I think E-Stop feedback is important for diagnostics.
I have been running home runs to all the E-Stops to a terminal block next to the master control relay. The MCRs I have been using have 1 channel that is 24 VDC so I can run a wire from the "return" of each E-Stop to a PLC input. I found some nice 3-screw terminal blocks that make this real clean.
I work in the harsh, wet environment of the food industry. I started this format after finding an corroded E-Stop that the only contact that still worked was the one for the PLC input. This way I am monitoring the working contacts and not stacking more contact blocks.
The downside of this is that you have to do a bit of code to deduce which switch opened as you will lose all of the downstream E-Stops on the chain. In the rare instance that multiple E-Stops are pressed, it will create "moving target" at the HMI. Never heard a complaint on that (yet). The other downside is that the electrical prints look real messy if you don't plan ahead and use consecutive inputs.
I always bring the control current in as an input. I have also been stacking a PLC input on the reset push button. With these you can request a "reset" if the E-Stop chain is made but no control current and point to a welded contact on the "monitor" circuit or an open channel B if the reset fails.
I also use the home runs for the E-Stops on non-HMI systems... there is nothing worse than opening E-Stop box after E-Stop box looking for the wet one. Just work from right to left on the terminal block until you find voltage, then go open the right box first rather last as it usually goes in my trial and error experience.
I have been running home runs to all the E-Stops to a terminal block next to the master control relay. The MCRs I have been using have 1 channel that is 24 VDC so I can run a wire from the "return" of each E-Stop to a PLC input. I found some nice 3-screw terminal blocks that make this real clean.
I work in the harsh, wet environment of the food industry. I started this format after finding an corroded E-Stop that the only contact that still worked was the one for the PLC input. This way I am monitoring the working contacts and not stacking more contact blocks.
The downside of this is that you have to do a bit of code to deduce which switch opened as you will lose all of the downstream E-Stops on the chain. In the rare instance that multiple E-Stops are pressed, it will create "moving target" at the HMI. Never heard a complaint on that (yet). The other downside is that the electrical prints look real messy if you don't plan ahead and use consecutive inputs.
I always bring the control current in as an input. I have also been stacking a PLC input on the reset push button. With these you can request a "reset" if the E-Stop chain is made but no control current and point to a welded contact on the "monitor" circuit or an open channel B if the reset fails.
I also use the home runs for the E-Stops on non-HMI systems... there is nothing worse than opening E-Stop box after E-Stop box looking for the wet one. Just work from right to left on the terminal block until you find voltage, then go open the right box first rather last as it usually goes in my trial and error experience.