Am 13.12.2010 22:52, schrieb Kirk Wallace: > On Mon, 2010-12-13 at 16:36 +0100, dambacher-retrofit.de wrote: >> Am 13.12.2010 15:56, schrieb Stephen Wille Padnos: >>> I don't think this is a concern. People who have hardware that removes >>> the need for a base thread very likely also have a watchdog feature in >>> their hardware. I know the Mesa and Pico products do, and I believe the >>> Pluto does as well. (I'm not sure about Motenc and STG) >> Motenc has a watchdog circuit barking at 8 or 16ms (selectable) if you don't >> write DACs or the wd register. >> >>> - Steve > > Just thinking out loud. > > I see the PWM controller has this in the doc's: > " > Jumper JP4 can be selected to enable or disable the watchdog timer on > the board. When enabled, the watchdog will force the board into > Emergency Stop mode when the rate generator registers have not been > written to in 20 mS. > " > > I guess one issue is that the integrator will need to make sure that the > PWM controller e-stop signal out is connected to all of the e-stop > slaves and not just EMC2, because if the controller initiates a watchdog > fault, we can't rely on EMC2 to handle it. A proper e-stop system would > commonly be set up this way, so it shouldn't be a problem. Also, this > watchdog only validates EMC2.
All commecial systems I saw were wired this way. if the control fails, the estop circuit gets triggered, main relay goes off, no power on drives. New VFDs have the possibility of doing a controlled emergency stop. They need power to do this. so you neeed addititonal logic to shut down power correctly, e.g. timed after estop. > > The Pluto doc's are a little more interesting: > " > Before configuration and after properly exiting emc2, all Pluto-P pins > are tristated with weak pull-ups (20kΩ min, 50kΩ max). If the watchdog > timer is enabled (the default), these pins are also tristated after an > interruption of communication between emc2 and the board. The watchdog > timer takes approximately 6.5ms to activate. However, software bugs in > the pluto_servo firmware or emc2 can leave the Pluto-P pins in an > undefined state. > " > An independent wathcdog might be prudent. > > With the Motec one can pet the dog internally with dac-write (from EMC2) > or from an external source (using watchdog-reset as an input rather than > output)? Only internal source (dac-write or direct write to wd-register) can reset the software watchdog. The Motenc handbook sais about function: "The watchdog output is Active low. If the PC software enables the watchdog circuit and fails to reset the watchdog timer within the configured amount of time, the watchdog circuit resets the entire board and sets the watchdog output to logic 0. All DAC outputs, Digital outputs and Encoder counter are reset to zero. The watchdog output pin can be used to monitor this state by an external controller if needed. This pin is available on Header J8 pin 1. Software can also read the state of this pin at register location 6 bit 22. " So besides triggering the watchdog it triggers internal reset and sets all pins/DACs to zero. If you wire correctly, your machine stops immediately. bye ulf -- --------------------------------------- Ulf Dambacher i...@dambacher-retrofit.de --------------------------------------- ------------------------------------------------------------------------------ Lotusphere 2011 Register now for Lotusphere 2011 and learn how to connect the dots, take your collaborative environment to the next level, and enter the era of Social Business. http://p.sf.net/sfu/lotusphere-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
