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 FIRST is more than FRC. - gblake [more] |
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Here's a servo controlled valve I designed for 1015 a few years ago. It was made for isolating a pneumatics subsystem, but it would work well with low pressures or vacuum.
It was made from a kit servo, a chunk of 2" x 3" x 1/8" box from that year's kit (chopped at one end), a hacked down slice of 8020 X-extrusion (tweaked slightly via Dremel for a snug, slip-on fit), a the kit's vent valve, and a pair of kit SMC swivel connectors. NO modification of servo, valve, or connectors occured. The "valve twister" is simply slid onto the knob.
This valve was used by my old team 1015 in Stack Attack, to solve a deployment problem. Our fork-lift couldn't be fully down, NOR up, because either violated "Initial Dimensions". It had to be held at an ANGLE.
That year's rules also said you could ONLY used what was IN the pneumatics kit. We had three cylinders, which already tied up the three supplied valves in basic control. We couldn't buy another to plug the vent, nor substitute a valve (like we can now) for one that simplifies multi-positioning pneumatics design.
Well, that meant we needed ONE more valve than was supplied, just to hold and isolate the forklift deployment cylinder from the system at startup at "half mast". (Hmmm...)
The idea came to me when I noticed the vent valve was 1.75" between ports, which meant it fit *exactly* within the 2" (OD) x 1/8" thick box or U-channel extrusion. I also noticed they didn't REQUIRE the vent valve to BE a vent valve that year (unlike now)...
So, this valve was born...
Construction note: With appropriately placed holes, the valve is retained by the two SMC fittings. There are holes along the long side on the left for mounting the assembly to the robot.
The only problem with THIS particular copy is that it was SLOW to actuate. The kit's vent valve is tough to turn, and is almost at the limit of the servo's capacity. (It took over a second to toggle, but it DID work.) A ball bearing valve, or a stronger servo would be *highly* advised in a newer copy. (...Besides, this year's rules REQUIRES a vent valve to be present, so you'll need a second manual valve anyway to make this.)
Anyway - We built this one and connected it to the vent output of thr forklift deployment valve. We prepositioned the forklift deployment cylinder with slow motion pre-round, then manually shut THIS valve off. THAT held our fork-lift at the appropriate angle to make dimensions.
The program then simply commanded it to ON when the robot was enabled. Instant "transformer" to Operating Configuration! It worked like a charm, every time...
The reason I post this now is that I mentioned in a Pneumatics thread that this "class" of valve is Non-Piloted. THEREFORE, a faster variant of it made with either a stronger servo or a ball bearing manual valve MAY have application to someone here for this year's contest, to control vacuum.
It may also be used like we used it, to shift your robot (in this case via one or more additional cylinders) from your initial dimension configuration to "operating configuration, without requiring you to tie up a valuable kit valve.
Good luck!
- Keith
Discussion
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20-01-2007 23:20
Nate Laverdure
Re: pic: Servo Controlled Valve
Interesting and novel idea, but I can't think of a use for it.
And does this violate <R99> (customizing pneumatics components)?
20-01-2007 23:24
AV_guy007
Re: pic: Servo Controlled Valve
my guess is that it open the value to empty the pneumatics system instead of doing it by hand
20-01-2007 23:26
Nitroxextreme
Re: pic: Servo Controlled Valve
My best guess at an application would have to be some sort of cut off valve to lock in a vacum....seems like a solenoid would also provide the same effect
20-01-2007 23:27
lukevanoort
Re: pic: Servo Controlled Valve
I'd guess it is for controlling vacuum. I'm surprised the servo has enough torque, those valves can be sort of sticky.
20-01-2007 23:29
ADZDEBLICK
Re: pic: Servo Controlled Valve
would this work as a variable solenoid of some sort?
20-01-2007 23:33
redbarron
Re: pic: Servo Controlled Valve
Maybe it dumps the system to let down the ramp instead of using a solenoid to extend or retract a piston if its a one shot deal.
