Introduction to Industrial Automation

5.7.4   Electrical Actuation of a Valve

With the adaptation of a solenoid in the mechanical construction of the valve, we can achieve an 

electrical actuation of a pneumatic valve. In Figure 5.14a, a simple three way, two-position valve 

Α

Β

Figure 5.10  The two-state operation of a three-port, two-position directional control valve 

controlling a single-acting cylinder.

Figure 5.11  The two-state operation of a four-port, two-position directional control valve con-

trolling a double-acting cylinder.

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Elements of Electro-Pneumatic Components 

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171

Table 5.2  Classical, Basic Directional Valves

Valve Type

Initial Position

Valve Symbol

2/2 Way

Closed

2/2 Way

Open

3/2 Way

Closed

3/2 Way

Open

3/3 Way

Closed

4/2 Way

1 Air Line

1 Exhaust Line

4/3 Way

Middle Position Closed

4/3 Way

2 Exhaust Lines

5/2 Way

2 Exhaust Ports

6/3 Way

3 Air Lines

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172

 

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  Introduction to Industrial Automation

is indicated, that carries a solenoid and a corresponding plunger. The application of electrical volt-

age on the solenoid creates a magnetic field that attracts the plunger inside the valve toward the 

upper position, thus blocking the flow of the pressurized air toward the exhaust point. The pres-

surized air is applied in the air inlet and is directed toward the only potential exit to the cylinder, 

since the electromagnetic field of the solenoid is still keeping the plunger in the upper position 

inside the valve. Thus, if in the air exit a single-acting cylinder has been connected, this opera-

tion would cause the extension of the cylinder’s rod. If the voltage of the solenoid is interrupted, 

the plunger returns to its initial bottom position due to the return spring and thus blocks the 

flow of the pressurized air toward the exhaust and exit points. In this situation, the pressurized 

air exists in the chamber of the single-acting cylinder, and can find an exit (relief) through the 

exhaust point, which means that the single-acting cylinder will return to its normal position. As 

an overview of the described operation, the application of a voltage on the valve’s solenoid moves 

Button

Lever

Pedal

Manual

generally

Switch

(a)

(b)

Figure 5.12  Symbols of various actuation mechanisms for manual control of a direction