Project idea
An AC power controller where a keypad percentage input drives the firing angle of a TRIAC to regulate load power, with a 16x2 LCD showing the set value in real time for clarity and calibration.
Phase-angle control adjusts the conduction portion of each AC half-cycle without changing amplitude, enabling smooth dimming or power throttling for lamps and other resistive loads.
Project description
An 8051 MCU reads user input from a 4x4 keypad, maps the percentage to a phase delay from the AC zero crossing, and triggers the TRIAC via a non–zero-cross opto-triac driver (MOC3021) to achieve precise power control.
The LCD interfaces to the 8051 to display the commanded power percentage, while the firmware uses zero-cross timing to compute per-cycle firing delays for stable, flicker-minimized output.
This approach is standard in phase-fired controllers, widely used for lamp dimming and heater control where accurate percentage-based regulation is desired.
Total list of components
8051 microcontroller (e.g., AT89S52, DIP-40)
11.0592 MHz crystal + load capacitors
16x2 character LCD (1602)
4x4 matrix keypad (tactile or membrane)
TRIAC (e.g., BT136 series)
Opto-triac driver MOC3021 (random-phase for dimming)
Basic zero-cross detect components (opto or comparator stage)
Diodes (e.g., 1N4007 for low-voltage rectification)
Resistors and capacitors (timing, pull-ups, filtering)
Transistors (general purpose for interfacing, as needed)
LEDs (power and status)
Push buttons (reset/menu, if desired)
Power regulation (e.g., 5 V rail for MCU/LCD)
IC sockets and headers
PCB or breadboard, cables and connectors
AC lamp load and holder for demonstration
Features
Percentage-based AC power setpoint via keypad with live LCD feedback for usability.
Phase-angle control for smooth, linear-feel dimming of resistive loads.
Opto-isolated gate drive using MOC3021 for robust mains isolation.
Zero-cross synchronized firing to minimize flicker and EMI.
Modular 8051 firmware structure for easy tuning and extension.
Applications
Lamp dimmers and studio lighting rigs requiring precise level control.
Resistive heater power throttling in test benches and labs.
Fan or universal motor control where phase-cut is acceptable.
Educational demonstration of thyristor/triac phase control.
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 in cm
A practical build fits on a ~20 × 15 × 5 cm base to accommodate the LCD footprint (~8.0 × 3.6 × 1.45 cm module) and safe spacing for the mains section.
This size allows keypad access, LCD visibility, isolation gaps, and a small heatsink for the TRIAC if needed.
Shipping dimensions in cm
Typical packaging of ~25 × 20 × 10 cm provides room for shock protection and separation of the mains-exposed assembly.
The extra margin ensures safe transport of the LCD and keypad while keeping the box compact for courier handling.
Weight
Assembled kit weight is approximately 0.6 kg considering PCB, LCD, keypad, passives, and TRIAC hardware.
Including protective packing, shipping weight is typically ~0.9 kg.
Estimate project weight
Hardware-only weight targeting ~0.6 kg offers good sturdiness without excessive bulk for student demos
Notes: All the products are made by LearnElectronics India and not for re-sale.
AC Power Strength Controller System
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Order Processing Time:
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Order Cancellations:
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Returns and Refunds:
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Technical Support:
- We provide basic technical support for the first 30 days after delivery to help you set up and operate your project.
- Extended support and customization services are available at an additional cost.
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Disclaimer:
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