Getting Started with Pneumatics with the V5 System

Pneumatics are a very efficient way of creating linear motion. Pneumatic cylinders are very effective for activating claws, shifting gears between gear systems, and many other applications. In addition, pneumatics add another energy source to your robot, are very fun to work with, and will provide knowledge of pneumatic systems which are widely used in industry.

When pneumatic cylinders are activated they are either fully extended or fully retracted.

This article will explain:

Note: VEX Robotics Competition (VRC/VEX U/VEX AI) teams who are planning on using pneumatics need to carefully read the Robot Rules regarding pneumatic systems in the Game Manual.


How Pneumatics Work

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Pneumatics work by using air pressure. This can be created with something as simple as a bicycle tire pump.

The basic pneumatic system uses a storage tank in which the air pressure can be pumped up with the bike pump, pneumatic tubing to connect the devices, a valve to control the release of pressure, and a pneumatic cylinder.

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A double acting pneumatic cylinder works when a valve releases air pressure into the bottom of the cylinder. The air pressure pushes on the surface area of an internal piston which forces the piston and piston rod out of the cylinder.

As the piston/piston rod moves out, exhaust air flows out the top of the cylinder

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The valve can also be set to release air pressure into the top of the cylinder. When this happens the air pressure pushes the piston and piston rod back into the cylinder.

As the piston/piston rod moves in, exhaust air flows out the bottom of the cylinder.

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A single acting pneumatic cylinder works mostly in the same way, with the exception that a spring pushes the piston/piston rod back in. A single acting cylinder only has one port/fitting for the air to go in and the air to go out.

For more information about the available pneumatic kits for the V5 system, view the Selecting a Pneumatics Kit for the V5 System article from the Knowledge Base.


Pneumatics Components

Air Storage

Air storage, for both the double acting cylinders and the single acting cylinders, essentially use the same components.

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Air Reservoir - Reservoir, 1-1/2" X 4", w 1/8"NPT & M5 port - US14227-S0400

The Air Reservoir is where the air is stored for the pneumatic system.

Note: End nuts can be removed from the reservoir to reduce weight.

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The reservoir has two ports. One on each end. These threaded ports will accept the Schrader tire pump valve or the reservoir fitting.

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The reservoir can be attached to the robot by wrapping 11” Zip Ties around the reservoir and a structural piece.

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The reservoir can also be attached to the robot by wrapping a Steel Bar around the reservoir and placing a screw through the holes where the two sides of the bar meet. A nut can be placed on the screw forming a clamp.

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Tire Pump Fitting (Schrader tire pump valve) is where an air pump is attached/detached to pressurize the pneumatic system.

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A single layer of Teflon tape can be wrapped around the threads of the fitting prior to screwing it into the port of the Air Reservoir. This will help make an airtight seal.

For more information on creating airtight seals refer to the Preventing Air Leakage in a VEX Pneumatic System article from the Knowledge Base.

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The core of the Schrader tire pump valve can be pushed in to release the pressure from the system.

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The Fitting for Reservoir is where the pneumatic tubing is inserted which will feed the air pressure to the rest in the system.

The fitting’s threads comes with teflon already applied to reduce air leaks

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All of the pneumatic tubing fittings accept the tubing by simply inserting the tubing into the fitting until it comes to a stop.

To release the tubing the outer collar needs to be pushed in towards the fitting and then the tubing can be removed.

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"T" Fitting - "T" Fitting for Valves. This “T” Fitting will allow the air feed to be split in order to feed two valves.

Note: the fitting can also be used to control two single acting cylinders with the one value.

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The Pressure Regulator - Mini Regulator w/ 4mm Fittings can adjust the air pressure flowing downstream in the system.

The pressure is adjusted by turning the stem, moving it in or moving it out.

With the stem turned all the way out the air pressure will be the highest. The amount of air pressure determines the amount of force the cylinder will apply.

