirements. For example, sensor and power applications require 3 and 4 pins, while Profinet and Ethernet applications require 4 and 8 pins, and fieldbus, CAN bus and DeviceNet usually require 4 and 5 pins. 12 pins are required for complex signal transmission. Table 1 gives an overview of the protocols and the number of connector pins required at the physical level.

Table 1: Overview of the physical layer of the M12-A coding. Würth Elektronik offers Circular Connectors with M12-A coding with 4, 5 or 8 pins.

Precision connection system

M12-A stands for signal with DC power supply option and is particularly suitable for fieldbus applications in industrial automation. The WR-CIRCM12 series with screw lock housing and Cable Assembly is available with 4, 5 or 8 pins. Application areas include industrial environments, especially automation and robotics, as well as the fields of renewable energy, communication technology and mechanical engineering. In addition, the panel and field wireable versions of the M12 connectors are cULus certified (UL2238). All M12 connectors offer a minimum protection of IP67 or IP68 against the ingress of dust, dirt and water.

Wide range of applications

This is by no means the end of the range of applications for the rugged M12-A circular connector. For example, the IO-Link communication system can be used to neatly connect smart sensors and actuators to automation systems in accordance with IEC 61131-9 – using a 5-pin A-coded M12 circular connector connected to a three- or five-core 20-meter cable. Connections on a three-wire cable are called "Type A", and connections to a five-wire cable are called "Type B". Device connections can be fixed cables or 4- or 5-pin M12 A-coded, depending on the cross-compatibility required.

The M12-A can also handle USB connections. With USB version 2.0, it can be used as both a power supply and a high-speed data bus. The M12-A circular connector is suitable for the manufacture of rugged USB cable assemblies. In cable assemblies for USB 2.0, two power connections for V-bus and GND must be considered, as well as a twisted pair with a differential impedance of 90 ohms for the USB signals. If the connection is a mini or micro-USB plug, the ID pin can be connected like this to a five-pin M12 A-coded circular plug. The connector is shielded with the cable's shield braid. The length of the USB cable is usually between 1 m and 3 m.

The M12 connection technology is well suited as an intermediate link for industrial bus systems, in particular CANbus, RS-485, Profibus and the physical layers RS-422, RS-423 and RS-232. Although CANbus was originally designed for use with miniature D-SUB connectors, the five-pin M12-A-coded circular connector is a common interface for CANbus. Only the CAN_H and CAN_L signal pairs connected to pins 4 and 5 are necessary. In this configuration, the device can be powered. A twisted pair with a nominal impedance of 120 ohms is used for electrical transmission.

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Ms. Merinda

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