DeviceNet Media Cable with 4-wires

Hi guys,
Our office acquired a module and AB E3 overload to test in the office but we couldn't get a hold of DeviceNet media cable. Looking at the module and the overload, it looks like it essentially just has 4 terminals where I can connect 4 different wires, maybe of size 16/18 AWG. Would this work okay? I have no experience in DeviceNet and couldn't really find documentation on wiring media other than the Rockwell provided cable.

We use Teldor cables for devicenet, they are cheaper than AB:
http://www.teldor.com/catalogue.php?actions=list&parent_cat=829

Ideally you'll have signal wires with 120 ohm characteristic impedance, and it helps to have blue/white be a twisted pair.

But for a test hookup, use anything you have around. Do be sure to put on the two (and only two !) 120 ohm terminating resistors.

Hi Ken, How do you mean two? If I go out of my module on CANH (White) and CANL(Blue) to the E3's CANH & CANL, I will be installing one 120 ohm resistor on the E3 between CANH and CANL. Where does the second one go? Does it go on the module side between CANH and CANL?

When you hook up just a PLC device and a single slave device, you're essentially creating a trunk line with zero-length droplines, so you put one terminating resistor on each side.

Because the network is so short and droplines can really be up to 6 meters in length, it's just as good to put both the terminating resistors in the same spot.

I used to say that the DeviceNet Media Design and Installation Guide was like Moby Dick; it's an important piece of literature but it's so boring that it just sits on the bookshelf and nobody actually reads it.

Thanks Ken, I couldn't find any 150 resistors lying around so I gave it a shot and it worked. The comms line between the module and the device is very short.

Glad you got it working ! I've commissioned hundreds of E3 overloads and like them very much.

A couple of points, because we see these questions so often:

1. DeviceNet, like all CAN-based networks, uses 120 ohm terminating resistors. RIO and DH+ used 150 ohm terminators so there's sometimes some confusion.

2. 90% of DeviceNet problems come from improper installation. Don't assume that because a short bench network functions without terminating resistors that a larger network will as well, or that proper wire isn't necessary.

Ken Roach said:

2. 90% of DeviceNet problems come from improper installation.....

Click to expand...

I'll raise you on that Ken, I'd go to 99% easy....