On Sunday 13 December 2015 16:39:16 andy pugh wrote: > On 13 December 2015 at 11:01, Gene Heskett <[email protected]> wrote: > >> Feed the cap bank through a resistor. > >> Use a (cheap $5) solid state relay to bypass that resistor when > >> LinuxCNC is turned on. > > > > I had largely discounted that idea because the first cycle surge is > > likely high enough to fuse a 40 amp Crydom. It trips a 20 amp > > service breaker instantly when its master switch is closed. That > > would also be complicated by needing a high side drive for it. > > The relay won't see the surge, because what the relay does is bypass > the surge absorbing resistor. > > The relay would go on the AC input side, so you would only need one. > > You don't need a "high side driver", you need a 5V signal from > LinuxCNC.
I got that grokked finally Andy, so I just ordered 4 of them, 40 a, 480 volt from MPJones, a tad over a $50 bill by USPS. Now to find a pair of uncommitted BoB pins. I'll keep one for a spare, but the third one will replace the ice cube I am controlling the vacuum cleaner with. I'll use one to switch the line, one to bypass the resistor in a few seconds, and one to switch the vacuum. 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) Some mill pix are at: Genes Web page <http://geneslinuxbox.net:6309/gene/GO704-pix> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
