CAN-bus system wiring

Description:

Conceptually, there is not too much to the wiring of a CAN-bus network. A twisted pair runs along the network nodes, either directly or via stubs connecting to a 'back-bone' cable. Of course, in the real world, connecting lots of devices in parallel is a bit more complicated.

In our projects we have used DIN-rail bus systems, loose wiring and M12 connection systems. Loose wiring used a self defined 4-pin terminal block connection. This was used in a relatively small space, with lots of other wiring going on, so running two more wires for the CAN-bus was no problem at all.

DIN-rail connections:

DIN-rail mounted systems can have a daisy-chained connector system mounted inside the DIN-rail channel. This enables a wire-less bus- and power distribution to the nodes, thus reducing wiring clutter. We use connections that are compatible with the "T-bus" system from Phoenix Contact

Note that these connections are not suitable for hot-plugging, unless they are part of an intrinsic safe circuit. More specifically; the card-edge contacts on the printed circuit board of the modules are easily damaged by sparking of live contacts.

M12 connections

M12 'CANopen' connections:

Another wiring solution that we particularly appreciate is based on the M12 industrial connector system. This is also endorsed by CiA standard 303-1. Obviously, we use an identical pinout. Having IP68 waterproof connections when mated, these connections are particularly suited for wet or 'dirty' environments, and also for ATEX/IECEx environments.

Field bus distribution box:

Networks running at long distances and low speeds can use fairly long stub lines. This allows for a simpler wiring topology where the different nodes can be placed up to 5 meters away from the 'backbone'. Particularly on long distances, this is extra beneficial because the effective length of the CAN-bus can remain shorter, which saves on wiring cost and - more importantly - reduces voltage drops along the line.

The wiring for the backbone must be of transmission-line quality. A true 120Ω CAN-bus cable is ideal, but a heavy duty AWG22 CAT7 network cable works just as well and has much better price & availability.

Fieldbus distribution box

To aid such install, we have this field bus distribution box, which allows for up to 12 cable segments to be joined together. This is done with 5-pole spring terminal connections. The connections are mounted in an IP67/NEMA4X rated polycarbonate enclosure with 12 M16 holes for cable glands. Integrated termination resistor and 2mm multimeter probe-points allow for easy configuration and diagnostic of the network wiring.

Diagnostics:

For network diagnostics, we recommend a Peak CAN interface with BusMaster software. Our toolchain can generate the message database for all the devices in the network so that BusMaster can show meaningfull data (except for messages that are encrypted).

Availability: