Pradeep Singh | 1st Feb 2017
Actuators convert an electrical signal into a corresponding physical quantity such as movement, force, sound etc. An actuator is also classed as a transducer because it changes one type of physical quantity into another and is usually activated or operated by a low voltage command signal. Actuators can be classed as either binary or continuous devices based upon the number of stable states their output has.
For example, a relay is a binary actuator as it has two stable states, either energized and latched or de-energised and unlatched, while a motor is a continuous actuator because it can rotate through a full 360o motion.
Let’s explore some of the basic actuators you may use in your IoT projects –
1. Servo Motors:
A Servo is a small device that incorporates a two wire DC motor, a gear train, a potentiometer, an integrated circuit, and a shaft (output spine). The shaft can be positioned to specific angular positions by sending the servo a coded signal. Of the three wires that stick out from the servo casing, one is for power, one is for ground, and one is a control input line.
When a control signal is applied to a Servo that represents a desired output position of the servo shaft, it (servo) applies power to its DC motor until its shaft turns to that position. It uses the position-sensing device to determine the rotational position of the shaft, so it knows which way the motor must turn to move the shaft to the commanded position.
2. Stepper Motors:
Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called “phases”. By energizing each phase in sequence, the motor will rotate, one step at a time. With a computer controlled stepping, you can achieve very precise positioning and/or speed control.
A servomotor consumes power as it rotates to the commanded position but then the servomotor rests. Stepper motors continue to consume power to lock in and hold the commanded position.
3. DC Motors (Continuous Rotation Motors):
Direct Current (DC) motor is the most common actuator used in electronics projects. They are simple, cheap, and easy to use. Also, they come in a great variety of sizes, to accommodate different tasks. DC motors convert electrical into mechanical energy. They consist of permanent magnets and loops of wire inside. When current is applied, the wire loops generate a magnetic field, which reacts against the outside field of the static magnets.
4. Linear actuator:
A linear actuator is an actuator that creates motion in a straight line, in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required.
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. The advantage of relays is that it takes a relatively small amount of power to operate the relay coil, but the relay itself can be used to control motors, heaters, lamps or AC circuits which themselves can draw a lot more electrical power.
A solenoid is simply a specially designed electromagnet. Solenoids are inexpensive, and their use is primarily limited to on-off applications such as latching, locking, and triggering. They are frequently used in home appliances (e.g. washing machine valves), office equipment (e.g. copy machines), automobiles (e.g. door latches and the starter solenoid), pinball machines (e.g., plungers and bumpers), and factory automation.