Controling Pneumatics

[archiver]

Posted by Corvallis at 1/11/2001 7:57 PM EST


Student on team #473, Montana State Robotics, from Corvallis High School.



Ok here is our problem. We need to know how we can get our pneumatics to be able to stop without fully extending or vise versa. In other words how do we control the length of the cylinder by holding down either the trigger or the thumb. As we have it now we press the button once and it extends all the way or contracts all the way. Any help would be appreciated.

[archiver]

Posted by Ed at 1/11/2001 8:06 PM EST


Coach on team #34, DaimlerChrysler/ Bob Jones High , from Bob Jones High / New Century High and DaimlerChrysler/Bob Jones High/ New Century High.


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



"Replumb" the valves and cylinder in such a way as to apply pressure to both ends of the cylinder when it has reached the desired position otherwise one end or the or the other is "exhausting". May take two valves to accomplish this.

[archiver]

Posted by Matt Berube at 1/11/2001 8:24 PM EST


Engineer on team #49, Delphi Knights, from Buena Vista High School and Delphi Automotive.


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



: Ok here is our problem. We need to know how we can get our pneumatics to be able to stop without fully extending or vise versa. In other words how do we control the length of the cylinder by holding down either the trigger or the thumb. As we have it now we press the button once and it extends all the way or contracts all the way. Any help would be appreciated.

Use the limits switchs or the new photo swiths to set the point where you want to stop. Make that switch turn on the air to the oposit side of the cylindar. I don't really know if this will work, haven't tried it.

:=}

Matt B.
T49

[archiver]

Posted by Mike at 1/11/2001 9:42 PM EST


Other from Grandview Heights High School.


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



Differential pressure is one way as noted herein. Your best bet may be mechanical with a toggle. Hit it once and you go. Check for an FPDA distributor in your area at www.fpda.org and go to members. They can help you.

Ok here is our problem. We need to know how we can get our pneumatics to be able to stop without fully extending or vise versa. In other words how do we control the length of the cylinder by holding down either the trigger or the thumb. As we have it now we press the button once and it extends all the way or contracts all the way. Any help would be appreciated.

[archiver]

Posted by Gary Bonner at 1/12/2001 12:43 AM EST


Other on team #433, MINT, from Mount Saint Joseph Academy and Pew Foundation.


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



You can use the pilot operated check valve. Install it on the cylinder port that connects to the normally closed side of the directional valve. Then, the cylinder will extend (or retract, depending on how you have it set up) as long as you're pressing the trigger, and it will stop when you release it. To retract, apply pressure, which would have to come from another valve, to the pilot port of the check valve. This setup unfortunately requires two valves to operate one cylinder. The pneumatics kit would be more useful if it had a better selection of directional valves.

[archiver]

Posted by Joe Johnson at 1/12/2001 9:15 AM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Use the pilot operated check valve
Posted by Gary Bonner on 1/12/2001 12:43 AM EST:



And you know what a gearhead The Chief is!

Believe it or not CD6 will almost certainly have pneumantics. In fact we would like to use more but 3 valves just won't do the job.

Do you think FIRST will allow teams to use more valves? This would be a great change that would make the pneumatics even more useful.

Joe J.

[archiver]

Posted by Gary Bonner at 1/12/2001 11:56 AM EST


Other on team #433, MINT, from Mount Saint Joseph Academy and Pew Foundation.


In Reply to: Even The Chief is tempted...
Posted by Joe Johnson on 1/12/2001 9:15 AM EST:



I had hopes until Team Update 3. Could they be convinced to reconsider?


: Do you think FIRST will allow teams to use more valves? This would be a great change that would make the pneumatics even more useful.

: Joe J.

[archiver]

Posted by EddieMcD at 03/09/2001 6:36 PM EST


Student on team #121, Islanders, from Middletown High School and NUWC.


In Reply to: Re: What are you going to play?
Posted by mike oleary on 03/09/2001 4:19 PM EST:



/me sticks toung out at mike.

How about The Robots?

-Ed "I wanna be a robot" McDonnell

[archiver]

Posted by Mike at 1/13/2001 11:10 PM EST


Other from Grandview Heights High School.


In Reply to: Re: Even The Chief is tempted...
Posted by Gary Bonner on 1/12/2001 11:56 AM EST:



It seems to me that you can swap motors with another team for their kit. Technically I think that might be open. The update limits you to 6 cylinder and ONLY the parts in the kit. SO, swap parts or design ideas for valves. It does not say you can't have more kits. You are supplied with one but unused kits from other teams are resources.

