Re: J1939-11 physical connection on IEC terminal blocks?

On 23/12/14 08:26, Vincent Royer wrote:
> Hi all,
>
> At my shop, we have standardized using the Deutsch 3 way splitter and connector
> parts for doing all our J1939 connections on our commercial truck chassis.
>
> However, we are doing very complex systems involving several nodes in a small
> area.  To facilitate wire interfacing for the input / output and power signals,
> we have started using IEC Din-Rail terminal blocks. However, to date, we have
> not used these terminals for the J1939 connections.
>
> My technician asked if he could use 3-level signal/signal/shield IEC din rail
> terminal blocks, in which the shield terminal is connected right down to the din
> rail.  The idea is that when there are several J1939 nodes being installed in
> near proximity, we could use several of these 3-level terminal blocks, and
> simply insert jumpers to interconnect them. Then, connected to the last terminal
> would be a typical 120 ohm resistor.
>
> Here's an image of this type of connector.  We have jumpers which push in to
> interconnect any level to the terminal next to it.
>
> http://www.connectwell.com/media/2836181-CDLG2_5.gif
>
> This will allow us to bring the backbone into the panel, terminating it only
> once at the first terminal rail.  the "jumpers" would now become the backbone,
> with the nodes each only a couple mm apart.
>
> Does anyone see any potential issues with this arrangement?
>
> Thank you!

If you connect the cable shields to the earth terminal, then the DIN rail will 
also be connected to the cable shields. If the DIN rail is screwed down and 
making contact with chassis metal, then large earth current could flow through 
the cable shields if a remote CAN node also has its shield connected to chassis, 
and all the chassis components are not well connected (problems can happen after 
years of corrosion and vibration).

To avoid these problems, only one point in the system should be connected to the 
chassis.

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