unit 2

 

📌 1. Define Sensor

A sensor is a device that detects physical changes and converts them into electrical signals.

👉 Simple: Sensor = “Sense + Send Data”

Examples:

  • Temperature sensor

  • Light sensor

  • Motion sensor

  • Gas sensor

🧩 2. Basic Components of a Sensor Node

A sensor node is a small smart device used in IoT.

Main parts:

  1. 🔎 Sensor Unit – collects data

  2. 🧠 Microcontroller – processes data

  3. 📡 Communication Module – WiFi/Bluetooth

  4. 🔋 Power Supply – battery

👉 Think: Sensor + Brain + Internet + Battery

⚠️ 3. Challenges of Sensor Node

Common problems:

  • 🔋 Limited battery power

  • 📶 Network issues

  • 📏 Accuracy problems

  • 🌡️ Environmental effects

  • 💾 Limited memory & processing

⭐ 4. Sensor Features

Important characteristics:

  • Accuracy – correct measurement

  • Sensitivity – detects small change

  • Range – minimum to maximum value

  • Response Time – speed of sensing

  • Stability – same result over time

📐 5. Sensor Resolution

Resolution = smallest change a sensor can detect.

👉 Example:
If sensor shows 0.1°C change → high resolution.

🧪 6. Sensor Classes

🔌 Analog Sensors

  • Output is continuous signal

  • Example: Temperature (LM35)

💻 Digital Sensors

  • Output is 0 or 1 (ON/OFF)

  • Example: IR sensor

📊 Scalar Sensors

  • Measure only magnitude

  • Example: Temperature sensor

🧭 Vector Sensors

  • Measure magnitude + direction

  • Example: Accelerometer

🔍 7. Sensor Types

Some common IoT sensors:

  • Temperature sensor

  • Humidity sensor

  • Pressure sensor

  • Light sensor

  • Motion sensor

  • Gas sensor

⚠️ 8. Sensor Errors (Very Important for Exams)

🎯 Bias Error

Constant difference from actual value.

👉 Example: Always +2°C higher reading.

📉 Drift

Sensor output slowly changes over time even if input is same.

🔄 Hysteresis Error

Output depends on previous value or direction of change.

🔢 Quantization Error

Error caused due to digital conversion (rounding values).

⚙️ 9. Actuator

An actuator is a device that converts electrical signal into physical action.

👉 Simple:
Sensor = detect
Actuator = perform action

Examples:

  • Motor

  • Fan

  • Valve

  • LED

🏭 10. Actuator Types

💧 Hydraulic Actuator

Uses liquid pressure.
👉 Used in heavy machines.

💨 Pneumatic Actuator

Uses air pressure.
👉 Used in automation industries.

⚡ Electrical Actuator

Uses electricity.
👉 Motors, relays, solenoids.

🔥 Thermal / 🧲 Magnetic Actuator

  • Thermal → heat based movement

  • Magnetic → magnetic field movement

⚙️ Mechanical Actuator

Uses gears, springs, levers.

🧬 Soft Actuators

Flexible materials (rubber/polymer).
👉 Used in robotics & wearable tech.

🧠 Easy Exam Trick (Remember)

👉 Sensor = Input device
👉 Actuator = Output device

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