1. Electrical actuation systems

2. Intro.. Actuator is a device which is used to actuate a process.
Actuate is to operate the process.
Switching devices – mechanical switches, eg. relay and solid state switches, eg diodes, thyristors and transistors app – switch on or off electrical devices
Solenoid – type devices used to actuate valves of hydraulic and pneumatic systems. (flow control)
Drive systems – DC motor, AC motor and stepper motor.

3. Basic electronics
Semi-conductor
Diode
Transistor
Resistor

4. Mechanical switches Electronics specification and abbreviation
Expansion of abbreviation
British mains wiring name
Description
Symbol
SPST
Single pole, single throw
One-way
A simple on-off switch: The two terminals are either connected together or disconnected from each other. An example is a light switch.
SPDT
Single pole, double throw
Two-way
A simple changeover switch: C (COM, Common) is connected to L1 or to L2.
SPCO
Single pole, centre off 
switches with a stable off position in the centre
DPST
Double pole, single throw
Double pole
Equivalent to two SPST switches controlled by a single mechanism
DPDT
Double pole, double throw
Equivalent to two SPDT switches controlled by a single mechanism.
DPCO
Double pole changeover or Double pole, centre off
Equivalent to DPDT. Some suppliers use DPCO for switches with a stable off position in the centre
Mechanical switches

5. Mechanical switches
Relay - A relay is an electrically operated switch.

6. Relay
Electrically operated switches in which changing the current in one circuit switches a current on or off in another circuit.
NO – normally open , NC – normally closed
Output from controller is small so it is often used with transistor.
Relays are inductances
Free – wheeling or fly back diode.
Importance
To operate a device which needs larger current.