It sounds like maybe you are trying to run the compressor at a speed so that it provides the desired pressure and volume without using an accumulator tank. This means running the compressor at low RPM and high torque continuously. Have you checked that you can do this? My guess is that you'd burn the compressor motor up. Try it with a variable voltage bench power supply and see if the motor can run slow for 30+ minutes. Most compressor motors need to use a flywheel and those don't work well at low speed unless they are really big.
But then I read you have a range of tiny compressors. If so then you solution is to control each one with an on/off bit and the total power is the number of compressors actually running. Most people use an on/off switch for the compressor and then a mechanical regulator. If you need variable pressure under computer control then motorized the mechanical regulator, or two regulators and a valves to select high/low pressure. About that high voltage op amp. If you need to measure a high voltage scale it first with a 10:1 voltage divider. It is cheap and very accurate. If the problem is the op amp needs to output high voltage then have the op amp drive the base of a bipolar transistor and then run the transistor's output around to the opamp's other input for feedback. (after scaling with a voltage divider.) the transistor might not be linear but the feedback corrects this. On Fri, Apr 15, 2022 at 11:41 AM gene heskett <ghesk...@shentel.net> wrote: > Hi Peter; > > It looks as if the inavailability of the high voltage op-amp I was going > to use will make me use just a part of the a/d range of a 7i76D first 4 > inputs. > > And, the relative lack of data for the MAP sensor I have two of, might be > a limitation too. The data is sparse, but what has me thinking is the > maximum current available at its output is shown as .1 milliamp, at full > scale which would roughly correspond to around 23 psig, or 38 psia, which > is what its actually measureing. And I want to regulate the pwm to a > bank of teeny conpressors that can do at least 10 psig, to around 4 or 5 > psig. So rangewise its doable. > > Since the max output currant is .1 milliamps, and I need to subtract > ambient pressure from whatever I measure when the conpressors are off. > This isn't super critical and its something I can do in the setup for the > program. > > So my question then is how big a load is the a/d when doing the a/d for > for a 2 to 3 volt signal from the MAP sensor? > > Thanks Peter. > > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
