A more simple design for a "soft start" is just to place a "thermistor" in series with the transformer (either side). This device will offer a high resistance at first, then heat up and the resistance lowers to about an Ohm. It is completely passive and very low cost. They are used in many consumer devices from TV sets to computers and in larger industrial devices too. The guys below will help you to select a part then offer free samples. You can even use them in parallel if you need to absorb more power.
The higher resistance is only needed for a second or so. You select the part based on current and the thermal "mass" of the part For really large power designed the thermistor can control some other device. I think it is better then using a timer because the thermistor actually looks at the inrush current and reacts to it by changing its resistance,then use the voltage drop across it to control something else. For info here http://www.ametherm.com/inrush-current/inrush-current-faq.html On Wed, Feb 3, 2016 at 11:46 PM, Gene Heskett <ghesk...@wdtv.com> wrote: > On Wednesday 03 February 2016 21:38:27 Jon Elson wrote: > > > On 02/03/2016 02:09 PM, Gene Heskett wrote: > > > Now I have spent 20 minutes doing a slow dance on those 2 > > > buttons, and haven't tripped the breaker yet, probably > > > more than 50 full cycles. > > > > Well, still don't exactly know why it wasn't working > > before. Did these charge pumps DIRECTLY drive the SSRs? I > > can easily see how marginal or decaying analog outputs from > > a charge pump could do unwanted things to an SSR, like make > > it conduct ONLY on one polarity for a couple cycles as the > > charge pump cap was draining. In fact, if you give typical > > SSRs marginal input voltages, I'll bet most of them will do > > this. > > > > Jon > > > You could have hit it squarely there, Jon. Perhaps the mosfet/hexfet > output might have been replaced with a comparator with a bit of a > schmidt trigger hysteresis so that the output wasn't ever in that grey > area. I'd be a bit spooked about running it all on a normal logic > voltage supply though. I did note that I had quoted the wrong voltage > yesterday, coming out of the buck switcher, its display says 25.6 volts, > not 12. But since the original 4000 family of cmos logic can and has > survived on 28 volts on my watch with only nominal heating while being > switched at 1/4 microseconds speed, I'm sure it could survive a nearly > dc mode. RCA only rated it for 15 volts in their propaganda. > > There is such a circuit I've seen someplace that used 1 gate of a 4050 > inverting buffer, with it driving the other 5 gates in the package so > the end result is non-inverting, and that can easily supply 50 mills of > output, and ack the SSR data we need 4 mills. > > One could adjust the trip point, since it would be at nominally 50% of > VCC, simply by adjusting the supply VCC, so if the bucker was turned > down to about 7.5 volts, the on/off response would essentially duplicate > the nominally 3.75 volts on point of the hexfet. > > Hind sight, 20-05, I never thought of that when I laid it out in pcb. :( > Perhaps I should? That would make the board wider, or longer, but its > nominally .9 by 1.75" now. Where I have them mounted, width could go up > an inch w/o impinging on the rest of the stuff in that box. > > With that amount of gain in the buffering, I doubt if any schmidt > triggering hysteresis would be needed to get a clean switch. About a .05 > u-f feedback capacitor from the output back to cF to speed it up would > be a great plenty I'd think. > > Food for thought and experimentaton when I am next bored. But its > working with the big current limiting resistor now, and its only heating > 2 or 3 degrees per on/off cycle to do it, so my natural tendency toward > lazyness and to not fix what isn't broken will likely detour that > effort. Sad, but as a former Bro-in-Law used to say, its good enough > for the girls I go with. :) > > But I'd like to get this furniture project done & delivered while I take > a grand tour to Nebraska & Kansas to deliver 3 of them to my son's > sometime this summer before I fall over. And get a couple small 45 > degree dovetail mills ordered so I can hack out a teeny QC mount for > this endoscope camera. Then I can do double sided PCB's without all the > foolishness changing the tool out for a sensing contact to locate a hole > in piece of brass tubing set into the corner of the pallet & calculate > all the offsets needed to do the back side of a board. That got quite > tedious on the toy mill too. > > Snooping around on fleabay last night I found this: > > < > http://www.ebay.com/itm/1-PC-3-8-X-45-DEGREE-PREMIUM-HSS-DOVETAIL-CUTTER-MILLING-HIGH-SPEED-STEEL-/131511946248?hash=item1e9eb90c08:g:JmcAAOSwBahVVON- > > > > Which looks like a decent price, but the pix doesn't match the > description, so which is correct? If its as small as it claims, it > would be ideal. I thought of hitting the buy it now for 4 of them since > they are HSS and would need to be drowning in cutting oil. Should I? > > 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> > > > ------------------------------------------------------------------------------ > Site24x7 APM Insight: Get Deep Visibility into Application Performance > APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month > Monitor end-to-end web transactions and take corrective actions now > Troubleshoot faster and improve end-user experience. Signup Now! > http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
