On Sunday, 29 May 2022 01:56:23 EDT Chris Albertson wrote: > So you want to be able to control the air pressure from within LCNC? > One way is to have LCNC output a desired pressure then the air > compressor just does what it is told. Use a $4 microprocessor (even > an Arduino would work) to read the I2c and also read some output from > the Mesa card. The Meas could just set a bit to control on/off or use > PWM to send a desired pressure value > > The pressure regulation could be done by the compreoor
More hardware I'd need to learn to program. Why bother when hal can do it? hal can do all that. And I've been manually (from the axis gui) controlling the peristaltic pump that delivers koolmist to the mister for a couple years now, so adding another circuit in hal to throttle the pwm to the compressor driver is for me, quite trivial. The sum2 module can do the math. It should have been named math2. The name sum2 hides its real abilities. It can do all 4 functions of a $6 calculator. hal has the tools, they are in the toolbox so why not use them? pyvcp can even show me the actual pressure in the gui if I can figure out how to calibrate it. The biggest problem I can see is nuiquist related due to the somewhat springy use of air screwing with the response time. hal can do that too, its called a limit3, so I'd imagine I'll have to limit the rate of change out of the sensor to keep it from oscillating. With the sensor watching the output manifold, and 5 compressors running out of synch, the pulsations in pressure will be far more than the average, which is what I'm after. The lag in the i2c seriel channel of the sparkfun device will add considerably to that tuning difficulty. > On Sat, May 28, 2022 at 10:33 PM gene heskett <ghesk...@shentel.net> wrote: > > On Sunday, 29 May 2022 00:21:48 EDT Chris Albertson wrote: > > > This would be the sensor I would use. The link below is a very > > > detailed gud that tells you how to use the sensor, including > > > working > > > example software. > > > > > > https://learn.sparkfun.com/tutorials/sparkfun-qwiic-micropressure-h > > > ooku p-guide > > > > I've looked at that but I need an analog output I can op-amp up to > > the > > swing range I need. Mesa doesn't have an i2c interface that could > > talk > > to. I have some honeywell gage mode analogs coming from Mouser in > > that > > price range which can tolerate up to a 12 volt vcc, and that will > > help > > the noise budget considerably. But they won't ship till Teusday. > > > > > Yes, it is an absolute sensor but air pressure on Earth does not > > > change that much/ If you really care a lot then use two pressure > > > sensors, leaving one open to the ambient air. (But that would be > > > over the top, nuts for an air mister) > > > > Agreed, just an offset to cancel the first 14.7 psia should work fine > > too. > > > > > The interface is easy to use I2C using the pseudo-standard "QWIIC" > > > connectors (physically JST connectors) The documentation is makes > > > using this easy. > > > > But where do I find an i2c fed D/A? I didn't note such a beast at > > Lady > > Ada's place. > > > > > On Sat, May 28, 2022 at 8:44 AM gene heskett <ghesk...@shentel.net> > > > > wrote: > > > > Greetings all; > > > > > > > > I'm getting frustrated, but I know it has to be out there, > > > > someplace. > > > > I need a differntial air pressure sensor, differential so it > > > > references local barometric as its reference zero, and up to 10 > > > > psi, > > > > with a 3 wire analog output. > > > > I've solved the control aspect, but not how to detect a pressure > > > > to > > > > accomplish the control. > > > > > > > > automotive EGR types seem seem the most promising as they are > > > > affordable and 2 port gismo's but all I can find just lists the > > > > vehicles it fits and works with, but zero info on how to hook it > > > > up > > > > and get an analog reading out of it. "MAP" sensors whose > > > > internal > > > > reference is a good vacumm can have their signals clipped and > > > > massaged into something usable, but so far I've bought 4 w/o > > > > finding > > > > a working one that actually reads the 14.7 psia of normal air. > > > > > > > > So how are you folks solving that problem? > > > > > > > > Or are you burning up the shop compressor feeding your misters? I > > > > can't see that as being an acceptible solution since none of > > > > those > > > > have an intake muffler so you can still hear yourself think. > > > > > > > > What I have cobbled up at the moment is giving me more than > > > > enough > > > > air to run a mister, and I can't hear it running over the 2 fans > > > > in > > > > this 6040 mill. One in the vfd is really noisy. > > > > > > > > Thank you. > > > > > > > > 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, 1940) > > > > If we desire respect for the law, we must first make the law > > > > respectable.> > > > > > > > > - Louis D. Brandeis > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > Emc-users@lists.sourceforge.net > > > > 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, 1940) > > If we desire respect for the law, we must first make the law > > respectable.> > > - Louis D. Brandeis > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > 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, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
