Electrical Components
Machine movements in automated systems utilize a variety of electrical methods and media to provide and assist in power transmission. Typical automated machines use a combination of electrical, electronic and electromechanical technologies to move loads.
These technologies play specific roles in automated machines and are represented by a variety of field devices. Some devices are designed to provide electrical or electromechanical propulsion, while others provide electronic signals. The differences between devices are in the circuitry and internal add-on components.
Electrical equipment
Electrical equipment is designed to deliver power for energy and distribution. These devices convert electric current into light, heat, or motion. A device is considered electrical if it strictly utilizes electricity for energy and power distribution.
You will typically find these devices in machine control cabinets. Alternating current (AC) flows from the building's main power supply into the machine's distribution box. Electrical equipment is designed to control the current that flows into a machine through a circuit. The circuit is a loop that conducts the flow of energy to the load and back again.
The circuit has four basic parts:
- The power supply provides energy to the load and consists of-
- Voltage- It provides the thrust behind the charge. It is the pressure that moves the charge.
- Current- Voltage pushes to produce a current of electrons. Without voltage there is no current.
- Resistance- The conductivity of the substrate affects the resistance. The amount of resistance depends on the size and composition of the substrate.
- Conductors provide the path. Electrical energy is conducted along metal wires such as copper and aluminum.
- Switches control circuits by adding a method of switching between open or closed (hence open or closed).
- A load device is part of the circuit loop. Electricity flows through the device, activating it.
Electronics
The highly consistent relationship between voltage, current, and resistance allows for better control of circuits and can produce more meaningful results.
Ohm's Law states [V (voltage) = I (current) x R (resistance)
We control either of these variables by controlling the other two. This brings us to electronic components.
Electronic components are the tools used to control these variables and thus control the circuit. By adding active and passive electronic components to a typical circuit, we can manipulate electrical currents to produce signals that communicate between electronic machine devices. Depending on the electronic component, signal amplification, computation and data transmission functions can be utilized.
A key component in electronic circuit design:
- Capacitor- A two-terminal element that stores energy in an electric field in an electrostatic manner.
- Resistor- A passive two-terminal element that provides resistance in a circuit. Reduces voltage and current.
- Diode- A two-terminal device that limits current in one direction, such as a check valve. It once consisted primarily of gas vacuum tubes, but is now almost entirely replaced by semiconductors and is considered a solid-state component.
- Transistor- A three-terminal device that performs two functions. It is made of semiconductor material and acts as a switch or amplifier for electronic signals, controlling the flow of voltage and current. It is considered a solid-state component.
- Transducer- A transducer is a device that converts energy from one form to another. An actuator is a form of transducer. Transducers act as sensors because they receive and respond to, and forward, system signals, just as they do when used as thermocouples.
In today's automation, electronic devices contain integrated circuits that form circuit systems for specific tasks. The circuits are dispersed on semiconductor wafer material and encapsulated within a chip. Semiconductor materials are not conductors or insulators. Semiconductors are somewhere in between. This technology is popular because its charge carriers (electrons and holes) are easily manipulated by internal (boron or phosphorus doping) and external (temperature, light, etc.) factors.
Devices that rely exclusively on semiconductor components are considered solid-state. Modern transistors and diodes, integrated circuits, light-emitting diodes (LEDs), and liquid crystal displays (LCDs) are all solid-state components. Two examples of solid-state devices marketed for automation include relays and sensors. These devices were originally and are still sold in electromechanical versions. Solid-state devices provide the same functionality as their electromechanical counterparts, but do not include moving parts.