RELAY CONTROL SYSTEMS
Applications of Relay Control Systems in
Electropneumatics:
The entire signal processing needs of an electropneumatic control
system can be implemented with relays. Relay control systems used to
be made in large numbers. Many of these control systems are still in use
in industry today. Nowadays programmable logic controllers are
commonly used for signal processing instead of relay control systems.
Relays are still used in modern control systems however, for example in
an EMERGENCY STOP switching device. The principal advantages of
relay control systems are the clarity of their design and the ease of
understanding their mode of operation.
,Direct and Indirect Control
, Direct and Indirect Control
The piston rod of a single-acting cylinder is to be extended when
pushbutton S1 is pressed and retracted when the pushbutton is
released. Fig. 6.1a shows the associated pneumatic circuit diagram.
Direct control of a single-acting cylinder:
The electrical circuit diagram for direct control of a single-acting
cylinder is shown in Fig. 6.1b. When the pushbutton is pressed ,
current flows through the solenoid coil 1Y1 of the 3/2-way valve. The
solenoid is energized , the valve switches to the actuated position and
the piston rod advances. Releasing the pushbutton results in
interruption of the flow of current. The solenoid is de-energized, the
directional control valve switches to the normal position and the piston
rod is retracted
Applications of Relay Control Systems in
Electropneumatics:
The entire signal processing needs of an electropneumatic control
system can be implemented with relays. Relay control systems used to
be made in large numbers. Many of these control systems are still in use
in industry today. Nowadays programmable logic controllers are
commonly used for signal processing instead of relay control systems.
Relays are still used in modern control systems however, for example in
an EMERGENCY STOP switching device. The principal advantages of
relay control systems are the clarity of their design and the ease of
understanding their mode of operation.
,Direct and Indirect Control
, Direct and Indirect Control
The piston rod of a single-acting cylinder is to be extended when
pushbutton S1 is pressed and retracted when the pushbutton is
released. Fig. 6.1a shows the associated pneumatic circuit diagram.
Direct control of a single-acting cylinder:
The electrical circuit diagram for direct control of a single-acting
cylinder is shown in Fig. 6.1b. When the pushbutton is pressed ,
current flows through the solenoid coil 1Y1 of the 3/2-way valve. The
solenoid is energized , the valve switches to the actuated position and
the piston rod advances. Releasing the pushbutton results in
interruption of the flow of current. The solenoid is de-energized, the
directional control valve switches to the normal position and the piston
rod is retracted
