Bus Cabling

The 1-wire cabling of our modules is simply done via ethernet Cat5e cable.

This choice ensures a simpler/standard wiring and also an extremely effective cost per meter of the cable itself. The connector is an RJ45 with type B scheme as shown in the following figure

The cables are used as follows: White/Orange — common signal for OneWire communications Orange — 1-Wire signal White/Green — Not used Blue — Not used White/Blue — Not used Green — 1-Wire power source (5 Vdc) White/Brown — Field device power common signal Brown — Field device power positive signal (16 Vdc)

The right way to connect the modules is using a daisy chain scheme. Avoid stars because the cable and the modules are adapted to 100 Ohm impedance and using a star topology will change the impedance causing reflections of the signals thus risking to disrupt the communications. It is possible to realize a working star topology network but it is more art than science: the lines will not be adapted so propagation of the signal on the cable could change by simply adding or removing components or connections.

It is also possible to use stubs but they must be kept as short as possible (not more than 3-4 meters or 9-12 ft).

Have a look on this document to get a better idea on how to cable your bus: Guidelines for 1-wire reliable networks