Electronic components and symbols used in control systems.

Materials and Components

Objective: Electronic Components and Symbols Used in Control Systems

Control systems are like the nervous system of a machine – they sense, decide, and act. To build one, we need a toolbox of electronic components and a symbol language that engineers use to draw circuits. Below you’ll find a quick‑reference guide, colourful examples, and a simple project idea.

1. Key Electronic Components

• 🔌 Power Supply – provides the voltage and current needed. Think of it as the energy source that keeps the machine alive.
• 🔋 Battery – a portable power supply. Like a rechargeable backpack for your circuit.
• 📶 Sensor – detects a physical quantity (temperature, light, position). It’s the eyes of the control system.
• 🧲 Magnet / Hall Effect Sensor – detects magnetic fields. Imagine a compass inside the circuit.
• 🧱 Resistor (R) – limits current. Analogy: a narrow pipe that slows down the flow of water.
• ⚡ Capacitor (C) – stores charge. Analogy: a water tank that can release water when needed.
• 🌀 Inductor (L) – stores magnetic energy. Think of it as a spring that resists changes in current.
• 🛠️ Transistor (BJT / MOSFET) – acts as a switch or amplifier. Like a traffic light that controls the flow of cars (current).
• 📦 Integrated Circuit (IC) – a small chip containing many components. It’s a mini‑factory on a single board.
• 🧩 Diode (D) – allows current to flow in one direction only. Picture a one‑way street.
• 📐 Potentiometer (POT) – variable resistor. Think of a dimmer switch for light.

2. Symbols in Schematics

Schematics use standard symbols so everyone can read the same drawing. Below is a quick reference table.

3. Example: Simple Temperature Control Loop

1. Goal: Keep a small heater at 50 °C using a thermostat.
2. Components:
   • 🔌 5 V DC power supply
   • 🧲 Thermistor (temperature‑dependent resistor)
   • 🛠️ NPN transistor (BJT) as a switch
   • ⚡ 5 W heater element (resistor)
   • 🧱 10 kΩ resistor (bias)
   • 📦 555 Timer IC (for simple oscillator)
3. Basic Principle: The thermistor changes resistance with temperature. When the temperature drops below 50 °C, the transistor turns on, heating the element. When the temperature rises, the transistor turns off.
4. Sketch the schematic:
   • Power supply → 555 Timer → transistor base (via 10 kΩ resistor) → heater.
   • Thermistor connected in a voltage divider with a fixed resistor, feeding the 555 Timer’s threshold input.
5. Math check: If the thermistor’s resistance at 50 °C is $R_{50} = 10\,k\Omega$, and the fixed resistor is $R_f = 10\,k\Omega$, the voltage at the divider is $V_{out} = V_{in}\frac{R_{50}}{R_{50}+R_f} = 5\,V \times \frac{10}{20} = 2.5\,V$. The 555 Timer can be set to trigger when $V_{out} < 2.5\,V$.

4. Summary & Quick Quiz

You’ve learned the main electronic parts and how they’re drawn. Remember:

• Resistors limit current – like a narrow pipe.
• Capacitors store charge – like a water tank.
• Transistors switch or amplify – like a traffic light.
• Symbols are universal – they let anyone read your circuit.

📝 Quiz question: Which component would you use to convert a 12 V battery into a stable 5 V supply for a microcontroller?

Answer: A voltage regulator (often an IC like the 7805). It’s a small chip that keeps the output voltage constant regardless of input variations.