Why build a solar light?

A simple no-microcontroller solar light is the best choice for long-term reliability. Fewer components = fewer failure points. Perfect for:

• Balcony lighting
• Garden / pathway lighting
• Gate / stairway illumination
• Emergency backup lighting

Build time: 1 hour • Skill required: Beginner

Parts & recommended buys

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Solar Panel — 5W to 10W

Best for charging small Li-ion or SLA batteries. Mono panels = more efficient.

• Recommended: 6V 5W / 12V 10W
• Weatherproof, long life

₹600 – ₹1,500
Buy on Amazon

Solar Charge Controller / TP4056

Controls charging & protects battery from overcharge/discharge.

• For Li-ion: TP4056 + protection
• For SLA: Small 12V PWM controller

₹200 – ₹900
Buy on Amazon

Battery — Li-ion 18650 / SLA

Use quality cells for longer runtime and durability.

• Li-ion 18650 (3.7V)
• SLA 12V for larger systems

₹400 – ₹2,500
Buy on Amazon

LED Module — COB / SMD

1W–5W LEDs are ideal for bright and efficient lighting.

• 3000K–4000K recommended
• Use LED driver for protection

₹150 – ₹800
Buy on Amazon

LDR Dusk-to-Dawn Switch

Automatically lights up at night and turns off at sunrise.

• Beginner-friendly module
• Relay or transistor output

₹80 – ₹300
Buy on Amazon

Misc Items

Wires, enclosure, heat-shrink, silicone sealant, screws, brackets.

₹200 – ₹800
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Total cost: ₹1,500 – ₹6,000 depending on battery + panel size.

How it works

During daytime, the solar panel charges the battery using the charge controller. At dusk, the LDR senses darkness and automatically switches the LED ON. At dawn, it turns OFF.

Step-by-step assembly

1. Mount the solar panel — Face south, tilt 20–30°.
2. Place battery & controller inside a waterproof box.
3. Connect solar panel → controller input (observe polarity).
4. Connect controller output → battery terminals.
5. Connect LED through LDR relay / transistor.
6. Test LDR by covering it — LED should turn ON.
7. Seal enclosure using silicone for waterproofing.

Wiring diagram

  [SOLAR PANEL] ---> [CHARGE CONTROLLER] ---> [BATTERY]
                                   |
                                   |--> [LDR MODULE] --> (Relay/Transistor) --> [LED]
    

Example for TP4056 Li-ion charging:

  Solar 5V -> TP4056 IN+
  Solar GND -> TP4056 IN-
  TP4056 B+ -> Battery +
  TP4056 B- -> Battery -
  Battery + -> LED via LDR Switch
  Battery - -> LED -
    

Testing & commissioning

1. Place panel in sun → battery should charge.
2. Cover LDR → LED should turn ON instantly.
3. Measure LED current to estimate runtime.
4. Adjust LDR sensitivity using onboard potentiometer.

Troubleshooting

• LED not turning ON: Check LDR module polarity & battery charge.
• Low brightness: Battery weak / LED current too low.
• Not charging: Wrong polarity or weak sunlight.
• LDR false triggering: Keep away from other lights.

FAQs