On Thursday 15 October 2020 14:48:56 Alan Condit wrote: > Hello All, > > I periodically try to start Linuxcnc without turning on my CNC > controller. When I do I get the error message that indicates it is not > finding the 7i76. However, when I turn on the controller before > Linuxcnc is initialized my steppers growl until Linuxcnc is > initialized. > > So, I have been thinking about putting a power relay in the controller > that would not turn on the power to the stepper power transformer > until after Linuxcnc initialized using some signal like > “machine-is-on”. So I would turn on power to the controller box before > starting Linuxcnc but that would only turn on the 24v field power. The > 5v power to the 7i76 comes from the 5i25 board. > > The lathe spindle power is currently controlled by a relay activated > by machine-is-on, but I would probably change that to spindle-enable. > > Does this idea make any sense? > > Alan
Somewhat Alan. I am doing similar things after rebuilding the interface for enough i/o to do it with. To use the most extreme example, my g0704, all motor power is enabled by stages, controlled by the F2 machine on/off signal. This involves 2 i/o pins, controlling 2 40 amp 400 volt SSR's, wired so that all the stepper power comes on first, along with a 50 ohm 200 watt resistor to start charging the PMDC spindle motors capacitor banks. 2 seconds later that 50 ohm gets shorted by the second timer hitting that SSR, applying full power to the spindles psu. This machine draws about 3.5 amps once powered up, but without that staging, may trip a 30 amp breaker in the main service. Now its a 20 and hasn't tripped in a couple years although a spindle reverse while doing rigid tapping does hit that breaker at very close to 20 amps. Its a 90 vollt, 1hp rated motor, but abused by a psu that puts out around 127 volts, so is making about 2 hp at that instant. Since Jon's pwm-servo amp that I use 2 of for PMDC spindle motor control is a 4 quadrant controller, it recovers the motor energy when told to stop it, charging those caps up to around 170 volts by the time it has actually stopped and well above the ratings of those caps, but when it has stopped, the reversal is allowed thru and most of that surplus charge is used up re-accelerating it in the other direction. And its been doing that for around 4 years. The overvoltage on the caps is gone long before any heating from leakage has occurred. The actual turnaround time is in the 400 millisecond range, from 3k revs one way to 3k revs the other way. The armature mass is the majority of the reverseing mass, so low gear at 1500 revs is quite similar. The reversal is staged, first bringing the motor to a halt while blocking the reverse, but when stopped the blocking is disabled, and the motor is ramped back up to whatever speed is selected. I also do this reversal staging on both lathes, but there the mass of the chuck is much more important. On the sheldon, with a nearly 40 lb chuck mounted I have made a display for it, and even with a vfd's slow response, at 100 revs, it travels only .25 turns between the stop signal to the vfd, and actually getting stopped. Its actually slower on TLM with its 5" chuck but thats in deference to the fragility of the drive parts. Without the reversal staging in hal, it strips the teeth off the $7 belt and burns up the $13 plastic drive pulley. Its supply is similar, driving a 1 hp treadmill motor. Another 90 volt motor running on about 110 volts. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
