Electronic Components and Symbols in Control Systems
This section details common electronic components used in control systems, along with their standard circuit symbols. Understanding these symbols is crucial for interpreting circuit diagrams and troubleshooting.
Resistors
Resistors oppose the flow of electrical current. Their resistance is measured in Ohms (Ω).
Symbol: Suggested diagram: A zig-zag line. Function: Current limiting, voltage division, pull-up/pull-down resistors.Units: Ohms (Ω), kiloohms (kΩ), megaohms (MΩ).
Capacitors
Capacitors store electrical energy in an electric field. Their capacitance is measured in Farads (F).
Symbol: Suggested diagram: Two parallel lines. Function: Filtering, smoothing voltage, energy storage, timing circuits.Units: Farads (F), microfarads (µF), nanofarads (nF), picofarads (pF).
Inductors
Inductors store electrical energy in a magnetic field. Their inductance is measured in Henrys (H).
Symbol: Suggested diagram: A coiled wire. Function: Filtering, energy storage, creating oscillating circuits.Units: Henrys (H), millihenries (mH), microhenries (µH).
Diodes
Diodes allow current to flow in only one direction. They have a positive (anode) and a negative (cathode) terminal.
Symbol: Suggested diagram: A triangle pointing to a vertical line. Types: LED (Light Emitting Diode - emits light), Zener Diode (voltage regulation), Rectifier Diode (converting AC to DC).Function: Rectification, voltage regulation, signal demodulation, switching.
Transistors
Transistors are semiconductor devices used for amplification and switching. They have three terminals: Base (B), Collector (C), and Emitter (E).
Types: Bipolar Junction Transistors (BJTs) (NPN and PNP), Field-Effect Transistors (FETs) (JFET and MOSFET).Symbols:
NPN BJT: Suggested diagram: Three lines connected in series with an arrow on the emitter. PNP BJT: Suggested diagram: Three lines connected in series with an arrow on the emitter pointing outwards. N-channel MOSFET: Suggested diagram: Three lines connected in series with an arrow pointing inwards towards the gate. P-channel MOSFET: Suggested diagram: Three lines connected in series with an arrow pointing outwards away from the gate.
Function: Amplification, switching, signal processing.
Integrated Circuits (ICs)
ICs are complex circuits containing many transistors, diodes, and other components on a single semiconductor chip.
Symbols: Various symbols exist depending on the type of IC (e.g., Operational Amplifier, Microcontroller, Logic Gate).Function: Perform a wide range of functions, including amplification, signal processing, logic operations, and memory storage.
Switches
Switches are used to control the flow of current in a circuit.
Symbol: Suggested diagram: A line with a movable part. Types: SPST (Single Pole Single Throw), SPDT (Single Pole Double Throw), DPST (Double Pole Single Throw), DPDT (Double Pole Double Throw).Function: Turning circuits on and off, selecting different circuits.
Potentiometers
Potentiometers are variable resistors, allowing for adjustable resistance in a circuit.
Symbol: Suggested diagram: A zig-zag line with a movable tap. Function: Volume control, brightness control, setting variable voltage or resistance.
Voltage Sources
Voltage sources provide a constant voltage to the circuit.
Symbol: Suggested diagram: A circle with a plus and minus sign. Types: DC Voltage Source (constant voltage), AC Voltage Source (alternating voltage).
Current Sources
Current sources provide a constant current to the circuit.
Symbol: Suggested diagram: A circle with an arrow indicating current flow.
Logic Gates
Logic gates perform basic Boolean logic operations (AND, OR, NOT, NAND, NOR, XOR).
Gate
Symbol
Boolean Operation
AND
Suggested diagram: A D-shape with inputs on the left and output on the right. Output is HIGH only if all inputs are HIGH.
OR
Suggested diagram: A D-shape with inputs on the left and output on the right. Output is HIGH if at least one input is HIGH.
NOT
Suggested diagram: A triangle with a slash through it. Inverts the input signal (HIGH becomes LOW, LOW becomes HIGH).
NAND
Suggested diagram: An AND gate with a circle on the output. The inverse of an AND gate. Output is LOW only if all inputs are HIGH.
NOR
Suggested diagram: An OR gate with a circle on the output. The inverse of an OR gate. Output is HIGH only if all inputs are LOW.
XOR
Suggested diagram: An OR gate with an additional curved line on the input. Output is HIGH if inputs are different.
Thermocouples
Thermocouples are temperature sensors that generate a voltage proportional to the temperature difference between two dissimilar metals.
Symbol: Suggested diagram: Two intersecting lines with a symbol indicating temperature difference. Function: Temperature measurement.
Strain Gauges
Strain gauges are sensors that change their electrical resistance when subjected to mechanical strain.
Symbol: Suggested diagram: A resistor with wavy lines indicating strain. Function: Measuring force, pressure, and displacement.
Microphones
Microphones convert sound waves into electrical signals.
Symbol: Suggested diagram: A circle with sound waves emanating from it. Types: Dynamic, Condenser, Piezoelectric.
Relays
Relays are electrically operated switches used to control circuits with higher power using a low-power signal.
Symbol: Suggested diagram: A coil with contacts. Function: Switching circuits, isolation.