[Halld-controls] Ethernet switch reliability and PLC control

[David Lawrence]

Hi Elliott,

     Correct me if I'm wrong, but I didn't think the reliability of the 
hardware itself was the only issue with the switch. The fact that it 
serves a lot of other traffic for unrealted systems and may require 
occasional configuration changes that have nothing to do with the PLC 
are both potential issues. Do we have any way of gauging those risks?

Regards,
-David

On 6/3/11 3:15 PM, Elliott Wolin wrote:
> Hi,
>
> At the Controls meeting yesterday we discussed the reliability of PLC
> control using Ethernet as the chassis interconnect mechanism, as
> compared to ControlNet, which uses a custom cable and protocol.
>
> Today I talked with Bryan and Brent about network switch reliability.
> They said the equipment they are buying these days is extremely
> reliable, as reliable as the PLC itself.  About the only switch failures
> they ever see are due to loss of power.  They say that as long as all
> the switches in the PLC control path are on UPS power we should not have
> any problems.
>
> Thus I conclude we do not need to consider using ControlNet as an
> alternative to Ethernet/IP for the PLC chassis interconnects.  Note that
> we own two or three (expensive) ControlNet modules that we may be able
> to sell to Hall C, who uses ControlNet mainly because the Ethernet
> option was not available when their system was designed.
>
> Comments...?
>
> Thanks,
>
>