On Monday 11 March 2019 22:11:51 Peter C. Wallace wrote: > On Mon, 11 Mar 2019, Gene Heskett wrote: > > Date: Mon, 11 Mar 2019 21:55:59 -0400 > > From: Gene Heskett <ghesk...@shentel.net> > > Reply-To: "Enhanced Machine Controller (EMC)" > > <emc-users@lists.sourceforge.net> > > To: emc-users@lists.sourceforge.net > > Subject: [Emc-users] until I get chips for C1G, moving everything to > > the 7i76 > > > > For PCW. > > > > I have 100's of 1N914's. And I'm going use some 12 volt coil 4pdt > > relays in din rail sockets, that when on will draw around 180 ma > > from a 12 volt supply. Thats well within the on ratings of a 7i76 > > output. Are the 1N914's enough to protect the 7i76 from the off edge > > back emf, or do I need to src some heavier current ratings than the > > 200 mills they are rated at? I'm bearing in mind the speed of these > > 1N914's compared to the many times slower common 1N4000 power > > diodes. Speed is likely the important item, but whats Peter got to > > say? > > > > I am also thinking of using one of those same relays to start and > > stop the spindle coolant pump by driving it with spinena, since the > > pump is heating the water 20F or more if left on overnight. Anybody > > see anything wrong with that? > > > > Thanks a bunch. > > > > 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) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > The 7I76s driver chips have built in flyback protection (basically a > zener diode that keeps the output MOSFET on if the source --> drain > voltage exceeds about 40V) This dissipates the stored inductive energy > in the output MOSFET. At higher currents its possible to exceed the > energy absorption capabilities of the MOSFETS so its neccesary to use > a flyback diode (with a flyback diode the bulk of the stored energy is > dissipated in the relay coil) Either a 1N914 or a 1N400x diode are > fine (speed is not important)
Good, and many thanks Peter. 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) 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
