Quote:
Originally Posted by Daniel Bathgate
I see your point, but 1 atm pressure is hardly arbitrary (in our standard atmosphere-based game, at least). The gas laws indeed work the same, but negative signs tend to make things practically different. I can't say I personally know much about pneumatics or vacuums, though. Hey, come to think of it, could you use a standard solenoid connected backwards with a vacuum? That might be interesting (and perhaps FIRST illegal, but would it work physically? I guess it would depend on if the pressure of the vacuum was great enough to actuate the solenoids. Hmm...)
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Yes, you can connect vacuum to a standard solenoid valve (I do in all the time at work), however you need to watch the porting. You need to make sure that air flows in the same direction that it normally would using positive pressure as the valves are generally designed with the spring force and air flow assisting closure of the valve. This means that you need to hook your vacuum source to the requirement port, your vacuum target (suction cup ... etc) to the common port and leave the supply port open to atmosphere.
Quote:
Originally Posted by Daniel Bathgate
Ah. Didn't think of that since we have many extra plugs floating around but ran out of T's. Whatever works! 
Good to know! I remember playing with the suction cup last year and not having it work very well; I was probably pushing all 60psi through the vacuum. I'll remember that. |
The Venturi that you use will have a curve that will tell you your best inlet pressure. Generally the higher the inlet pressure the deeper vacuum the venturi will pull, however the tradeoff is that while the venturi will pull a deeper vacuum it tends to have lower flow at very high input pressures ... thus drawing down the pressure slower.
Quote:
Originally Posted by Daniel Bathgate
I love reading about pneumatics hacks, ever since we kinda-sorta implemented mid positions to try and save our arm last year. Looping the vacuum back through the solenoid is impressively creative... though I wonder if it wouldn't be easier to just hook up a servo to that butterfly valve  |
Parker makes Electronic pressure controllers and cylinders with feedback encoders that allow you to control how far the cylinder throws (infinite mid positions) ... unfortunately that are not FIRST legal
. Oh how I wish FIRST would loosen up on their pneumatic rules.