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The double acting pneumatics kit comes with a On/Off Switch - Finger Valve.

This will allow you to turn the air on for the system and release the air pressure from the system.

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Ensure the arrows embossed on the valve are pointing away from the Air Reservoir and towards the system. In other words the arrow should be pointed in the direction the air will be traveling.

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When the knob is in line with the tubing the air is on in the system.

When the knob is aligned perpetually across with the tubing the air is turned off and it releases the air pressure from upstream in the system.

Air Control

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Double Acting Air Control

The Solenoid, Fwd, Reverse - 5/2 Single Solenoid Valve controls the airflow for the double acting cylinders.

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Fittings for Valves, these screw into the ports on the solenoid valve.

Take care not to cross thread the fittings as they are being screwed into the port.

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Screw a fitting into both Port A and Port B on the top of the valve.

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Screw a fitting into the port labeled P where the air pressure will be fed into the valve.

Leave the two ports labeled R open to allow the exhaust air to be released.

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In the default setup, Port A will feed the bottom port of the double acting cylinder and Port B will feed the top port. This will have the cylinder start with the rod retracted.

However, if there is a condition where it is advantageous to start with the cylinder’s rod extended the two ports can be switched.

The solenoid valves can be attached to the robot using zip ties. Note: do not cover the exhaust ports of the solenoid with the zip ties. If this occurs, the cylinder will not move.

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There is a small blue button on the top of the valve which can be depressed using a small tool like a Star Drive Key or pen. Pressing this button will manually open the value in order to test the airflow to the cylinder.

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The Solenoid Driver - Cable w/Drive, plugs into the double acting solenoid valve on one end and provides a connection to the 3-Wire port on the V5 Robot Brain on the other end.

An Extension Cable can be used between the Solenoid Driver and the V5 Robot Brain if more length is necessary.

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Single Acting Air Control

Solenoid, On/Off - 3/2 Solenoid Valve controls the single acting cylinders.

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The same type of Fittings for Valves screw into the ports on the solenoid valve.

Again, take care not to cross thread the fittings as they are being screwed into the port.

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Screw a fitting into Port A on the top of the valve.

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Screw a fitting into the port labeled P where the air pressure will be fed into the valve. Leave the port labeled R open to allow the exhaust air to be released.

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Port A will feed the bottom port of the single acting cylinder.

Solenoid valves can be attached to the robot using zip ties.

Note: Do not cover the exhaust port of the solenoid with the zip ties. If this occurs, the cylinder will not move.

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There is a small orange button on the top of the valve which can be depressed using a small tool like a Star Drive Key or pen. Pressing this button will manually open the value in order to test the airflow to the cylinder.

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The Solenoid Driver - Cable w/Drive, plugs into the single acting solenoid valve on one end and provides a connection to the 3-Wire port on the V5 Robot Brain on the other end.

An Extension Cable can be used between the Solenoid Driver and the V5 Robot Brain if more length is necessary

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Both the double acting solenoid and the single acting solenoid can be controlled using a digital out device within a custom VEXcode V5 project.

For more information about programming pneumatics, see the Controlling Pneumatics Using Buttons on Your Controller article from the Knowledge Base.

Pneumatic Cylinders

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Double Acting Cylinder

The Cylinder, Bi-directional - Double Acting Cylinder 10mm Bore, has a port on both ends.

The rod is threaded with two nuts. These can be used to attach the Cylinder Rod Pivot.

The front of the cylinder is threaded and can be used as an alternative method to mount the cylinder by drilling a hole in a piece of structure, inserting the cylinder, and then securing with the cylinder nut.

If this method of attachment is not being used the nut can be removed to reduce weight on your robot.

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The Flow Meter - M5 elbow meter out flow control, can be screwed into the top port of the cylinder.

The flow meter can control the airflow through the cylinder which will control the speed the cylinder’s rod will extend and retract.

