Re: Long CAN bus

Hello Chuck,

Message received, so I guess the transition succeeded.

Nice to hear your experiences with long CAN busses. My experience with=20
this kind of CAN busses is in greenhouses. Speed 50 kb/sec and distances=20
up to 1 km (3000 feet). Here we use thicker wires 0.75 mm2 (AWG18 I=20
guess is the US standard). Sometimes also in these environments they=20
have to add repeaters and bridges to get a reliable overall system. It=20
depends a lot on the local environment.

And yes also we get units for repair (broken transceiver chip) mostly=20
caused by lightning. As this company is delivering over the whole world,=20
maybe these greenhouses are located in Florida.

BTW I think I know why Florida is the lightning capitol of the world. It=20
is caused by the war between the democrates and the republicans in this=20
state every 4 years. Prepare yourself today and maybe again also the=20
next weeks :-)

Cheers

Kees

Op 2-11-2020 om 21:39 schreef [email protected]:
> This message is partially a test to see if my unsubscribe of one email
> address and subscribe from another worked, but, I thought that I would al=
so
> contribute:
>
> In my application (outdoor ride-on railroad signal system,
> http://MiniRailSolutions.com) I use CAN bus to connect control nodes arou=
nd
> the railroad.  These busses are very long (over 1,500 feet) and low speed
> (less than 25 kbps) using MCP2551 drivers and 120 ohm terminators.
>
> As the bus length got longer I was having reliability issues.  I started
> looking at the bus with an o-scope and discovered that my issue was not
> noise or reflections but rather simply that the signal amplitude was very
> low.  After doing some bench testing with a couple 1,000 feet of CAT5 und=
er
> my bench, I discovered that when I switched to using 1k terminators the
> signal was much better.  I think I now have field bus segments up to 2,00=
0
> feet long running fine.  So, it appears that, when using very low speeds,
> amplitude is more important than reflections, etc.
>
> Since several customers require bus runs of well over 4,000 feet I have
> developed a "dual-port" version of my node which supports 2 CAN busses.
> These are used as message bridges between segments and allow splitting th=
e
> bus into shorter segments.
>
> I have also had to go to isolated CAN drivers and an isolated DC-DC suppl=
y
> to address ground potential differences and lightning protection (my test
> area, Florida, USA, seems to be the lightning capitol of the world) - hin=
t
> TVS diodes are not good enough!  I can tell you horror stories of the
> effects caused by lightning arrestors on commercial power lines (shunt
> strikes to local ground).  One railroad is located right next to a 500,00=
0
> volt substation - fun.
>
> I sure have learned a lot in dealing with it over the past 10 years - and
> have the scars to prove it.  Part of the story here:
> http://www.minirailsolutions.com/living-with-lightning/
>
> Cheers,
>
> Chuck Hackett
> UP Northern 844, Mitch-Cal Shay #2
> Owner MiniRail Solutions (http://MiniRailSolutions.com)
>
>
>
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