Lester Caine wrote: > Jeshua Lacock wrote: > >> I am guessing there is not an easy way to detect this condition, but I >> wanted to see if anyone else has any thoughts on the subject. >> > > I would have thought that if the motor turned more than 1/2 a turn or so but > the > encoder feed produced no pulses then this would be an easily detected error > condition? Nope, if NO motion was commanded, as at power up, this would look normal. Now, when you give a command to move, and no motion is detected, that WOULD cause a following error. > If you are getting pulses from one channel only, then that is very > easily detected ... > Surely a 'runaway' like this SHOULD be handled by the servo driver? > The old G320 does not handle this. Supposedly the G320X does. > Is there a market for a module to monitor the two encoder feeds and us it in > conjunction with either the index pulse or an extra source that indicates > that > the encoder should be giving output? Probably the best way is to monitor motor voltage. If you have significant voltage at the motor terminals, but no motion detected by the encoder, then something HAS to be wrong. This might not be a real hard circuit to build, especially if a crude sensing is all you need. Maybe the motor terminals could be connected to a resistor divider, RC filter and a dual-polarity opto-coupler. Set the dividers so motion below 10% speed does not light the LEDs in the opto. Have a circuit that detects pulses on BOTH encoder signals. If you get the LEDs lighting up, but even one encoder channel shows no transitions for a millisecond or more, trip the E-stop. The RC filter is needed to remove the full-voltage PWM pulses that the G320 drive produces, and only sense the average voltage.
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