On Wednesday 06 January 2016 02:36:57 Bertho Stultiens wrote: > On 01/06/2016 03:05 AM, Gene Heskett wrote: > [snip] > > > The idea being that when that drain goes low, it will charge the > > .22, thru the diode, essentially maintaining that charge state. But > > when LCNC is stopped, that drain will go high (to 25 volts) as the > > supply is turned off, and as it goes high, so will the far end of > > that .22, carrying the + terminal on the third SSR far enough to > > trigger it. > > [snip] > > That means you want to use the SSR to act as a bleeder, which is > activated when the main power is shut off. > > This is a good idea, but the use of SSR is a problem. An SSR has a > TRIAC or an SCR as switching element, which cannot be turned off. The > device is in the on-state once a current flows until the current > reaches under a holding threshold. This feature is no problem in AC > systems, but is generally bad in DC systems. > > When you turn off the machine and the SSR starts to bleed, and then > turn on the machine before the caps are completely empty, then you > will have the bleeder load on there permanently.
Exactly the reason for the forced time delay in the turn on as I described. That, and the low voltage AC in series with the load resistors to encourage its turn off when the DC volts gets down to the 6 volt range if it does not recover from lack of sufficient holding current, but that may be several T=RC's depending on the minimum holding current of the individual device. This applies to the spindle psu only, and other initializations of the machine, like homing & touch offs, can continue while this is taking place. These toroids have a quite low level hum, difficult to hear over the other background noise, as there is a 20" box fan with a 20" HEPA filter on the back of it, trying to keep the air clean enough that I can air brush finish without having to knock off the dust nibs after its setup, so I may duplicate the at-speed led and tie it to the output of the soft start resistor bypass control signal, thereby giving be a visual indicator that the spindle is ready to rock & roll. All that "wiring" is of course in the .hal file(s). I'll prowl fleabay though and see if I can source a power resistor in the 300 ohm range, which should shorten the T=RC time a bit if it takes too long with this small batch of 10 watt'ers that are equ to 833.33 Ohms. Spares I had bought for something else since long forgotten. Might as well use them for something. :) 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
