Auto/Manual Selector switch... one input or two?

[PeterW]

Slightly off-topic, but a couple of years ago I was working on some assembly presses for Delphi that were headed to Poland. The controls specification called out that in order for the machine to be in auto or manual, a selector switch had to positioned correctly AND that auto or manual had to be selected on the HMI. Both physical and HMI selections had to agree for the modes to be valid. And if they didn't agree the machine had to fault like as if something terrible happened.

Thats like chicken and egg, which do you select first, whichever gets you into an alarm condition.

 

[jstolaruk]

Thats like chicken and egg, which do you select first, whichever gets you into an alarm condition.

Yeah and slightly over the top. In this case the customer wanted the selector switch made first then confirmed with a HMI selection.