Anders, greetings Some comments from a personal point of view - others will differ!
> 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. Yes - basic series architecture is right. Not having the PC logic ground wandering around the machine amnd using 12 (or even 24 volts) is also good to avoid noise pickup. I would not want the servo faults to E-stop the whole system and would be in two minds about the limits. On a modest size machine it is probably safe for EMC to implement the limits. In particular if the spindle stops before axis movement nasty things happen to tool and workpiece. If spindle is running the tool is likely to be safe. On a big machine you might have to have limits to protect against servo runaway (e.g. from failed encoder) which could smash up the iron. The other issues are: (a) That having separate limit switches on inputs allows you to use them as Home switches too; I always like to reference my machines even when touching-off to get work offsets set. (b) You have to be able to jog to get off the limits. Handles on a decent sized machine are generally useless and hurt when they hit you so you need a limit by-pass switch in your scheme and it would have to be monemtary contact for safety. > > 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 You might not need 3 relays if you have sufficient isolation between contacts on a single relay. Instead of 3, has your VFD got an Enable input? As with the Pico board it would be nice for the VFD to use its dynamic braking capabilities rather than having the motor coast to a halt. Also in some circumstances (e.g. DC drives) the motor/spindle KE can overvolt the drive when the supply is disconnected. The DC fuse blowing on a big stepper motor power supply can cause real problems like this. > > > > 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 See above and VFD manual > -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). Yes but you would have to put switches before the first 12v relay and risk getting noise onto PC ground. It is not IMO necessary for EMC to know which direction (+/-) has tripped - you can tell by eye - sometimes very useful to know if it is X or Y though. Hope this helps John Prentice ------------------------------------------------------------------------- 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
