Sometimes Air >Electricity
A typical pneumatic system consists of the following components:
- Compressor
- Accumulator
- Regulator
- Tubing, Adaptors, Splitters and Manifolds
- Solenoid Valves
- Cylinders
And the following diagram illustrated a high-level oveview of how these might be connected together
graph LR;
Compressor-->Regulator;
Regulator-->Splitter;
Splitter-->Manifold;
Manifold-->Solenoid1[Solenoid];
Manifold-->Solenoid2[Solenoid];
Manifold-->Solenoid3[Solenoid];
Manifold-->Solenoid4[Solenoid];
Solenoid1-->Cylinder1[Cylinder];
Solenoid2-->Cylinder2[Cylinder];
Solenoid3-->Cylinder3[Cylinder];
Solenoid4-->Cylinder4[Cylinder];
Splitter-->Valve;
Valve-->Cylinder;
This is the "power source" of your pneumatic system. Every component will need to be connected to the compressor, and air will flow from it through connected tubing, in much the same way that current flows through an electrical circuit when connected to a battery.
This is an optional component that you can use to store a reservoir of pressurised air from the compressor. It acts in a similar way to a capacitor in an electrical circuit, providing a ready source of compressed air when a prop demands it.
A regulator is an adjustable valve that can be used to limit the pressure in certain sections of the pipe. They are somewhat similar to resistors in an electrical circuit.
Like wires, pneumatic tubing is available in a variety of diameters. Larger diameter pipes carry a greater volume of air, but will drain your reservoir faster. Polyethylene will kink if you squeeze it too hard so you won't be able to route it around tight corners. For that, use a dedicated 90' bend connector. Polyurethane is more expensive but does not kink.
I recommend using push-fit connectors. You need to purchase push-fit connectors that match the diameter of the tubing you're using. I'm using 8mm tubing throughout. The other side of the connector will need to match the thread of the component you're connecting to. This is normally a 1/4", but sometimes 1/8". The compressor itself probably has one of these Euro-style push connectors. Don't use barbed connectors - they simply ping off under high pressure.
These very simply allow one air input (from your compressor) to be directed to multiple outputs
A solenoid valve is an electronically-operated switch, much like a relay in an electronic circuit. There are various sorts (discussed in more detail below), but all allow you to direct flow of air to different sections of pipework
A manifold is a solid block (usually made of machined aluminium) that acts as a splitter, combined with a solenoid valve controlling each output. It is somewhat like a 4-channel relay
Cylinders are the most common sort of pneumatic output, creating linear movement to expand/contract when air pressure is applied at the port(s). They are similar to electronic linear actuators.
Compressors are the "power source" of any pneumatic system. They use an electric motor to draw in air and compress it into a storage tank, increasing its pressure. When the pressure in the tank reaches its set upper limit, the compressor automatically shuts off, but the stored air in the tank remains pressurised, and can be directed through a connected network of tubes to any attached devices. You can attach several devices to a single compressor, using splitters. As the air in the tank is depleted, the compressor turns on again and re-pressurizes back to the target pressure again.
Relevant specifications for compressors:
- Pressure (psi): This is the amount of pressure the compressor can generate. Pressure can be measured in various units: Typical values might be 100psi ≈ 7 bar = 700kPa = 0.7MPa. However, you do not need to run all connected devices at the same pressure - regulators can be added to set different pressures at different parts of the circuit. Most props require a minimum psi to operate, but also a stated maximum that you should not exceed; these values typically lie in the range 20 to 100psi. Setting pressure too high will add stress to the mechanism and reduce lifetime of the prop.
- Volume Flow Rate (cfm / l/min): This is the volume of air that the compressor can deliver in one minute. A typical value might be 120 litres/min ≈ 4 cubic feet/min (cfm). Compressors with a higher flow rate also typically have a larger tank size. A compressor with a larger cfm will be able to supply air to more concurrent props.
- Tank Size (litres / gallons): The larger the air holding tank the less the compressor has to work because there will be more air available at all times. A tank of 20 litres ≈ 5 gallons is suitable for most escape room usage of around five simultaneous props, but it never hurts to get a compressor with a larger tank if possible.
- Power: (W / hp): The power of the motor that compresses the air. Typical values might be 750W ≈ 1hp. A more powerful motor will be able to repressurise the tank more quickly, and keep up with multiple props firing.
You might be tempted to buy the most powerful compressor available, but these are of course more expensive, heavier, more bulky, and also typically noisier! Fortunately, it is generally possible to situate the compressor itself some distance away from the props, and run air through longer tubing to where it is needed. As an example of a good, relatively inexpensive, compact compressor: https://www.amazon.co.uk/Hyundai-Electric-Compressor-Release-Fittings/dp/B07TJQZLSF
You'll need to attach a hose with the correct connector to match the outlet of the compressor. Unfortunately there are many different connector types, some of which are shown below. The most common compressor outlet I've seen (in the UK) use female Euro quick-release coupler, in which case you'll want a hose with a Euro male quick‑release plug, also called Rectus 25/26, or CEJN320:
You can see more types of connectors at https://en.wikipedia.org/wiki/Air-line_fitting.
On the other end of the hose, you'll want to attach another connector that will allow it to be attached to the rest of your pneumatic system. From this point onwards, I highly recommend doing away with any of the connector types above, and instead simply use push-fit connectors, such as this PC8-02:
Screw threads are generally expressed in imperial units (1/8", 1/4", 3/8" etc.), while push-fit connectors and tubing are generally expressed in metric units. The naming convention for pushfit connectors is the letters "PC" followed by the outer diameter of the tube accepted in the push end (e.g. "8" for a tube with 8/5 OD/ID), followed by the thread diameter expressed in 1/8"s of an inch.... it's a baffling mixed system, but it's actually not too had to follow once you get used to it. I typically use PC08-02 connectors, which join an 8mm hose to a 1/4" threaded connector. PC06-01 would join a 6mm hose to a 1/8" thread, PC12-04 would join a 12mm hose to a 1/2" thread, etc.
Here's some other types of push-fit connectors:
You may notice that there is no push-fit connector that converts directly from the Euro quick-release outlet of the compressor. Instead, we convert it to a threaded BSP connector first, and then from that to a push-conenctor:
- Euro male quick‑release fitting with 1/4" BSP female thread
- PCxx-02 1/4" BSP male thread to push-fit (where xx is the diameter of the tubing you're using)
or
- Euro male quick-release fitting with 1/4" BSP male thread
- PCFxx-02 1/4" BSP female thread to push-fit (where xx is the diameter of the tubing you're using)
| Description | Ports | Usage |
|---|---|---|
| 2-port, 2-way | Inlet, Outlet | One-way only, "shut-off" valve. Can expel air only, which can be used for effects (e.g. air cannons), but not useful for cylinders |
| 3-port, 3-way | Inlet, Outlet, Exhaust | Outlet port is normally connected to exhaust, but switches to inlet when activated (similar to an electronic relay switching the C terminal from NC to NO). When connected to exhaust, allows air to escape, but does not actively "pull" cylinder back to initial position, so it needs to be reset under force of gravity, or via a spring |
| 4-port, 4-way | Inlet, Outlet1, Outlet2, Exhaust | Used for "push-pull" operation of dual cylinders. |
| 5-port, 4-way | Inlet, Outlet1, Exhaust1, Outlet2, Exhaust2 | Used for "push-pull" operation of dual cylinders, but with separate exhausts allow for separate rate of extension / contraction |