On Saturday 26 December 2020 10:08:47 andy pugh wrote: > On Sat, 26 Dec 2020 at 10:00, andrew beck <[email protected]> wrote: > > also what do people do for E stop circuits with analog systems? I > > have only used a step direction system before this > > On my lathe the main servo power supply comes via a contactor with a > 24V coil, and that coil power passes through two e-stop switches. > > LinuxCNC controls the 24V contactor coil, but the e-stop switches in > series in that circuit can over-ride. > I couldn't remember if the contactor was controlled via an ssr, or > whether it's directly from a 7i84 output. So I found this photo: > https://photos.app.goo.gl/7VSURFqEFVq9s3bk8 which suggests an SSR for > the main relay.
Same here, I have a pile of the hoymc(sp?) 40 amp 600 volt SSR's in such circuits already. In fact since my field power is 12 volts, that enough to fire 2 of them in series, so one 7i76D output controls both sides of the 250volt to the new vfd on the 6040. I can see the reflection of the lit leds thru a small hole in the box cover. Adding a contact from a relay in series with that signal would be easily done. But I'm not done yet. The mister draws enough air it keeps a bigger 125 psi 2hp compressor moderately busy, and HOT, so since it does not need that much air pressure, I've bought one of those car tire compressors but with a 120 volt motor, so it will grow a relay to turn it on with the misters pump circuit. With timers running it, it outputs about 1/4 drop of liquid 5 to 20 times a second, not enough to flood the work but does keep the tool wet. But its a lot noisier than I expected and not muffle-able as it has no identifiable intake port, so I'll have to put it in a noise containing box yet to be made. Suspended on bike tire innertube straps I think. As is from the bigger compressor, it keeps a 1/8" tool wet with kool-mist and clean enough I have cut out the motor mounts for the BS-1 from 1/2" alu with one tool, at 14k revs for a total cut length of nearly a meter, leaving a beautiful finish. Feed depth increments cannot be seen in the finished cut, moving half a mm deep a pass at 250mm feeds. This will, at virtually no head pressure, supply enough air to sweep away some of the alu mud the existing setup doesn't. And so far has used less than half an 8 oz coke bottle of kool-mist mix. > There is a wire back from the 24V coil terminals to a 7i84 input. That > is used to inform LinuxCNC if the e-stops are activated, triggering > the software e-stop and turning the machine off. > I seem to recall making sure that there was a protection diode, so > that the voltage as the coil turned off didn't damage the 7i84 input I forgot to put one in on one of my relay circuits and I have a 7i76D port that may stick on, but hasn't since I installed the diode. Dumb old man... > pin. > > So, e-stop drops out the contactor, the drives turn off, LinuxCNC > spots that the coil is de-energised and e-stops itself to match. I think we are on about the same page, just need to find the round tuit. Thanks Andy. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