Though i dont think thats legal is it?
20-01-2007 23:59
kmcclary
Re: pic: Servo Controlled Valve
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Originally Posted by Nate Laverdure
Interesting and novel idea, but I can't think of a use for it.
And does this violate <R99> (customizing pneumatics components)? |
Gee... I see that CDF put the pic up before I had a chance to add my comments. (Wow! 99 views already while I typed!) Please look at the text now supplied, for construction and usage notes.
I hoping that this design may be found useful for:
-- a rookie team with limited budget for real control valves,
-- someone wishing a non-piloted valve for vacuum or low pressure cylinder apps (below what kit valves can control),
-- a team that wishes to make a Starting-to-Operating configuration transformer setup, without wasting an expensive kit valve for the purpose,
-- any application where you need to isolate a subsystem (IOW prevent something from working) from start of round until the desired critical moment, or
-- stopping a cylinder in a mid-position, by plugging the vent port.
BTW, if you DO replicate this in some version, PLEASE drop me a note to tell me your mods, and how you used it!
Good luck with your build!- Keith
21-01-2007 00:12
kmcclary
Re: pic: Servo Controlled Valve
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Originally Posted by Nitroxextreme
My best guess at an application would have to be some sort of cut off valve to lock in a vacuum....seems like a solenoid would also provide the same effect
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Nope, you can't use a kit valve for directly controlling vacuum. If you look at the kit valves specs, they are ALL "piloted". That means they need positive air pressure on their inputs (of several TENS of PSI), just to operate. Therefore, they can only control air going INTO your Vacuum Generator, and the VG must be directly connected to your suction cup. (Which DOES work...)
But if you are intending to generate vacuum with a kit motor, be aware that none of the kit valves are capable of directly controlling vacuum, because even a perfect 14.7 PSI differential across them isn't a sufficient pilot pressure to allow them to operate.
- Keith
21-01-2007 01:29
AdamHeard
Re: pic: Servo Controlled Valve
This would be nice to automatically close the valve at the start of the match. We lost 2-3 matches in 2005 from not closing our valve which powered our gripper.
22-01-2007 15:48
Ed Sparks
Re: pic: Servo Controlled Valve
Not to rain on anyone's parade..........
This valve's main purpose is to "Dump" air pressure quickly in the event of some emergency (like the main breaker for your pneumatics). If you have this thing embedded in some other device, you obviously will not be able to access it. It's suppost to be located in a place that can be accessed quickly (again, like the main breaker).
Hint:
I would not pass this thing in tech inspection.
22-01-2007 16:17
jgannon
Re: pic: Servo Controlled Valve
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Originally Posted by Ed Sparks
Not to rain on anyone's parade..........
This valve's main purpose is to "Dump" air pressure quickly in the event of some emergency (like the main breaker for your pneumatics). If you have this thing embedded in some other device, you obviously will not be able to access it. It's suppost to be located in a place that can be accessed quickly (again, like the main breaker). Hint: I would not pass this thing in tech inspection. |
22-01-2007 19:53
Nate Laverdure
Re: pic: Servo Controlled Valve
Will it really work to "lock in" a vacuum seal on the inner tube, or will you have to constantly supply suction to maintain grip?
22-01-2007 21:58
DonRotolo
Re: pic: Servo Controlled Valve
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Originally Posted by kmcclary
stopping a cylinder in a mid-position, by plugging the vent port.
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Originally Posted by Nate Laverdure
Will it really work to "lock in" a vacuum seal on the inner tube, or will you have to constantly supply suction to maintain grip?
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Don
26-01-2007 01:00
Brian C
Re: pic: Servo Controlled Valve
Maybe I'm oversimplifying this but. Why not just run an additional variable regulator downstream between the solenoid valve and the vacuum generator?
This way you can operate the kit valves at an increased pressure (ie: 60psi) and then regulate the pressure down to your desired psi for the vacuum generator.
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