On Saturday 19 December 2015 19:46:23 Gene Heskett wrote: > On Saturday 19 December 2015 18:34:23 Gene Heskett wrote: > > On Saturday 19 December 2015 18:07:58 Gene Heskett wrote: > > > My google-fu seems unusable for this. > > > > > > The SSR's arrived this afternoon, and I need to figure out what > > > sort of an R to use as buildout as I think I will enable it with > > > the same 0-12 volt signal that enables the pwm servo amplifier I > > > am using to drive the spindle. > > > > > > They are rated 3-32 volts in, and <10 ma to fire. But I've no real > > > data on the opto from sparkfun that I am using to drive the pwm > > > servo's 12 volt enable. I've no clue how many mills it can > > > actually source. > > > > > > I will go see how many it can spare with a 1k load resistor > > > though. > > > > That turns out to be around 10.4 mills, but my testing found another > > problem with that idea, so apparently I must use a 2nd one, and find > > a pin to drive it, such that the power input is switched by the > > presence or lack thereof, of a charge pump signal at 500 hz from > > LCNC. Why? powered up, but LCNC is not running, the default outputs > > of the 5i25 are a logic one. So that enables the servo amp (and this > > SSR) even if it has no controlling signal, which in turn defeats the > > soft-start. And I've no clue 5 months later, if I have a spare pin > > on the first BoB. I do not believe I do without ripping out my > > ability to drive an A/B/C 4th axis. > > > > Fun & games, including finding a mounting place for both of them. > > That I found, on the outside of the box unforch. Might be advisable > to make a cover just to keep the NEC happy. At some point an > indeterminant time in the future. Its up on a high shelf I have to > climb a small ladder or tall stepstool to access it. > > No pins left on P3 of the 5i25 though as I had set it up originally > for an A axis, but because of driver space in the box, will have to be > considered as a package in a separate driver box if and when I need it > but it will be up to PCW to tell me how to load 4 stepgens when one of > them is going to be driving P2. So pins 8-9 are now free to be used > for these 2 functions as I have now commented out any references to > the A axis in both the .ini and .hal files. But again, because the > LCNC off is a logic high, I will build the charge pump detectors to > drive the - terminal of the SSR. With enough filter to prevent the > powerup-powerdown 1 or 3 cycle triggers associated with turning it on > or off from the power switch. [...] Charge pump continued;
I found a pdf, on a different brand of SSR that carries the same SSR-40DA designation. >From that on=>2.4 volts, off = <1.0 volt, but on the next line it says the trigger current 7.5 mills/12 volts. So I am somewhat confused. The BoB can only swing 5 volts, and its current delivery into the usual voltage doubler, 2 diode, 2 capacitor circuit would be limited by what it can deliver as pullup. At 500 hz, the pump capacitor should be perhaps 10% that of the output capacitor, which for power up surges should be directly across the input to the SSR. But my choices there are limited by my lack of a decent assortment of tantalum caps. Electrolitics are out because of the low voltages involved since they will deform and lose capacitance in just a couple years. Now, I know the T=RC enters into this, and that T is a millisecond up and a millisecond down. So that would seem, since R is in owms and C is in farads, that its going to take some multi-microfarad caps to make this work at the leasurely charge pump frequency available when there is no "base thread". I've found some assortments, one even coming with a carry box with 18 drawers and 5 of each value starting with 1 u-f, and am considering buying such a kit. See figure 7 at <https://en.wikipedia.org/wiki/Voltage_doubler> but with the diodes reversed in order to drive the - terminal of the SSR. + terminal will be grounded, and the left hand current source connected there also. By that means I hope to prevent the mains switch power on/off's from falsly triggering it. I am using a similar circuit, with smaller electrolitic caps that I know will fail eventually, driving a scrap bin to-220 transistor which drives a 24 volt P&B to switch the vacuum cleaner. This power on surge as the 5 volts come up on the BoB is strong enough that it gets about a .2 second power on when the mains is turned on. Causes a noisy growl as it winds back down. Poor choice of caps coupled with excessive gain in the to-220. Has anyone else concocted such a circuit, and were you able to get enough pump power out of it running the BoB on 5 volts, with the pump at 500 hz, to run an SSR without resorting to an external current booster? 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
