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I am looking for a component which can help me controlling the pressure in a tube.

I explain :

I have a compressor which blow some air in a tube. The compressor blow up to 8 bar and the tube is really small. I need a pressure between 1.5 and 2 bar in the tube. Then I am looking for a component, that I can drive electronicaly, which can do that for me.

Does anyone know about this type of component?

I don't know if I am clear, if you need othr information I'll edit my question.

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  • \$\begingroup\$ This has nothing to do with electronics; it's a mechanical problem, even if the device is electronically controlled. The question will most likely be closed as off-topic. \$\endgroup\$ – stevenvh Oct 11 '12 at 9:18
  • \$\begingroup\$ It's completely an electronic problem. I don't ask for the mechanical description. I just ask if anyone know an electronic component which can do what I ask. \$\endgroup\$ – damien Oct 11 '12 at 9:36
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    \$\begingroup\$ If you have an actuator (a compressor), and a sensor (pressure sensor), and only if both have an electronic interface, only then this becomes an electronics problem. Suddenly this simple question becomes a big project. You'll likely need a bunch of op amps, a PWM generator, maybe even a microcontroller, a few transistors, a relay, and a lot of work. You'll have more luck googling someone's blog with a project description and code than expecting someone to do it all for you here. \$\endgroup\$ – Jonny B Good Oct 11 '12 at 9:55
  • \$\begingroup\$ I may have been not clear you're right, I have a microcontroller, some relays, some transistors... on my project I am just looking now for a component that I could drive from the microcontroller and which would help me controlling the pressure in the tube \$\endgroup\$ – damien Oct 11 '12 at 10:00
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    \$\begingroup\$ You'll probably need to use an electric valve and a digital pressure sensor together to achieve your goal. \$\endgroup\$ – Garrett Fogerlie Oct 11 '12 at 10:18
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Such components certainly exist. They tend to be called I to P converters (current to pressure). I.E. you give them a signal in the form of a current, and they will regulate the air pressure according to that current.

Electronic pressure regulator

If you're in the UK, you can buy them from Airlines Pneumatics. Using one of these will solve your problem immediately, but they can be expensive.

The alternative way to solve this problem is to control the pressure yourself. Since you already have a microcontroller, then you just need a pneumatic valve and an air pressure sensor.

Valves come in two basic types, proportional (you have fine control over the on percentage) or digital valves (which are either just on or off). I recommend a proportional valve if you can afford it, and if you can be bothered to make the electronics to drive it. This valve from Sirai is quite nice:

Sirai proportional valve

By regulating the current through it, you can control how open it is, and thus the rate at which air flows into your tube.

Next you'll need a pressure sensor.

Pressure sensor

Measure the pressure (preferable at the other end of the tube to avoid various pneumatic effects caused by the moving air, like Bernoulli's principle, where the sensor will see a false drop in pressure as the air flows past it towards your tube.

Once you have your valve and sensor, the microcontroller can control the valve to control the pressure. I recommend something simple like a pure P controller.

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  • \$\begingroup\$ Depending on the pressure accuracy required you may need to include a bleed. The off the shelf I to P controller probably has this built in. The do it yourself will need a bleed. Without a bleed the pressure will overshoot your target pressure and latch. \$\endgroup\$ – docscience Feb 1 '15 at 5:12
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What you are asking is definitely possible. In fact, I have done it with one of these solenoid-controlled proportional valves. Basically I used a dsPIC to measure the output pressure, run a PID control algorithm, and adjust the PWM that drives the solenoid to regulate the output pressure. And yes, it worked very nicely, much better than older mechanical regulators. Having the processor there also made it possible to control and report pressure digitally over several communication interfaces.

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  • \$\begingroup\$ Hey, those are cute little valves! \$\endgroup\$ – Rocketmagnet Oct 11 '12 at 20:34

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