Hi, Just did a super quick google search and came up with a fairchild optocoupler hcpl2530 that will do 1Mbps. ~1.80 USD quantity 1. Isolation to 480v and good common mode rejection. There are a number of devices in similar and better speeds.
That's not anywhere near the top speed for laser/detector systems, which now run to 100Gbps and beyond. opto stuff is so much cheaper than it used to be. The combination of insane laser volume and the demand for ultra speed detectors have made fast stuff really cheap. jerry On Mon, Dec 14, 2015 at 1:57 PM, Gene Heskett <[email protected]> wrote: > On Monday 14 December 2015 16:01:26 Ben Potter wrote: > > > > Note that those setup and hold times are relative to the riseing > > > edge of > > > > the (step?) pulse, and the next line is not so specific, but I expect > > it needs to be checked by a dual trace scope for both > > > > > conditions > > > > I'm very tempted to pull the G540 from the router and rig up a test > > bench test to see if I can get my head around why this is happening. > > Might get time over christmas. > > > > Would be nice to know why inverting the step output works for me, > > rather than 'it just does' I'm starting to suspect that the 5i25 obeys > > the set timings, whereas mach on a parallel port uses them as a > > minimum guide, and frequently exceeds them. > > > > > > I have no additional opto-isolation in that path - I believe that > > > > the G540 uses fast opto's on all the parallel port pins (from the > > > > manual, I'm sure there was a post on cnczone detailed the choice > > > > of isolater somewhere) > > > > > > Thanks for that , so it would have been DIRSETUP/DIRHOLD that I was > > > > concerned with. > > > > I managed to dig out the thread where Mariss of Gecko was talking > > about opto circuits. > > http://www.cnczone.com/forums/general-cnc-machine-related-electronics/ > >23216- optoisolator-circuit.html > > > > Posts #2 and #6 are particularly interesting (not sure on cross-post > > etiquette here), and possibly give a hint as to the root cause of my > > problem. > > > > > > <snip> > > > > > > And that gives you far finer tools to tune with than software > > > stepping > > > > ever will. There may better interfaces than the 5i25, but for us > > stepper people, its the cats meow. Not bulletproof on its inputs, I > > didn't have a good enough > grounding setup wrapped around my G0704, > > and apparently blew the input I was using for a probe. > > > > > I don't know as Peter could tell me which chip to replace to rescue > > > it. I > > > > AM a C.E.T. and in my dayjob before I retired in 2002/6/30, I could > > have done it easily, but at 81, my hands aren't as steady as they once > > were. > > > > They do pretty nicely on servo stuff too - I have a 5i25 on the > > (servo) bridgeport, the (stepepr) lathe was converted earlier, and > > that has a 5i20 on. > > > > > I can't comment based on experience with them so I won't, Ben. > > > Other than > > > > to say that 98% of the opto stuff out there, will need a pulse in > > excess of 1 microsecond on, and often pushing 2 u-s to turn off. I > > understand there are > > > > > some Gas based optos about, but they'd have a serious effect on a > > > BoB's > > > > price. One could turn a $15 BoB into a $100 BoB pretty fast. > > > > From the thread above it looks like Gecko use the HCPL-2531 in at > > least some of their drives - price of $0.87 per 1k doesn't look too > > bad for a fast dual channel opto. > > > > > However, one must bear in mind that when looking at it with a scope, > > > we > > > > are watching the voltage, and in opto stuff, voltage doesn't mean near > > as much as actually measuring the current. Why? Because when the > > > > > driving led in the opto goes out, which it might do at 1.85 volts or > > > as high as 2.4 volts, the load is gone, leaving the voltage to decay > > > > toward (which ever rail its headed for) at a very leasurely rate. > > > > > Thats a fancy, CMA way to say the scope is lieing to you. So I tend > > > to > > > > look at the decay with an eye toward seeing if I can define that point > > where the down (up?)ward curve changes to a slower rate, then make the > > "on time" timing > measurements to that point. That can be a difficult > > point to define even for me, and I've "had a scope probe in one hand" > > > > > for 64 years. 64 years ago it was a 5mhz Hickock, today I have > > > 100MHZ dual > > > > trace analog, and 200mhz dual trace digitals to go poking around with. > > > > > Cheers, Gene Heskett > > > > Good to know, I have a rescued tektronix scope which I rarely get to > > use. Hints on those things that are only learned through experience > > are always appreciated. > > > > I suspect spotting most of the ways phase shift can trip you up even > > on simple circuits takes quite a bit of practice. > > > That, and ingenuity in figuring out how best to get at it with a probe. > And sometimes you can't, you have to go well beyond and let experience > guide one on figuring out what the heck is going on at the point of > interest. I have even written software to excite the circuit, then asked > it to play it back, then do a comparison of sent vs echo. In this case, > a 4x4 fifo, used 2 wide for an 8 bite wide rubber buffer coupling in a > video switcher, had one of the 2 4x4 fifo's that wasn't responding to > the shift out command, about 2% of the time. Called the switcher maker, > who wanted $1500 a copy for the chip. But I'm sneaky, I suspected it > was an AMD product, called them, and they said yeah, we finally did get > a JEDEC number for it, and its $2.10 a piece, how many do you want? I > took a mental inventory of how many were in it, and ordered 2 sticks, > then told the GM there would be a COD package from AMD. He had his > usual litter of cows. I had no sympathy. When he finally got caught > playing with the books, I told him as he was forcibly leaving in the > company of a deputy, to be carefull and not let the doorknob hit you in > the ass. > > Good guess, I was out of them when they finally decided it was time to > retire the beast for other reasons. It had a higher failure rate. None > of the newer ones ever failed, just the OEM's. I believe there were 48 > in it, and something over half of them failed in the next decade. > > Great switcher in terms of capabilities, advancing the state of the art & > sold new for about $300k. We used up the one from the JCPenny > production house in NYC, then finished off the one KTLA bought new. > > But that was another time & place compared to now. :( > > > Thanks > > Ben > > > > > > ---------------------------------------------------------------------- > >-------- _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > 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 > -- Jerry Scharf FINsix IT 650.285.6361 w 650.279.7017 m ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
