Project Description: This project implements Integral Cycle Switching to control the power delivered to a linear AC load (like a heater) without introducing harmonics. An 8051-family microcontroller is used to achieve this by selectively allowing whole cycles of the AC mains voltage to pass through to the load. A zero-crossing detector (ZCD), typically using a comparator, provides an interrupt signal to the microcontroller at each zero-crossing point. Based on the desired power level (set by input switches), the microcontroller generates precise triggering pulses for a TRIAC (via opto-isolators for isolation). By removing whole cycles or specific integral portions of cycles, the time-average voltage to the load is reduced proportionally, effectively controlling the power while maintaining a high power factor and low harmonic distortion, which is critical for industrial applications like electric furnaces. A lamp is used as a stand-in for the actual high-power load for verification.
 
Hardware components: 
8051 Microcontroller (e.g., AT89S52/89C51)
Crystal Oscillator (11.0592 MHz or 12 MHz)
Capacitors (Assorted values: 33pF, 10$\mu$F, 100nF, etc.)
Resistors (Assorted values, ≈ 1/4W)
Voltage Regulator (7805)
Diodes (e.g., 1N4007 for rectifier)
Comparator IC (e.g., LM339 or LM358 for Zero-Crossing Detector)
Optocoupler/Opto-isolator (e.g., MOC3021/3041 for TRIAC)
TRIAC (e.g., BT136 or appropriate for load current)
Input Switches/Buttons (For power level selection)
Indicators (LEDs with current-limiting resistors)
AC Lamp/Bulb (Load substitute, e.g., 100W)
Transformer (9V or 12V step-down for power supply)
Rectifier/Filter PCB (General Purpose PCB)
Connecting Wires (Hook-up wire/PCB headers)
Power Socket/Terminals (AC input/output)
Fuse Holder and Fuse
 
Features
Harmonic-free power control: Operates by removing whole cycles, avoiding the introduction of higher-order harmonics common in phase control.
High Power Factor: Maintains a power factor close to unity, important for industrial loads.
Digital Control: Uses an 8051 microcontroller for precise and flexible control logic.
Zero-Crossing Detection (ZCD): Ensures switching occurs only at the AC signal's zero-crossing, minimizing voltage and current surges.
Electrical Isolation: Opto-isolators provide safety and separation between the low-voltage control circuit and the high-voltage AC load.
User-Defined Power Steps: Power level can be adjusted via simple input switches.
 
Applications
Industrial Heating Systems: Control of electric furnaces, ovens, and kilns.
Resistive Load Control: Managing power in any linear, resistive AC load (e.g., immersion heaters, industrial soldering irons).
Lighting Dimming (Non-LED/CFL): Controlling the power to traditional incandescent filament lamps.
Laboratory Power Control: Use as a stable, low-harmonic power regulator for test setups.
 
Project Includes:
Fully assembled and tested circuit
Circuit diagram
Source code 
(For DIY KITs - only the components will be provided)
 
Project Types:
DIY KIT(Do IT YourSelf KIT) - We are providing only components in this kit for this project
DIY KIT with Code & Circuit Connections - Along with the components, you will get the Code and the Circuit Connections file to help you build the project easily.
Readymade Breadboard - We are providing fully assembled, tested and ready-made project using plug-n-play jumper wires and breadboard with all the other components, code & circuit diagram.
Readymade Soldered - We are providing fully assembled, tested and ready-made project soldered on a PCB with all the other components, code & circuit diagram.
 
Dimensions
Approximate PCB Size: 10×8×3 cm (Excluding external load/lamp).
 
Shipping Dimensions
Estimated Box Size: 15(L)cm×12(W)cm×6(H)cm
 
Weight
Component Weight (Total): ≈100 grams.
 
Estimated Project Weight: 1kg
 
Notes: All the products are made by LearnElectronics India and not for re-sale.