On Saturday 09 May 2020 07:50:29 Dan Henderson wrote: > Good morning Gents— and I use that term loosely ;)
According to one 55-ish checkout lady at the grocery store I resemble that remark. Easily impressed I think. Now, putting on my CET hat: First off, a 2n7000 is an N channel mosfet. Rated at 200 milliamps it could a bit puny switching a 5 volt relay coil in a relay big enough to do the job, the 60 volts is fine, but I think I'd feel better seeing half an amp for a current rating, and thats probably not going to come in a to-92 package, It s/b ok if the relays run from 12 or even 24 volts. Your protection diode should be installed such that it turns on if the drain voltage goes above the supply voltage, or anode to the coil-drain, and cathode to the + supply rail. Diode current flow is always considered to be electrons into the point of the arrow. That means your bob pin output voltage is backwards. It should be nearly zero in the m5 (off) state. And near 5 volts in the m4 (reverse on) state. Use exactly the same circuit to control the braking relay with the motor armature connected to the moving contacts so that the braking R is placed across the motor armature when its enabled, and the output of the reverse relay is connected to the motors armature when its off. hal can fix that logic polarity problem at the parport in your hal file. see man hal_parport for syntax. But it could then be wrong when linuxcnc isn't running. But it should be ok when the pwm drive is off anyway. And if no response, you may have already blown that transistor with a wrongly polarized diode, replace both and try it again. Also, if useing linuxcnc to drive the bob, linuxcnc must be in the motion-enabled state before any of this works. HTH, stay well Dan. > I’m trying to test out the basic premise of a reversing circuit. I’ve > got a breadboard on the table here and I’m attempting to send a CCW > signal from the BOB to a mosfet gating chip (2n7000) middle leg. It’s > used to switch on the relay coil which in turn activates the DPDT > switch of the relay. It no workie. The relay coil requires 12 Vdc. I > have a diode between pins a and b of the coil otherwise it would > immediately actuate the contacter. In theory this setup should work. I > measured output voltage of the CCW pin @ 4.8 vdc high and when on an > M3 it drops to .387 vdc. Essentially the mosfet holds the ground > captive until the middle leg receives a signal (CCW) then it allows > the ground to “source” and the relay should go “click”. > > Not sure if any of this makes sense, it barely makes sense to me but > the circuit was designed by an expert so I’m not going to question > that, maybe my implementation. > > On Sat, May 9, 2020 at 1:15 AM John Dammeyer <jo...@autoartisans.com> wrote: > > One of the greats in computer science has a series of interesting > > quotes. https://www.azquotes.com/author/15849-Niklaus_Wirth > > > > One I really like is: > > "The belief that complex systems require armies of designers and > > programmers is wrong. A system that is not understood in its > > entirety, or at least to a significant degree of detail by a single > > individual, should probably not be built." ~ Niklaus Wirth That statement by Wirth always made me think Seymore Cray had to be quintuplets. :-) > > I often wonder if LinuxCNC has reached this point. > > > > Although so far, Andy Pugh appears to be that single individual so I > > may well be wrong. > > > > John Dammeyer > > > > > -----Original Message----- > > > From: Gene Heskett [mailto:ghesk...@shentel.net] > > > Sent: May-08-20 9:44 PM > > > To: emc-users@lists.sourceforge.net > > > Subject: Re: [Emc-users] Fluctuating RPM using CUI ATM 10 encoder > > > > > > On Friday 08 May 2020 22:36:35 Dan Henderson wrote: > > > > Thanks for the examples. I'm not going to lie, I've got some > > > > homework to do on this. You guy's make this sound easy but to > > > > the new guy looking in? No so much, lol > > > > > > Don't be glum Dan, you've already demo'd to me that you WILL get > > > there. > > > > > > The fact that LinuxCNC is being further developed, literally as I > > > type this, even if the basic premise is decades old, can't be > > > emphasized enough. One of the reasons I posted snips of my old > > > code, old but still after the new words were added to the hal > > > recipe, was to demo that, far more than any finger pointing at > > > Jon's example. If it works, its right. > > > > > > I apologize to Jon if it was taken that way. > > > > > > I cannot today even run that code, because the hardware under it > > > has changed. For the better is an arguable point because that > > > driver Jon makes is a no compromise device doing exactly what you > > > tell it to do with zero drama. It can now make that same motor > > > break all sorts of stuff between it and the chuck it spins if I > > > hadn't taken measures to tame the violent acceleration that drive > > > is capable of making it do. OTOH, that 1 hp rated motor can now > > > deliver nearly 2hp because the psu I built out of junk box parts > > > makes 35 more volts and 10x the current that cleared the fuse in > > > the OEM configuration. But it also gets the job done. Its had > > > stuff in that 5" chuck that weigh half what that whole lathe > > > weighs, and made the part. > > > > > > [...] > > > > > > > > Yes, I'm pretty sure it still does. But, yes, this is OLD > > > > > STYLE hal code, for sure. > > > > > You can combine any newsig / linkps / linksp into one net > > > > > command, with > > > > > > > > > > net signal-name pin pin pin ... > > > > > > > > > > And, you don't have to tell it the signal type, it gets it > > > > > from the first pin. > > > > > > > > > > Jon > > > > > > 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 > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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
