Jon Elson wrote: > I include an all-electronic version of this in all my controller boards, > and users can add external safety controls as they deem necessary. > A latching relay is basically what you are looking for, it would then > need a separate reset button. The problem with making it mechanical > through the red button is that someone intentionally or accidentally > jamming the button could prevent the E-stop action from happening.
Same here ... The breakout board has both estop and reset, AND requires charge pump from the computer, AND uses 5V from the computer which can be used to provide an opening action estop in addition to the closing one. If computer power is lost then you have to 'reset' the enable signal before any output can be activated. In my own case I simply have power switches for the mains outputs, with over rated solid state relays to provide computer control. These should probably go through an additional contactor as well as the electronic interlocking ;) I am told so should the power to the stepper drivers, but if they are designed to switch OFF when the control signals are killed, then trying to rapidly kill power on the stepper motor PSU should not be necessary? I don't see the logic on stepper motor drivers that REQUIRE a signal to disable them? From a safety point of view you should need to ENABLE them to make them work? But the debate here seems to be is it better to lock the movement, or unlock it, and that depends on the mechanical arrangements that the motors are driving? Not that one should be relying on any actuator to hold something safely! Nothing should move under it's own weight when power is killed? But equally it may be necessary to USE the motors to move something out of the way after an emergency. Many of us work alone, so safety circuits ALSO have to be practical - not that anybody works without safety guards nowadays :) Having had a couple of close saves with the spindle starting up when it should have been locked out. I keep the separate power controls! You need to be able to move the machine - perhaps with a dial gauge in the spindle - so a single interlock is not enough. -- Lester Caine - G8HFL ----------------------------- Contact - http://lsces.co.uk/wiki/?page=contact L.S.Caine Electronic Services - http://lsces.co.uk EnquirySolve - http://enquirysolve.com/ Model Engineers Digital Workshop - http://medw.co.uk// Firebird - http://www.firebirdsql.org/index.php ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
