Lesson 2 Reading the Diagram — Pneumatics

Pneumatics

In this lesson

I can say what a 3/2 valve does when it is pressed and let go.
I can draw a circuit with symbols.
I can build a circuit from a bench card.

Booklet and slides

Lesson 2 is on pages 4 to 6. Your tasks are there.

Booklet 6A (PDF)

Lesson 2 slides:

Notes and Questions With Answers

Concept 1

Boxes and ports

Key words

Box: one state of the valve.
Port: a hole where a pipe joins the valve.
3/2: 3 ports and 2 states.

A valve symbol is drawn as boxes. Each box is one state of the valve. This valve has 2 boxes: pressed and at rest.

The ports join the bottom box, the one at rest.

Port	What it does
1	Air in, from the air supply.
2	Air out, to the cylinder.
3	Exhaust: used air leaves here.

3 ports and 2 states: we call it a 3/2 valve.

The 3/2 push-button valve symbol. The top box is labelled Box: pressed. The bottom box is labelled Box: at rest. Port 1 joins the air in, port 3 joins the exhaust, and port 2 goes to the cylinder. — Two boxes, three ports.

The real valve has the same three ports. Its symbol is printed on the plate, so you can always check which port is which.

Practice 1

1. State how many states a 3/2 valve has.

Answer

2. One box for each state: pressed and at rest.

2. State which port the used air leaves from.

Answer

Port 3, the exhaust.

You can now…

say what a box in a valve symbol means.
name ports 1, 2 and 3.

Concept 2

Inside the boxes

Key words

Arrow: the path the air takes.
T: that port is blocked.
Spring: pushes the valve back.

Part	What it means
Arrow	The path the air takes.
T	That port is blocked.
Button	Push it to change state.
Spring	Pushes the valve back.

Read the box that sits on the ports. At rest, the T sits on port 1, so the air supply is blocked. The arrow joins port 2 to port 3, so air can leave the cylinder.

The 3/2 push-button valve symbol with four labels: Button on top, Arrow in the top box, T: blocked in the top box, and Spring at the bottom. The exhaust is on port 3. — Button, arrow, T and spring.

Practice 2

1. State what a T in a box means.

Answer

That port is blocked.

2. State what pushes the valve back when you let go.

Answer

The spring.

You can now…

read the arrow and the T in a box.
say what the button and the spring do.

Concept 3

Same valve, different push

Same boxes, same ports. Only the part on top changes: it is what pushes the valve.

Button

A finger pushes it.

Lever

A hand moves it.

Roller

A train presses it as it goes past.

Practice 3

1. Name the valve a hand moves.

Answer

A 3/2 lever valve.

2. State what is the same on all three symbols.

Answer

The boxes and the ports. Only the part on top changes.

You can now…

tell a button, a lever and a roller valve apart.

Concept 4

Draw it full size

Key words

Sliding rule: the long rule across the board. Its top edge draws horizontal lines.
Set square: a triangle that sits on the rule to draw vertical lines and angles.

What to collect

Drawing board
Plain A3 paper
45° set square
60/30 set square
Sharp pencil
Eraser

The drawing board with its parts labelled: scale, 45° set square, 60/30 set square, paper (A3), sliding rule, STOP / GO lock, clamps and drawing board. — The drawing board and its tools.

Using the board

Draw the valve

Draw the rest

Every size

Sizes in mm. Small parts by eye. Pipes across or up only.

The lever valve drawn with its sizes: boxes 30 mm square, ports 15 mm, port 1 8 mm from the box line, port 3 25 mm below, the lever at 45° with 10 mm and 5 mm lengths, the diagonal at 30° and the spring at 30°. — The valve and its sizes.

The whole gate circuit with its layout sizes: cylinder 80 by 20 mm with the rod 25 mm out, the spring at 60°, the cylinder 15 mm and 25 mm above the valve, the pipe 10 mm across then up, and the air in 26 mm left of the valve. The valve is grey. — The whole circuit and its layout sizes.

Check your drawing

Sizes	the same as the guide
Ports	numbered 1, 2, 3
Exhaust	on port 3
Pipes	across or up only

The finished gate circuit drawing: air in and exhaust on the left, the 3/2 lever valve with ports 1, 2 and 3, and a pipe from port 2 across and up to the single-acting cylinder. — The finished drawing.

Practice 4

1. State which edge draws a horizontal line.

Answer

The top edge of the rule.

2. State the size of each box of the valve.

Answer

A 30 mm square. Draw two, one on top of the other.

You can now…

draw horizontal and vertical lines with the board.
draw the gate circuit full size, with symbols.

Air on

Press and let go

The lever gate you build. Tap the picture, or the button beside it, to move the air one step. Orange is air.

Practice 5

Spot the mistake. A pupil wrote: “When I let go, air goes into port 3 and pushes the rod back in.” Find the mistake. Fix it.

Answer

Air goes out of port 3. Port 1 is blocked. The spring pushes the rod in.