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The flow meter can be adjusted by turning the inner ring upwards to increase the flow or downwards to decrease the flow. The ring can be turned using a blade screwdriver.

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The Fitting for Cylinders - M5 Male Connector for Cylinders, can be screwed into the bottom port of the cylinder.

As with all of the fittings, care needs to be taken not to cross thread the fitting as it is being screwed in.

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The Cylinder Rod Pivot can be attached to the cylinder rod by placing it between the two nuts on the threaded portion of the rod.

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The Cylinder Mount can be attached to the cylinder using a 1 inch #8-32 VEX screw and a nylock nut.

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The Cylinder Mount can be mounted to a piece of structure on the robot. The Cylinder Rod Pivot can be attached to the component which it will be moved using a screw or a shaft.

Note: do not mount the cylinder such that there is a side force being applied to the rod of the cylinder. If the rod of the cylinder becomes bent, the cylinder will not function.

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Single Acting Cylinder

The Cylinder - Single Acting Spring Return Cylinder 10mm Bore has a port on its end.

The rod is threaded with two nuts. These can be used to attach the Cylinder Rod Pivot.

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The Fitting for Cylinders - M5 Male Connector for Cylinders, can be screwed into the bottom port of the cylinder.

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The Cylinder Rod Pivot and the Cylinder Mount can be attached to the single acting cylinder in the same manner as they are for the double acting cylinder described above.

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The Cylinder Mount can be mounted to a piece of structure on the robot. The Cylinder Rod Pivot can be attached to the component which it will be moved using a screw or a shaft.

Note: Do not mount the cylinder such that there is a side force being applied to the rod of the cylinder. If the rod of the cylinder becomes bent, the cylinder will not function.

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Pneumatic tubing is used to connect all of the devices together.

It can be cut to length using a pair of sharp utility scissors.


Two Sample Layouts for Pneumatics

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A sample layout for the double acting cylinder:

  1. Air will be pumped from a bike pump into the Schrader valve of the Air Reservoir.
  2. The pressurized air flows out the fitting on the other end of the reservoir and into the On-Off Switch.
  3. From the switch the pressurized air will feed the Pressure Regulator.
  4. From the Pressure Regulator the air will flow into the Double Acting Solenoid Valve.
  5. Depending on the state of the solenoid valve, the air will either flow out of Port B and into the top of the cylinder or air will flow out of Port A and into the bottom of the cylinder extending its rod.
  6. The solenoid valve will be controlled by the Solenoid Driver Cable attached to the 3-wire port of the V5 Robot Brain

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A sample layout for the single acting cylinder:

  1. Air will be pumped from a bike pump into the Schrader valve of the Air Reservoir.
  2. The pressurized air flows out the fitting on the other end of the reservoir and into the Pressure Regulator.
  3. From the Pressure Regulator the air will flow into the Single Acting Solenoid Valve.
  4. Depending on the state of the solenoid valve, the air will either exhaust out of Port A or air will flow out of Port A and into the bottom of the cylinder extending its rod.
  5. The solenoid valve will be controlled by the solenoid driver cable attached to the 3-wire port of the V5 Robot Brain

Calculating Force of Cylinders

The equation for calculating the Output Force for a specific pressure is given as: 

(Cross Sectional Area of Cylinder) x (Internal Air Pressure) = Force 

The cylinders bore of the VEX Pneumatic Cylinders is 0.39 in (10 mm). From this we can calculate the cross sectional area of the cylinder by using the equation for the area of a circle: 

(Diameter / 2)² x π = Area

As we are given the cylinder bore (inside diameter) and we know that Pi ≈ 3.14, we can calculate the area to be:

 (0.39 in / 2)² x 3.14 = 0.12 in² 

We can now plug this number into our original equation and calculate the cylinder output force:

0.12 in² x 100 psi = 12 Pounds of Force (at 100 psi)


For safety guidelines when working with pneumatics, refer to Precautions and Safety Guidelines When Working with VEX V5 Robots.