Post by thread:Re: Air pressure regulator

I just started learning PIC controllers. I have a number of ideas brewing. The first is a digital air pressure regulator. Sounds really easy to me. I want to be able to turn a dial and have the limit displayed on a 7 segment led. I also want the limit displayed without actually having the pressure in the system, so a sensor reading line pressure is not appropriate. A quick A/D and either a stepper motor connected to a manual regulator or I was thinking of a rotory encoder to give a position of the air reg. screw and then interpolating this into a digital readout, Or perhaps I could read actual spring pressure on the diaphram? Or something else The something else is what I would like some input on. I plan on the 16F84 as I have info on it. Any/all input appreciated. TIA Pat Roberts

In message <spam_OUT3488E723.67FDTakeThisOuTbc.sympatico.ca>, patrick roberts <patrick_rob .....ertsKILLspam@spam@BC.SYMPATICO.CA> writes >I just started learning PIC controllers. I have a number of ideas >brewing. > >The first is a digital air pressure regulator. Sounds really easy to me. >I want to be able to turn a dial and have the limit displayed on a 7 >segment led. I also want the limit displayed without actually having the >pressure in the system, so a sensor reading line pressure is not >appropriate. > >A quick A/D and either a stepper motor connected to a manual regulator >or I was thinking of a rotory encoder to give a position of the air >reg. screw and then interpolating this into a digital readout, Or >perhaps I could read actual spring pressure on the diaphram? Or >something else > >The something else is what I would like some input on. Not much to do with the above, but I'd like some comments. I'm experimenting with air muscles, and need a reservoir and regulator system to hold the air pressure from a little 12 V tyre compressor to about 3 bar. I'll probably use something really crude like a mechanical tyre pressure gauge shutting down the compressor when the pressure limit is exceeded. That just gave me an idea! I'll use a scooter wheel inner tube as the reservoir! Leon -- Leon Heller: leonKILLspamlfheller.demon.co.uk http://www.lfheller.demon.co.uk Amateur Radio Callsign G1HSM Tel: +44 (0) 118 947 1424 See http://www.lfheller.demon.co.uk/rcm.htm for details of a low-cost reconfigurable computing module using the XC6216 FPGA

Leon Heller and Patrick Roberts write: <snip #1> > >The first is a digital air pressure regulator. Sounds really easy to > me. > >I want to be able to turn a dial and have the limit displayed on a 7 > >segment led. I also want the limit displayed without actually having > the > >pressure in the system, so a sensor reading line pressure is not > >appropriate. > > > >A quick A/D and either a stepper motor connected to a manual > regulator > >or I was thinking of a rotory encoder to give a position of the air > >reg. screw and then interpolating this into a digital readout, Or > >perhaps I could read actual spring pressure on the diaphram? Or > >something else > <snip #2> > I'll probably use something really crude like a mechanical > tyre pressure gauge shutting down the compressor when the pressure > limit > is exceeded. That just gave me an idea! I'll use a scooter wheel inner > tube as the reservoir! > Guys, what you need already exists!!! Its called an E/P or I/P converter. It takes a voltage or current input and adjusts itself to provide a gas (air) pressure output (you also supply unregulated air). These are made by Moore Products, Inc and Moore Industries. They're two totally separate companies who just happen to make similar products. The "off the shelf" model is a 4-20 mA current loop input with 3-15 psi output @ 1.4 SCFM (other ranges available). So long as you do ask for more volume than it can supply or apply back pressure, the output is linearly proportional to applied current (voltage). I think price from Moore Industries is around $250 IPT-DIN. Accuracy better than 1%. Simply set up a PIC to provide your analog driving signal and display/set functions. If you need a much different output range then use the I/P to drive a pneumatic amplifier/attenuator (has span/offset adjustments) so that 3-15 psi can be scaled to do say 0-100 psi. Moore Industries 16650 Schoenborn St. Sepulveda, CA 91343-6196, USA (818) 894-7111 (800) 999-2900 Sorry, I don't have a current address for Moore Products. I would not recommend trying to do a motor drive on a manual regulator without a pressure transducer for monitoring the output. You just won't know for sure where you're at. I would not trust simply being able to turn the adjusting screw and get the same pressure every time (but this does depend on your tolerance). You'll need quite a bit of torque to operate one anyway. Your garden variety regulator requires some amount of air flow in order to regulate. Hope this helps. -Frank