On Friday, 15 April 2022 15:46:39 EDT Chris Albertson wrote: > 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. > They aren't, they are teeny little diaphram types, and will actually run without any outrageous heat on 5 volts. Lots smaller than a cig lighter powered emergency tire pump. No flywheels at all.
> 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. What I'm trying to do is run the mister on the 6040 mill without burning up the 2 horse shop compressor to make 120+ psi, then regulating it down to 3 or 4 lbs to feed the mister. This runs at the full 12 volts, making more air than needed to run the mister, and does it about 65 db quieter than the shop compressor. It'll also serve to blow the sawdust away while making a new screw for a woodworking bench vice. If it works well, I might even run an ad in Fine Woodworking. I haven't seen anyone else adv them in 15+ years. Yup, I've clearly got too many hobbies... > 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 <[email protected]> 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 > > [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 > . 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
