Re: [EE} Protecting CAN bus

Hi David,

Yes, you're correct.

Sean


On Sat, Jun 28, 2025 at 9:31 AM David C Brown <[email protected]> wrote:

> Yes I am using the correct termination resistors and have a ground
> reference in the cable.
>
> My boards are designed for through hole components but i night be able to
> cludge SOT23s in.
> Am I right that one connects cathode1 and cathode2 to the tmo lines of the
> bus and common cathode to ground?
> __________________________________________
> David C Brown
> 43 Bings Road
> Whaley Bridge
> High Peak                           Phone: 01663 733236
> Derbyshire                eMail: [email protected]
> SK23 7ND          web: www.bings-knowle.co.uk/dcb
> <http://www.jb.man.ac.uk/~dcb>
>
>
>
> *Sent from my etch-a-sketch*
>
>
> On Sat, 28 Jun 2025 at 11:37, Sean Breheny <[email protected]> wrote:
>
> > There are specialized TVS diodes meant for use with CAN. One I've used
> > before is the PESD1CAN,215 from Nexperian. They have lower than typical
> > capacitance to avoid affecting the signal.
> >
> > I would put these TVSes on each node.
> >
> > Do you have termination resistors at each end of the cable?
> >
> > I assume that you have a "ground" reference wire in the cable as well to
> > make sure that the common mode voltage at each node isn't too large?
> >
> > I would say that any time you have wires of significant length entering
> > your house there should be lightning protection directly to a ground rod
> > right before the point of entry to the house. This should probably be gas
> > discharge tubes to be able to handle much greater current than TVSes. You
> > would think that the risk would be non-existent since the wires are
> running
> > close to the ground but that's not true. A lightning strike anywhere near
> > those wires could cause momentary potential differences of thousands of
> > volts between those lines and the local ground.
> >
> > Sean
> >
> >
> > On Fri, Jun 27, 2025 at 1:35 PM David C Brown <[email protected]>
> wrote:
> >
> > > I am using a CAN bus with MC2562 drivers for a home control system.
> > > This allows a unit in my hall to monitor and control various things in
> my
> > > garage:  car door, pedestrian door, lights, alarm.
> > > The garage is some 50 meters from the house and I use CAT5 cable
> running
> > in
> > > conduit at ground level for the bus.
> > >
> > > Naturally I am concerned about lightning and other nasties so I am
> > fitting
> > > a bidirectional TVS diode on each side of the bus.
> > > My question is:  do I need those diodes on every device connected to
> the
> > > bus or is it sufficient to fit them only on the two units at each end?
> > > I ask because I have a suspicion that putting more TVS diodes on the
> line
> > > is degrading the signal
> > >
> > >
> > > __________________________________________
> > > David C Brown
> > > 43 Bings Road
> > > Whaley Bridge
> > > High Peak                           Phone: 01663 733236
> > > Derbyshire                eMail: [email protected]
> > > SK23 7ND          web: www.bings-knowle.co.uk/dcb
> > > <http://www.jb.man.ac.uk/~dcb>
> > >
> > >
> > >
> > > *Sent from my etch-a-sketch*
> > > --
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