On 5/23/2012 10:45 PM, Jon Elson wrote: > Kent A. Reed wrote: >> Of course all roads lead to LinuxCNC, but is there some reason one >> couldn't/wouldn't start with one of the many microcontroller chips or >> even ARM-based SoCs and build a separate watchdog for the purpose of >> detecting and stopping servo runaway in its tracks? It would seem to me >> almost any has more than enough capability to do so. >> > Measuring the output of the drive seems like an important measurement. > It might be > hard to get this from a G320 drive, or a number of others as the > voltages are > high and the average reading would be much better than seeing all the PWM > pulses. I think a very simple circuit, largely analog plus some one > shots and > a logic gate could do it. Probably 3 chips per axis. Some RC feeding an > opto-coupler, a 74HC123 and a gate package. If the output to the motor > exceeds some value (maybe 5 V) for some short time, and there are no > pulses on BOTH encoder signals, that is a fault, and it trips the E-stop. > Parts cost should be about $3 per axis, in single quantities. > > Jon > > -
Well, shoot, can't we make it more complicated? This sounds like a Don Lancaster solution straight out of the pages of Popular Electronics :-) In the good old days I could think this way but 40 years of digital electronics have fried my brain. All kidding aside---thanks for an elegant solution, Jon. Regards, Kent ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
