> -----Original Message----- > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com] > Sent: April-08-18 9:52 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] ESTOP and Drive Enable handling. (SAFE OFF) > > On Wed, 4 Apr 2018 12:57:03 -0700 > "John Dammeyer" <jo...@autoartisans.com> wrote: > > > In the past ESTOP appeared to be pretty simple a 12V or 24V control signal > was routed through any number of Normally Closed (NC) switches and then > run into relays and or opto-isolated inputs. Any ESTOP even would then > interrupt the control voltage and relays would open dropping all power. > > > > However things have changed a bit. With PCs in the mix, rules changed > and PCs and control systems could stay active but anything in hardware > dangerous to humans was now switched off by the signal interruption. > > > > Enter a wide variety of motor controllers. The HP_UHU has an active low > ESTOP IN/OUT signal. A low on the ESTOP input shuts off power to the > drive control logic. If the drive has a fault, it brings this line low too and any > other HP_UHU drives are also then pulled into ESTOP mode. I think this > would be better identified as ENABLE rather than ESTOP. > > > > The STMBL AC Servo drive I'm currently working with has an ENABLE high > input. So when Low it's disabled and stepping pulses can't move the motor. > > Then working with frequency inverters I come upon the term "safe torque > off" and are pretty sure there are special requirements on this signal. I think > this particularly apply to DC motors since failure mode close may cause it to > run at full speed.
I believe that the ESTOP signal should remove power to relays that supply energy to anything that could hurt a human. That means, motor voltage, heater voltage, lasers and pneumatics. Once the ESTOP is released that same set of relays must require a separate action to re-enable them. SO that someone doesn't just release the ESTOP and a motor starts up cutting through the rest of a man's arm for example. Keeping the ENABLE as a switch that must be cycled off and then on allows the software to also disengage all motion. Then, if safety warrants it, the drives can be re-enabled and JOG feature used to pull back our out or away from the human pinned by it. Way back when I worked in The Netherlands there were pretty strict rules about what ESTOP did and how equipment behaved after ESTOP was released. I don't know what the regulations are now. And ideally the separate ESTOP circuit must be Normally closed so a broken wire has the same effect. John ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
