Basic Actuators

Even though some applications in automation and other technolgies do not require movement( like automatic LED lighting or automatic heaters ), there are still times where  movement is necessary in order for a device/machine to be able execute work or processes. Enumerated in this post are some of the common actuators being used.

Permanent Magnet
DC Motor

1. DC Motors
From the name of the motor itself, this motor runs in direct current. Not only it runs in direct current but the rotation of the motor rotates depending on the polarity of current introduced to the motor.
An example of this is when a positive to negative polarity introduction can make the motor turn clockwise while a negative to positive polarity introduction can make the motor turn counter-clockwise. Also the introduction of same polarities can make the motor not to turn at all.
This is one of the reasons why hobbyist usually use DC motors. It is cheaper and easy to control.

Stepper Motor

2. Stepper Motors
This are brushless electric motors that can divide a full rotation into a large number of precise steps.
Stepper motors are more expensive than DC motors and more difficult to control since it uses more inputs. Although more expensive and more difficult to control, this motors are used in accurate movements of machines/devices without using a feedback mechanism.
Stepper motors are controlled by introducing  a sequence of current to targeted wire inputs. Most stepper motors consists of four input wires and a common wire.

Servo Motor

3. Servo Motors
A servo motor is usually an assembly of  a dc motor, a circuit with a control and feedback device and gears connected to a shaft. It is controlled by codes or signals that controls the position of the shaft (particularly an angular position). The degree turn of the shaft depends on the design of the motor.
The motor usually has 3 wires, namely the positive terminal, negative terminal or ground and the control wire.

Pneumatic Cylinder

4. Pneumatics and Hydraulics
Pneumatics is the use of standard cylinders using compressed air/gasses to relay movement. This devices are usually used in automated industrial factories and also applied in robotics. 
It uses an on and off mechanism of valves incorporated in cylinders controlling the input of compressed air/gasses from compressors.
At present, pnuematic muscles are usually used in robotic arms and legs.
In the other hand, Hydraulics is the use of standard cylinders using fluids to relay movement.