There is another way to isolate an analog control. Use an LDR. A light-dependent resistor. These act like normal resister but change value depending on how much light is shining on them. Ages ago in the 1960s people would package them in a tube with a light bulb then you have an optically isolated analog path. They are non-linear so this has to be worked around. Just like a modern "opto" but they have an analog path. You can still buy these.
There is a very old vacuum tube-based piece of recording studio gear that is called a CLA-2 compressor/limiter. It will keep the output volume constant even as the input gets louder or softer. There are two parts to this unit, one measures the input level and adjusts the brightness of a tiny light bulb the other half is an adjustable gain amplifier where the gain is controlled by the LDR resistance. These were used in AM radio stations, ball-park PA systems, and likely 100 other places. I use a digital simulation of this device if I record voice-over for video. Cranked up, it makes even me sound good. I've been wanting to build a reproduction using real tubes for a long time but the simulation works so well. (Another hobby is vacuum tube electronics.) That said, optoisolated PWM or optoisolated serial seems more of a 21st-century solution and is cheap enough. Thanks. On Mon, Jun 1, 2020 at 8:21 AM John Dammeyer <[email protected]> wrote: > > From: Gene Heskett [mailto:[email protected]] > > > > On Monday 01 June 2020 08:25:12 Dan Henderson wrote: > > > > > Chris, would think you would be able to connect the 0-10v output from > > > a BOB directly to the controller middle leg output of the > > > potentiometer. You wouldn�t need the hot leg, but would likely need > > > to ground the bob to the controller. > > > > > And that will break the mirror and let out all the smoke this stuff runs > > on and then none of it works. Certainly blowing the bob, possibly the > > computers port and various bits and pieces in the computer because the > > hot side of the line will then be connected to the computers ground. > > And, although compared to the MESA board, these are really cheap, as > Gene and Andy have stated this too doesn't have optical isolation. So it > works fine with my Bergerda AC Servo but won't with the mini-mill without > first optically isolating the PWM input and using an isolated 15V power > supply. > https://www.aliexpress.com/item/33021792064.html > > By the time you've done that the MESA is probably a better deal. > > > http://store.mesanet.com/index.php?route=product/product&product_id=205&search=SPIN > > John > > > > > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