[archiver]

Posted by Justin Stiltner at 1/14/2001 12:05 AM EST


Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.


In Reply to: More valves
Posted by Mike on 1/13/2001 11:10 PM EST:



: It seems to me that you can swap motors with another team for their kit. Technically I think that might be open. The update limits you to 6 cylinder and ONLY the parts in the kit. SO, swap parts or design ideas for valves. It does not say you can't have more kits. You are supplied with one but unused kits from other teams are resources.


Nope, wont work
if you recived 3 valves in the kit then 3 is all you get to have on the bot at any 1 time, that doesent mean that you can only have 3 in your possesion it just means that at any time there can be only 1 double and 2 single valves on the bot. Same for the other stuff.

Justin Stiltner
Team #388
Epsilon
Grundy Va,

[archiver]

Posted by Eric Reed at 1/12/2001 1:55 PM EST


Coach on team #481, NASA Ames / De Anza High School, from De Anza High School and It could be you!.


In Reply to: Use the pilot operated check valve
Posted by Gary Bonner on 1/12/2001 12:43 AM EST:



I'm guessing it's pretty late to be expecting such a dramatic materials change.

Eric
Team 481

[archiver]

Posted by Elliot Johnson at 1/12/2001 12:45 AM EST


Student on team #218, HP Robotics Team, from Highland Park High School and Double-E Inc..


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



: Ok here is our problem. We need to know how we can get our pneumatics to be able to stop without fully extending or vise versa. In other words how do we control the length of the cylinder by holding down either the trigger or the thumb. As we have it now we press the button once and it extends all the way or contracts all the way. Any help would be appreciated.

There are at least two different ways I know of to slow the cylinders
down to a controllable speed.
The first (easiest & most reliable) is to put one of the little pressure
valves inline with the cylinder's feed. I'm not sure the exact name for
them, they look like little 90 degree elbows and have a screw coming
out of them, like a small water faucet. You adjust the screw until the
cylinder moves at a comfortable speed. To move it to a certain
position, just turn on the pressure switch for the cylinder until it is
where you want it and turn off the switch. The air pressure will remain
in the cylinder so it will maintain it's position. You can also use two
valves, one for each entry into the cylinder, to have different speeds
in different directions.

The other way I've read about it to use a model like PWM for
controlling motors. The solenoid valve is quickly pulsed on and off
rapidly. The pulses begin at a constant frequency (the solenoid is
turned on every x milliseconds) but the length of the pulse depends on
how fast you want the cylinder to move. The length of the pulse can
be between 0 (not moving at all) and the full period (full power).
Anywhere in between should give a proportional speed. This setup is
more complicated, but the speed isn't fixed like with the pressure
regulators. For a better description of PWM, check out this article in
the SRS newsletter:
http://www.seattlerobotics.org//enco...68hc12pwm.html

Hope that helps!
Elliot Johnson
Team 218
Double-E Inc & Highland Park High School Robotics

[archiver]

Posted by Joe Johnson at 1/12/2001 10:21 AM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Re: Controling Pneumatics
Posted by Elliot Johnson on 1/12/2001 12:45 AM EST:



I would be very scared of PWMing the solenoid as a means of providing variable stroke on your cylinder.

The life of the relay contacts is limited. If you try this, be prepared to replace Spikes at more or less regular intervals!

Just my opinion. I have been wrong before.

Joe J.

[archiver]

Posted by Mike at 1/13/2001 11:14 PM EST


Other from Grandview Heights High School.


In Reply to: Controling Pneumatics
Posted by Corvallis on 1/11/2001 7:57 PM EST:



Depending on your design you can use two cylinders back to back (or rod to rod) and your spec lengths will give you a 3 postion cylinder. If you need other ideas use the distributor locator index at www.fpda.org and your password from your pnuematic kit to find someone close to you.

[archiver]

Posted by Jim Meyer at 1/16/2001 8:35 AM EST


Engineer on team #67, HOT Team, from Huron Valley Schools and GM Milford Proving Ground.


In Reply to: Re: Controling Pneumatics
Posted by Mike on 1/13/2001 11:14 PM EST:



: Depending on your design you can use two cylinders back to back (or rod to rod) and your spec lengths will give you a 3 postion cylinder. If you need other ideas use the distributor locator index at www.fpda.org and your password from your pnuematic kit to find someone close to you.

Great Idea! Thanks! If you used different length cylinders you could have 4 positions!