On Sunday 13 October 2019 19:46:55 Kenneth Lerman wrote: > Hello All -- especially Gene, > > I've seen many posts on the lists regarding breakout boards and > dealing with issues regarding slow opto-isolators. I have a question: > > Is anyone using: ISO776x > <http://www.ti.com/lit/ds/symlink/iso7760.pdf> devices?
I've seen that pdf before, but in the cases where I've simply bypassed them, I had good solid, noise free sources to start with. If I use a BoB, its a Saintsmart, simply because there is not any opto's in their output path, and most outputs goto the input opto's of a stepper driver, which I've found is a bit faster than the average bear. A 2M542 for instance can, if the drive is good rail to rail stuff, be driven to about 375k steps a second before it miss-behaves! That will turn a nema-23 motor rated for 270 oz/in, to over 3000 rpms if the supply voltage is pushing the 2M542 at around 42 volts. Nearly 2000 revs at 28 volts. I suspect the reason they aren't used may have something to do with the cost, or possibly the fact that they are capacitively coupled and very low re-rate signals might drift back to their default state, without any change in the input voltage. But thats, to me, just a SWAG. The most glaring example of too slow in my stuff is the 1000 line encoder sitting on top of the G0704 spindle motor, an ABX encoder, and the resultant "scale" is over 14,000 in the .ini file, and thats way too fast for an opto. So I have 2, $2, rs485 convertors to make single ended rail to rail logic out of the encoders differential outputs, Those 2 single ended signals are now being fed to a sainsmart bob whose optos I have bypassed, and on to the 5i25. Works perfectly. I have switches on the gearshift knob that tell my .hal file which gear its in, or no gear in case its between gears, in which case I feed the pid just enough offset to make the motor spin maybe 25 rpm when its out of gear, making gear shifts slick and painless while its running! When its in gear by the last degree and one of the switches is closed, the circuit then scales the "scale" by the gear and restores the speed input from lcnc, and 200ms later the spindle is back up to the set S speed even if its 3000 revs. Thats 800 revs faster than OEM. The 5i25 encoders x input is still the x input from the original optical encoder wheel I made. And with that high a resolution, quantization noise is essentially gone, and I can run the spindle pid's PGain at 40 or so, but 20 is unconditionally stable. With 126 volts in the motor supply feeding one of Jon's pwm-servo amps to that 90 volt, 9.7 amp rated motor, I'm getting close to 2hp at the amplifiers 17 amp limit, rigid tapping in steel with a 3/8's" tap can be done by pecking in steel or cast, going about 1/2 turn per peck. No change in the speed until that 17 amps limit makes its iron chirp. And I'm amazed that the plastic gears in that 2 speed head are still working, by all rights I should have stripped the teeth off them by now. Tough stuff. > They are 100 MHz data rate devices, have high isolation, have six in a > package, and look like they would work just fine. The only downside > might be that they are limited to 5.5 volts on the output, so you > might need to add a transistor driver after them. And all of the ones > in a single package share a ground. > > I hadn't seen them before, so I thought I'd mention them. > They look like they'd be perfectly usable in an active circuit, but I'd have reservations about putting one in a home or limit switch circuit until we find out what their dc characteristics are. > Regards, > > Ken > > Kenneth Lerman > 55 Main Street > Newtown, CT 06470 > > _______________________________________________ > 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
