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.
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