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CANOpen Fun with M12 Connectors

Since I have been working on communicating with my Festo CPV10 valve manifold, I have learned a lot about M12 connectors and cordsets.

The Festo CPV-10-GE-CO-8 CANOpen valve terminal has a DS303-standard 5-pin M12 plug (male) connector. The second generation Festo valve terminal (CPV-10-GE-CO2-8) allows the choice of
DB9, M12, and terminal block. In my CANOpen research so far, the most common connectors are DB9, RJ45, M12 (for harsh environments), and terminal block (especially for I/O).

My preference is dual RJ45 connectors for normal environments, and dual M12 connectors for harsh environments. M12 connectors are typically IP67 rated, are available with 3, 4, 5, and 8 pins, can be shielded or unshielded, are quick to connect (unlike most DB9’s), and are vibration resistant. M12 connectors are used most often to connect sensors back to a controller, often via a concentrator or fieldbus box. Other uses include CANOpen (of course), DeviceNet, Profibus, and Banner light curtains.

Since nothing stays simple, there are a number of M12 variations. The ERNI catalog lists five polarizations: A,B,C,D, and P. The A or normal polarization is the most common, and is used by most sensors and CANOpen; the B (or reverse; used for Profibus) and D (used for Ethernet) polarizations are available, but not as common.

I looked at M12 connectors and cordsets from Phoenix, Binder USA, Lumberg, ifm efector, ERNI, Turck, Hirschmann and Tyco/AMP. It’s interesting to see what is available that could be used with CANOpen

Connector availability is good, with plenty of choices for PCB mount, free-hanging, and bulkhead mount in male, female, and right angle versions. Single-ended cordsets with a male straight, male right angle, female straight, or female right angle connector are common.

However, I only found Male/Female double ended cordsets; I have not found any Male/Male or  Female/Female cord sets. All the Tees I found had 1 male and 2 female connectors. I think this comes from M12 connectors use in sensors. Extension cables have to be M/F. A 1M/2F Tee splits one female connector into two female connectors, allowing two sensors to be wired to one connector (most sensor boxes use female connectors, and some do support two inputs to one connector).

This can work well for CANOpen systems, too. DS303 does not provide guidance on how to connect the whole system, but DS102 does for DB9 connectors. Applying the Interconnected Bus Line approach from DS102 works perfectly for M12 connectors: start off with a M12 female terminator, connected to M/F cable. The cables are connected together using a Tee (with 1 male, 2 female connectors) for devices with 1 male M12 connector (with one of the Tee’s female connectors connected directly to the device’s M12 male
connector or via a M/F stub line cord set), and connected directly to the device for devices with Male & Female M12 connectors. The bus ends with a M12 male terminator.

The parts required are available, except perhaps for the female terminator (but that can be made easily). However, compared to RJ45 cables, the cost is high. Using Allied Electronics pricing (8/17/08) for Phoenix, a male terminator (1507816) is $17.96, a CANOpen Tee (1507793) is $44.91, a Sensor/Actuator Tee (1683468) is $24.06, a CANOpen M/F 0.3m shielded cable (1518258) is $47.72, and a 0.3m M/F Sensor/Actuator cable (1519040) is $21.70, and a shielded 0.3m Sensor/Actuator cable (1500884) is $31.49. Long cables don’t cost
a lot more; for example, a 3m Sensor/Actuator M/F shielded cable (1500910) is $40.04. I’m not sure what the difference is between Phoenix’s recommended CANOpen cable and the “Sensor/Actuator” shielded cable, or between the “CANOpen” Tee and the “Sensor/Actuator” Tee.



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