When building a robot for competition, you must consider the challenge, your strategy, and your
means of accomplishing the challenge. The goal of this is to get your team more familiarized
with pneumatics, the use of pressurized air to operate your robot.
Pneumatics are often used as a quick and light way to extend or retract robot parts. During
LOGOMOTION, many teams used pneumatics to extend their robot's arm, so they could score
tubes on the upper rack, and they could retract that same arm in order to keep the robot balanced
Download: Pneumatics Basics
The air compressor is the component that actually compresses the air
for use in the pneumatic system. The air compressor in the 2011 KOP
was light enough to be mounted on the robot, ensuring the pneumatic
system will never run out of air. To power the compressor, it needs to
be wired to a relay with a 20A breaker on it. While powered, the
compressor will vibrate (a lot), so be sure to mount it on something
solid. When programming, remember that a relay has four modes:
On, Off, Forward, and Reverse. Only program the relay Forward, so
the compressor will compress air and add it to the system. If you
program the relay Reverse, the compressor will suck air out of the system.
THAT IS VERY BAD.
Pressure Relief Valve
The pressure relief valve is the component of the pneumatic system that
makes sure the total PSI (Pounds per Square Inch) of the system does not
exceed 120 PSI. The pressure relief valve should be connected right to the
compressor, as seen in the compressor photo above.
This sensor detects the pressure of the pneumatic system. If the pressure is too
low, the pressure switch sends a signal to the digital sidecar and starts the relay
that is connected to the compressor. When the pressure gets to 115 PSI, the
switch sends a signal to the relay and stops it, saving battery. This ensures the
PSI of the system is never too high or too low.
Air Tank (Accumulator)
The air tank is what actually stores the air for the
pneumatic system. With one tank, you can maintain
120 PSI, but you will run out faster than if you had two
tanks. Also note that the air tank that is provided in the
KOP is not the only air tank available. The tank included in the 2011 KOP is 32 in.3.
This is the main regulator, which is somewhat similar to the pressure relief
valve. The pressure relief valve ensures that the total pressure of the system
does not exceed 120 PSI. The main regulator, however, makes sure that the
total pressure going to the cylinders is no greater than 60 PSI. The total force of
a cylinder is equal to the area of a cylinder times the total pressure. Say you
have a cylinder with an area 5 in.2, but you don't have a regulator, so the
cylinder is fired at 120 PSI. The total force the cylinder is firing at is 600
pounds. However, with a regulator, the total force is only 300 pounds. This
makes the cylinder less dangerous, yet still lets the robot operate with enough force to run well.
You can also modify the regulator to lower the total pressure going the cylinders even more.
A solenoid is a lot like a relay, only for a pneumatic system. Electrically, a
solenoid has two sides, and each side can be plugged into the solenoid
breakout, one of the cRIO modules. Just like a relay, a solenoid can control
the flow of air in four ways: On, Off, Forward, and Reverse. Each solenoid
has a small button on them that manually opens the valves. In the rookie
KOP, teams were given a 24V solenoid. To operate these, the solenoid
breakout needs to be powered by the 24V power slot on the power distribution board (the same
slot that also powers the cRIO).
The plug valve is a safety measure for the pneumatic system. When the robot
is not in use, it is a good idea to open the valve and release the pressure. That
way, there is no pressure in the system to activate any cylinders
This is the tubing used to connect each pneumatic component in a circuit.
The pneumatic tubing used on your robot should be rated to 125 PSI. When
cutting the tubing, make sure to cut at a level horizontal. Otherwise, the
tubing will not securely fit into the plugs and the pneumatic system will leak.
Cylinders are the component of the pneumatic system. They can either be
retracted or extended. Cylinders can be custom ordered from Bimba.
They come in ¾" diameter, 1 1/16" diameter, 1 ½" diameter, and 2"
Two pressure gages are required in the system. One gage should be located on
the accumulator side of the regulator, the other on the solenoid side (or in the
regulator pressure port). The regulator should be between them. The
accumulator pressure should be less than 125 psi. The working pressure should
not exceed 60 psi.
When screwing together fittings for the air system, always put a wrap of
Teflon tape on the threads to insure an air-tight seal.
Simple Pneumatic Circuit