A solar street light controller using Arduino provides automatic dusk-to-dawn LED lighting powered entirely by solar energy. This project is ideal for illuminating driveways, garden paths, compound walls, and rural roads in India without any electricity connection. The Arduino adds intelligent features like brightness control, motion detection, and battery protection that go beyond simple on/off operation.
Table of Contents
- System Overview
- Components Needed
- Solar Panel and Battery Sizing
- LED Selection and Driver
- Arduino Control Logic
- Advanced Features
- Frequently Asked Questions
- Conclusion
System Overview
A solar street light system consists of:
- Solar panel: Charges the battery during daytime
- Battery: Stores energy for nighttime operation
- Arduino controller: Manages charging, light control, and protection
- LED module: The light source
- LDR sensor: Detects daylight/darkness for automatic switching
- PIR sensor (optional): Motion detection for energy-saving operation
Components Needed
- Arduino Nano (compact for enclosure mounting)
- 12V 20W solar panel
- 12V 7Ah sealed lead-acid or 12V 6Ah LiFePO4 battery
- 10W-30W LED floodlight or LED module (12V DC)
- LDR (light dependent resistor) + 10K resistor
- PIR motion sensor (HC-SR501) — optional
- IRFZ44N MOSFET for LED switching
- 1N4007 diode (reverse current protection)
- Voltage divider (100K + 33K) for battery monitoring
- Relay or MOSFET for solar panel disconnect
Solar Panel and Battery Sizing
For a 10W LED Operating 10 Hours
Daily energy need: 10W x 10h = 100Wh
Battery sizing (lead-acid, 50% DoD): 100 / 0.5 / 12 = 16.7Ah. A 12V 20Ah battery provides 1.2 days of autonomy.
Solar panel sizing: 100Wh / (5h sun x 0.8 efficiency) = 25W. A 30W panel provides margin for cloudy days.
LED Selection and Driver
For street lighting applications, choose high-efficiency LEDs:
- 10W LED (900 lumens): Suitable for pathway and garden lighting
- 20W LED (1800 lumens): Good for compound and small road lighting
- 30W LED (2700 lumens): Adequate for street and parking lot lighting
Use 12V DC LED modules or LED strips to avoid the need for an AC inverter. Drive them through a MOSFET (IRFZ44N) controlled by the Arduino’s PWM output for brightness adjustment.
Arduino Control Logic
The controller implements several intelligent features:
Dusk/Dawn Detection
The LDR reads ambient light levels. When light drops below a threshold (dusk), the LED turns on. When light rises above a threshold (dawn), the LED turns off. Use hysteresis (different on/off thresholds) to prevent flickering at the transition.
Battery Protection
Monitor battery voltage through a voltage divider. If the battery voltage drops below the low-voltage threshold (11.5V for lead-acid, 10.5V for LiFePO4), turn off the LED to prevent deep discharge. Resume when voltage recovers above 12.5V (from solar charging).
Overcharge Protection
When the battery reaches full charge (14.4V for lead-acid, 14.6V for LiFePO4), disconnect the solar panel using a relay or MOSFET. Reconnect when voltage drops below 13.5V.
Advanced Features
Motion-Activated Brightness
Run the LED at 30% brightness normally. When the PIR sensor detects motion, ramp up to 100% for 30-60 seconds, then fade back to 30%. This can extend battery life by 2-3x while still providing full illumination when needed.
Timed Dimming
Add an RTC (DS3231) module for time-aware dimming: 100% brightness from dusk to 10 PM, 50% from 10 PM to 4 AM, 100% from 4 AM to dawn. This conserves battery for the quieter overnight hours.
Battery Voltage Logging
Log battery voltage at regular intervals to track battery health over time. Declining maximum charge voltage indicates battery ageing.
Frequently Asked Questions
How bright is a 10W LED solar street light?
A 10W LED produces approximately 900-1000 lumens, equivalent to a 75W incandescent bulb. This is sufficient for illuminating a 3-4 metre radius on a pathway or driveway. For broader coverage, use 20W or 30W LEDs.
Will the system work during monsoon?
During heavy monsoon with limited sunlight, the battery may not fully recharge each day. The motion-activated brightness feature helps by reducing average power consumption. A 2-day battery autonomy ensures the light works through most cloudy stretches.
How long does the battery last?
Lead-acid batteries in daily cycling applications last 1-2 years. LiFePO4 batteries last 5-8 years. For street lights, LiFePO4 is the better investment despite the higher upfront cost.
Conclusion
An Arduino-based solar street light controller is a practical project that provides real value for homes, farms, and rural communities in India. The intelligent features — automatic dusk-to-dawn operation, motion-activated brightness, and battery protection — ensure reliable, efficient lighting without any electricity bills. Find Arduino boards, LED strips, sensors, and power components at Zbotic’s online store.
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