Re:'It Was the First Time I Cried in the Operating Room'
by jacquesm on Saturday January 27, 2018 @03:39AM
(#16245391)
That's the perfect solution, and actually quite close to what I ended up doing. But you are still going to have to (1) detect the fact that there is an e-stop in progress, (2) restore the machinery to stable state afterwards and (3) lift the e-stop condition at some point.
And all of those will have a software component.
I've written a bit more about how it worked in another comment.
The big thing to keep in mind here is that an ST is a very limited machine when it comes to IO and that just about every port was already occupied so I somehow had to make this work safely without having additional ports for e-stop i/o in the budget.
If I had to do it again in the present I would never have consented to using such an I/O hamstrung platform to begin with and I would use an FPGA to do all the control logic.
I'd be very interested in hearing more about this! I've recently re-designed the safety system for my company's product, and I chose to keep it purely hardware based (using safety relays) rather than involving any software, purely because it's so much harder to guarantee that software will be failsafe.