E-STOP Circuit - will this cause any problems?

[birchy]

It seems that we have different opinions of what a LIMIT switch and a SAFETY switch are. Obviously safety switches should be dual circuit and fail-safe. A limit switch/sensor is usually a single switch that tells the PLC or machine computer its current position. So I guess the safest way is to have LIMIT switches near the end of travel and SAFETY switches just before the physical stops. I think we're both on the same wavelength, but not using the same terminology!

[Ricardoco]

It seems that we have different opinions of what a LIMIT switch and a SAFETY switch are. Obviously safety switches should be dual circuit and fail-safe. A limit switch/sensor is usually a single switch that tells the PLC or machine computer its current position. So I guess the safest way is to have LIMIT switches near the end of travel and SAFETY switches just before the physical stops. I think we're both on the same wavelength, but not using the same terminology!

I may be talking tosh but this was a question that I asked when I first started thinking/designing my first machine. I got confused about home switches and limit switches and safety switches and I ended up having several physical work areas on my machine, depending on the size of the piece/part I was making, so if my machine sailed out of the physical working area I had defined, there was a good reason for it and it activated an E-stop shutting the machine down via the software stopping the program in its tracks, these physical working areas were movable/definable the in software, and a manual restart would be required whatever the condition, there were also a switches at the physical ends of all the axis, that was more brutal and just shut the power of completely. I even went and purchased a multiple input/output card (pokeys55) to achieve this. However as JAZZ has said all unexpected movement of an axis would imply a safety condition exists and should shut down the machine until it can be fully investigated..Rick