Timer circuit

AC Stair Timer (High-Load AC Triggered Timer Circuit using NE555)

An affordable and energy-efficient timer circuit designed to control stairway lighting. The circuit is triggered by an AC signal from any stair switch and automatically turns off the light after a user-defined delay. It consumes no power while idle, thanks to a latch mechanism that cuts off the entire supply when the relay opens.

✅ Features

• AC Triggered: Can be triggered from any AC switch connected in the stairway.
• Zero Power Consumption in Standby: Power supply is wired in series with the load. Once the relay disconnects the load, the entire circuit powers off.
• Handles up to 10A Load: Suitable for high-power lighting circuits.
• Adjustable Timer (0–15 min): Controlled by a potentiometer. Can be extended using standard NE555 timing calculations.
• Low-Cost and Simple Components: Built around NE555, a relay, and basic resistors/capacitors.
• Single-Layer PCB: Easy for home etching or low-cost fabrication.
• Local Alternative to Imported Units: Provides the same functionality at a fraction of the cost.

🧩 Main Components

• NE555 Timer IC
• Relay (10A rated)
• Potentiometer
• Capacitors and resistors

⏱️ Time Adjustment Formula

You can calculate or extend the timing duration using the standard NE555 monostable formula:

T ≈ 1.1 × R × C

Where:

• R is the potentiometer (resistance in ohms)
• C is the timing capacitor (in farads)

📁 Project Files

• KiCad design files (schematic + PCB layout)
• Proteus simulation file
• STEP file (3D model of assembled circuit)
• PDFs for manual PCB etching (Top layer, Drill, Silkscreen)
• Real-life assembly images

🧪 Project Status

• ✅ Version 1 tested successfully in a real stairway.
• 🛠️ Version 2 in development with enhancements.

⚠️ Safety Notes

• Ensure proper isolation when connecting to AC.
• Add relay cooling if switching high loads frequently.

📜 License

This project is open source.

📷 Images

📬 Contact

Mohamed Abdelhady — For inquiries, feel free to reach out if any issue arises.