I was thinking about a pneumatic configuration where TWO single action solenoids were hooked up to ONE dual action piston. My hope is to produce 3 possible states. Extend, contract and open (off/off). Has anyone tried this before? I don’t have any hardware to test with and wanted to know if there were any problems with this setup before dropping several hundred dollars…
The middle state should be on/on, otherwise you’ll end up moving with whatever payload you have, but no, it should work, make sure to wear safety gear before trying, as the pistons pressurized at 100 psi in 1/2 the space as nesecary, but you should be fine. (Also dont buy single acting stuff, you can acomplish the same things with double acting stuff) also, you can buy singular solonoids at robotsource so yiu donr have to spend as much
I think he really wanted off off. Its a configuration that allows compliance. It has been done before. Most famously by 12A in sack attack. They used it because they had a 4 piston intake and could only power 2 of them if they only needed half power strokes. The other pistons were left off to conserve air.
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And thinking about it I don’t think on/on would work at all. They would be connected to the same air supply.
This wont work the way your thinking it will. If you have equal pressure on both sides, then you end up with zero force and the piston won’t move on its own. This means that if you set the piston to off/off or on/on, it will remain at whatever it’s current position is but lose all power. I experimented with this before.
If you want a third position in the center, one solution is to place two counteracting rubber bands/springs on the piston, since rubber bands and springs do not provide constant force (F=kx), they will reach equilibrium in the center. However this configuration does not work too well as your air gets depleted (the fully extended and fully retracted positions will gravitate towards the center as you lose pressure).
Another solution is to use a second piston at a higher pressure then the first as a limiter, when the second piston is off, the first can fully extend and retract, when the second is engaged, the first is limited to only half of its range. This is the configuration we used in our 3 speed transmission.
This is possible. We did something similar on our FRC robot this past season. We had a double action cylinder connected to two single action solenoids. With both off the flap that the cylinder was moving was able to freely pivot. Then whenever we wanted to use it we would either activate one solenoid or the other. We ensured in code that both solenoids were never on at the same time.
Assuming you’ve used double acting solenoids, no exhaust flow controls, and the second port of each solenoid is open to the air, in the first “state 2” the air cylinder will be free-floating. The air cylinder will be pushed to approximately the center position by the rubber band, but will not be held fixed in that position. In the second “state 2”, the cylinder will not move, unless the rubber band is attached to the cylinder rod to pull it back out to approximately center.
A more reliable 3-state situation is created by attaching two cylinders together back-to-back in a straight line. State 1=both cylinders retracted, State 2 = one cylinder extended, State 3 = both cylinders extended. We use this setup in industry, and Bimba actually make a 3-position cylinder like this (not VEX legal)
Original Line® 3-Position - Original Line 3-Position - Norgren
shoot yep sorry