Siksha Sarovar

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Siksha Sarovar is a free e-learning platform for coding courses, BCA university notes and competitive exam preparation. Optional Google sign-in saves your learning progress across devices.

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2.2 Actuators: Interacting with the Physical World

Lesson 8 of 31 in the free Internet of Things (IoT) notes on Siksha Sarovar, written by Rohit Jangra.

2.2.1 Principles of Actuation in IoT

Actuators are the "Physical Muscles" of an IoT system. They receive digital commands from the controller and perform mechanical work, light emission, or heat generation.

2.2.2 Actuator Categorization and Control Logic Matrix

Actuator TypePower SourcePhysicsTypical IoT ApplicationControl Logic
DC MotorElectricalLorentz ForceSmart Fans, Toy robotsPWM (Speed)
Stepper MotorElectricalPulse sequence3D Printers, Precision LocksStep frequency
Servo MotorElectricalFeedback PWMRobotic arms, Camera GimbalsDuty Cycle (Angle)
RelayElectromagneticSolenoid switchSwitching AC Geysers/LightsGPIO High/Low
SolenoidElectromagneticMagnetic plungerSmart Water Valves, Door latchesGPIO pulse
PneumaticCompressed AirPressure differentialFactory assembly linesSolenoid valve

2.2.3 Driving Heavy Loads: The Transistor Bridge

Microcontrollers (MCUs) like Arduino can typically only output 20mA to 40mA per pin. Actuators need Amps.

  • MOSFET Switches: For high-speed switching of DC loads (Motor speed, LED dimming).
  • Relay Modules: Providing complete physical isolation between the low-voltage DC circuit and high-voltage AC (220V).
  • H-Bridge (L298N): A specialized dual-bridge circuit used to control the speed and direction of two DC motors simultaneously.

2.2.4 PWM (Pulse Width Modulation) Theory and Math

PWM is the universal method for controlling actuator "Intensity". By switching the signal ON and OFF at high frequencies (e.g., 1kHz), we control the "Average Voltage". Mathematical Definition: $V_{avg} = V_{peak} imes ( rac{T_{on}}{T_{on} + T_{off}})$