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CHEAP air cylinder positioning with 43oh and flow meter

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Hi Guys! I've been toying with an idea, that I  didn't think would work, and set up a test jig.

Using an air compressor, a solenoid valve, a flow meter and a 43oh I found that we can get a repeatable cylinder position, like +-2.5 mm! 

The flow meter is measuring the volume of air that we've fed to the cylinder and the 43oh opens or closes a solenoid valve depending on the cylinder position.http://arduinoforgoodnotevil.blogspot.ca/2013/10/accurate-ish-pneumatic-cylinder.html


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Glad you like! More fun in the works!


No, this came out of a gold mining machine. I'm re-purposing for something completely useless. ;-)


As for varying loads, yes and no. 

If you are talking lifts various weight of items, shouldn't make a difference because the cylinder volume is constant. You put in 3 litres of compressed air @ 30psi, the cylinder moves 500mm. You put in 3 litres of compressed air @ 200psi, the cylinder moves 500mm. The trick is, the 43oh needs to return to a known position (full retract, full extend, or limit switch) prior to changing the load.


But if the load varies with stroke, like a pivoting boom, then there needs to be some fancy maths to figure it out. Because air is compressible, the 3 litres you put in @ 30psi gets compressed as pressure required to support the load increases.


And, it'll be sloppy because air acts like a big spring under accelerating and decelerating loads.

But I've got a few tricks up my sleeve to deal with that...

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