Current to pressure converter

[nomadicbrew]

I just want to make a very basic current to pressure converter to be demonstrated in school. How Can I do it? Input should be in ma DC and out put to be somewhat proportional to the input. Not much accuracy needed.

 

[stevez]

I would recommend you do a little research on I/P transducers - very common over the years as a way of converting 4 to 20 ma current loop to 3 to 15 psig or similar pneumatic output.

I - current
P - pressure

I/P, I to P,

You might discover how it's been done commercially and work your way back.

If you have an air supply you can construct a means to vary the pressure - you have a tiny control valve - a needle valve that allows an amount of air to flow - near the discharge is a small orifice that bleeds some of the air - the balance goes to the load. The pressure is varied based on needle valve position. You might operate the needle valve with a coil that responds to current flow.

 

[mneary]

Is your output a barometric pressure or is it a force?

 

[Leftyretro]

I just want to make a very basic current to pressure converter to be demonstrated in school. How Can I do it? Input should be in ma DC and out put to be somewhat proportional to the input. Not much accuracy needed.

A I/P transducer is not a simple project as it is by nature a electromechanical component, however you can buy nice quality used devices on E-bay.

If you want quick and easy DIY, take a radio control type servo (they come in several sizes to match whatever torque you will need) and mechanically attach it to a 1/4 turn ball, "two way", valve (3 ports). The common valve port tubes to your pressure source and the other two ports are the output pressure and the vent port. If you are dealing with only pressure control and don't need much flow then a small 1/4" or smaller valve will work fine. If you need substantial flow then you will have to size the valve and pressure source to support the flow required.

You can either use open loop control by mapping servo position Vs output pressure and use the map as a look-up table in a small micro-controller chip or PC control program.

If you wish closed loop control then you will need to have a pressure sensor hooked up to the valve output port and use a controller program to control the valve position to match the desired pressure (setpoint value) using the pressure sensor as the error sensor. Search google on PID control for algorithm information.

Good luck


Lefty