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Unread 18-02-2006, 01:12
TubaMorg TubaMorg is offline
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Re: HELP! We need pneumatic wiring help!

Yes the above post is correct, however this valve alone isn't enough to stop a cylinder stroke midway. You should use another double solenoid valve so that one valve controls the air into the cylinder and the other valve controls the exhaust. You see you need to lock the air in the exhaust side to stop the cylinder mid stroke. Check out this post:

http://www.chiefdelphi.com/forums/sh...ght=pneumatics

Post #11 has a simple diagram that shows you how to do it.

Good luck!
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Unread 18-02-2006, 07:44
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by TubaMorg
Yes the above post is correct, however this valve alone isn't enough to stop a cylinder stroke midway. You should use another double solenoid valve so that one valve controls the air into the cylinder and the other valve controls the exhaust. You see you need to lock the air in the exhaust side to stop the cylinder mid stroke. Check out this post:

http://www.chiefdelphi.com/forums/sh...ght=pneumatics

Post #11 has a simple diagram that shows you how to do it.

Good luck!
This is how CHAOS has done it in years past with positive results.
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Unread 18-02-2006, 08:50
BrittanyV BrittanyV is offline
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by TubaMorg
Yes the above post is correct, however this valve alone isn't enough to stop a cylinder stroke midway. You should use another double solenoid valve so that one valve controls the air into the cylinder and the other valve controls the exhaust. You see you need to lock the air in the exhaust side to stop the cylinder mid stroke. Check out this post:

http://www.chiefdelphi.com/forums/sh...ght=pneumatics

Post #11 has a simple diagram that shows you how to do it.

Good luck!
I'm pretty sure that this valve alone is enough. We had it on the bench and we were stopping the piston halfway through with the orange buttons.
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Unread 08-03-2006, 17:29
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by BrittanyV
I'm pretty sure that this valve alone is enough. We had it on the bench and we were stopping the piston halfway through with the orange buttons.
You need two valves. One for direction, which you hook up normally. Then you connect the vents from the first valve to a second, to stop the air from venting to the atmosphere. This stops the cylinder from moving until this second valve is opened.

Program the first for direction, the second for movement(on/off)
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Unread 09-03-2006, 19:17
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by Dad1279
You need two valves. One for direction, which you hook up normally. Then you connect the vents from the first valve to a second, to stop the air from venting to the atmosphere. This stops the cylinder from moving until this second valve is opened.

Program the first for direction, the second for movement(on/off)
This will work fine. Last year we found a better solution, called a "Three-position pressure center" valve. The spec sheet is here. Look at valve type SY3520-6H, for example.

This kind of valve has three positions, and uses two solenoids: Position 1 is extend, Position 2 is hold, and Position 3 is retract. One solenoid is Extend, the other is Retract, and when neither is energized it means Hold. (This can and should be controlled with a single spike as explained by coffeeism above).

We selected "Pressure Center" types, which apply full pressure to both sides of the cylinder when in the Hold position. You can also choose "Closed Center", which closes off all air to the cylinder. You don't want "Vent Center", which will allow the piston to move freely in the "Hold" (center) position.

One important thing we learned last year: Pistons work best in 'this end or that end' applications - they do not work well for non-endpoint positioning. The problem is that any variation in load causes the piston to move, because it's only air, and that will often cause a problem.

Good luck. I hope this post helps anyone considering midpoint positioning of pneumatic cylinders.

Don
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Unread 09-03-2006, 23:08
TubaMorg TubaMorg is offline
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by Don Rotolo
This will work fine. Last year we found a better solution, called a "Three-position pressure center" valve. The spec sheet is here. Look at valve type SY3520-6H, for example.

This kind of valve has three positions, and uses two solenoids: Position 1 is extend, Position 2 is hold, and Position 3 is retract. One solenoid is Extend, the other is Retract, and when neither is energized it means Hold. (This can and should be controlled with a single spike as explained by coffeeism above).

We selected "Pressure Center" types, which apply full pressure to both sides of the cylinder when in the Hold position. You can also choose "Closed Center", which closes off all air to the cylinder. You don't want "Vent Center", which will allow the piston to move freely in the "Hold" (center) position.

One important thing we learned last year: Pistons work best in 'this end or that end' applications - they do not work well for non-endpoint positioning. The problem is that any variation in load causes the piston to move, because it's only air, and that will often cause a problem.

Good luck. I hope this post helps anyone considering midpoint positioning of pneumatic cylinders.

Don
Whoa! Correct me if I'm wrong, but I thought the use of "alternative" solenoid valves is prohibited! How'd you get away with that? Of course there are valves out there that can control mid-stroke positioning, but we are only allowed to use the solenoids in the kit. You are right, though, that the compressability of air makes positioning pretty iffy...definitely no precision there without a more complex feedback mechanism (such as a pot).
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Unread 10-03-2006, 09:26
Dad1279 Dad1279 is offline
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Re: HELP! We need pneumatic wiring help!

Quote:
Originally Posted by TubaMorg
Whoa! Correct me if I'm wrong, but I thought the use of "alternative" solenoid valves is prohibited! How'd you get away with that? Of course there are valves out there that can control mid-stroke positioning, but we are only allowed to use the solenoids in the kit. You are right, though, that the compressability of air makes positioning pretty iffy...definitely no precision there without a more complex feedback mechanism (such as a pot).
I thought the same, but a quick search of last years rules seems to allow it.

I will disagree about the positioning, however. We used it to lift our main arms last year, and it worked well enough to seed 1st at VCU and 2nd NJ Fast, strong, simple and precise enough to lift and position the tetras.

However everything has a place, and this year we use no pneumatics.
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