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