You can now…

say what a 3/2 valve does when it is pressed.
say what it does when it is let go.

The build

The lever gate

The job

When the lever is pushed, the rod moves out.
When the lever is let go, the rod moves back in.
The drawing shows every symbol and port.

What to collect

Builder and Safety: one set per team.

Bench card 2
Manifold (air supply)
3/2 lever valve
Single-acting cylinder
Tubing
Goggles, one each

The lever gate circuit: air in on port 1 of a 3/2 lever valve, exhaust on port 3, and port 2 piped to a single-acting cylinder. — The lever gate circuit.

1. Simulate it

Tester and Recorder: start on the computer. Add the parts from bench card 2, join them up and press simulate. Push the lever, then let go.

Open NoPressureSim

The simulation. 1: the 3/2 Valves group is open. 2: the Lever card. An arrow drags it to 3: the lever valve, below the manifold on the left. — Add the lever valve.

Both pipes done. 1: port 1, with the red pipe from the manifold. 2: port 2. 3: the cylinder's port, joined to port 2 by a blue pipe. — Pipe port 1 to the manifold, port 2 to the cylinder.

The simulation running. 1: the lever, pushed. 2: the rod is out. Air has gone through the valve and the blue pipe into the cylinder. — Push the lever: the rod moves out.

The simulation after letting go of the lever: the rod is back in. — Let go: the rod moves back in.

STOP. Air Permit before any air.

Works in the simulation.
Tubing checked.
Regulator at 0.
Goggles on.

Regulator at 0 to build. 1 to 2 bar to test. No permit, no air.

2. Build it: bench card 2

Builder and Safety: parts and bench card 2. Safety reads out each step.

Bench card 2: the baseboard with the manifold along the top (air outlets, gauge and regulator), the lever valve in the middle and the single-acting cylinder below, joined by tubing. — Bench card 2: the lever gate on the baseboard.

3. Test it

Push, let go, listen. Then check each point of the job.

Point	Met?	What did you find?
i Lever pushed: rod out	Yes / No	What pushed the rod out?
ii Lever let go: rod back in	Yes / No	What pulled the rod back?
iii Every symbol and port drawn	Yes / No	Let go: where did the air go?

Check your test

i Yes: air from the valve pushed the rod out.
ii Yes: the cylinder's spring pulled the rod back.
iii Let go: the air went out of the valve's exhaust, port 3.

Regulator back to 0 when you finish.

Challenge

Port Patrol

Each 3/2 valve has one mistake, or none. Find it. Get 4 out of 5 on your first try to earn the Port Patrol badge.

Check

Check your understanding

Pick an answer to see feedback on it. You can then try the others. Your score counts first tries only.

Fill the gaps

Push the button: both boxes slide . Port is now blocked. Let go: the pushes the boxes back. The used air leaves through the .

RAG self-check

Tap Red, Amber or Green for how sure you feel.

Booklet answers: Lesson 2

Try the task in your booklet first. Then tap to check.

Task 1: Now you, then your turn

Question 1, line 2: The air goes into the cylinder and pushes the piston.
Question 1, line 3: The rod moves out. The cylinder extends.
Question 2: Roller pressed: the rod moves out (1). Train gone: the valve springs back and the rod goes in (1).

Task 2: Draw the gate circuit

Ports numbered 1, 2, 3. Ruler used. Exhaust on port 3.

The finished gate circuit drawing with a 3/2 lever valve: air in on port 1, exhaust on port 3, and port 2 piped to the single-acting cylinder.

Task 3: Simulate

Push the lever: the rod moves out. Let go: the rod moves back in.

Task 4: Air Permit and kit

Your Air Permit is signed by Safety and your teacher. The kit works the same way as the simulation. Regulator back to 0.

Task 5: Questions

Question 3: It has 3 ports and 2 states (1).
Question 4: 0 bar (1).

Task 6: Key words

ports, states · 1, 2 · exhaust

Picture glossary

Tap a part to see its symbol, the kit and its poster.

3/2 push-button valve

3 ports, 2 states. A finger pushes it.

3/2 lever valve

The same valve. A hand moves the lever.

3/2 roller valve

The same valve. Something moving presses the roller.

Single-acting cylinder

Air pushes the rod out. A spring pushes it back in.

Air supply

Where the air comes in. It joins port 1.

Exhaust

Where used air leaves. It is on port 3.

Next: Lesson 3 · Control the flow Coming soon

Sources & credits: the gate circuit and bench card 2 are adapted from the Matrix CP2080 Pneumatics Essentials Worksheet 1 (© Matrix Technology Solutions Limited). Kit drawings by R Stewart, from the Matrix CP2080 kit. Drawing board pictures drawn by R Stewart from photos of the class boards. Simulator screenshots: NoPressureSim by Peter Strain (NoStrainSims), free and open to all. Text, symbols, drawings and challenge by R Stewart. R Stewart - October 2026