Hi all, could I have some comments on the following E-stop circuit idea. The core idea emerging from thinking about this is to wire dangerous things in series(wire OR) and use the end result of this in parallel(wire AND). That way the E-stop chain is cut if device1 OR device2 OR device 3... fails, and the resulting signal stops EMC AND cuts power to VFD AND cuts power to servo drives AND ...
Here is what I have come up with: start at the HAL pin E-stop-out. It will be high whenever EMC thinks it's OK to go out of E-stop. E-stop-out drives the coil of a NO(normally open) relay. This relay connects +12 V to the beginning of the E-stop chain only if E-stop-out is high. On the +12V wire, a number of NC(normally closed) switches follow: Red E-stop buttons (2), Limit switches(6), NC relays on the servo amps(3). At the end of the chain we are going to have either +12V if everything is OK, or 0V if we are in E-stop. Use the +12V to power the coils of three NO relays (coils in parallel): 1. one relay connects +5V to E-stop-in telling EMC everything is OK 2. one relay grounds the Poweron/ input of a Pico Systems power switch - that will give power to the servo drives. 3. one relay connects 230 VAC power to a VFD which powers the spindle motor If the E-stop chain breaks for any reason all of the relays will go to their NO state making E-stop-in go low, cutting power to servo drives, and cutting power to the VFD. If this sounds confusing there's a picture at http://www.anderswallin.net/temp/e-stop.png which might help... (the E-stop chain is the blue line, the VFD relay would obviously be two-pole, a transistor driving relay1 is needed) Some questions I have: -wiring three relays in parallel at the end of the chain will result in three times the current needed to pull one coil of the relays. Is this going to be a problem ? (other than that the +12V supply must cope) -is it a good idea to just cut the AC power to the VFD in an E-stop situation ? are there any other better ways to safely stop the spindle ? -should I also hardwire the servo drive amp-enable signals so that they go low on E-stop? -If I connect the common terminal of the limit switches to the 'upstream' end of the E-stop chain, can I wire the unused NO output of the limit switch to another HAL pin ? This way an E-stop due to a limit switch could be diagnosed by EMC as coming from a specific limit (+/-) and axis (XYZ). thanks for any comments, Anders ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
