Project Hub /Basic Analog & Power Electronics/Battery Chargers & Charging Circuits/Portable Solar Lantern Cum Bedlight

Beginner

ANALOG / DISCRETE

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

Portable Solar Lantern Cum Bedlight

A portable solar-powered lantern featuring an automatic bedlight mode using an LDR sensor, rechargeable via a solar panel or USB charger.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
2-Slot 18650 Holder with Protective Cover and On/Off Switch – Case Rs. 109.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: Battery (generic / unspecified)
Solar Panel
Transistors (BC547 / 2N2222 / TIP / MOSFET)
Diodes (1N4007 / 1N4148 / Schottky / Zener)
Custom PCB / PCB Fab
manual)

Browse all components

How It Works

The Portable Solar Lantern Cum Bedlight functions as an autonomous, dual-mode lighting system built around a custom PCB and an analog transistor circuit. At its core, a 5.5V, 60mA solar panel captures ambient light to generate electrical energy, which flows through 1N4007 rectifier diodes (D1, D2) to safely charge the 4V lead-acid battery without back-feeding current into the panel. An indicator LED (LED1) provides visual feedback on system status. The circuit features a manual and automatic operational mode controlled by switch S1. In the automatic bedlight mode, an LDR1 (Light Dependent Resistor) continuously monitors ambient room illumination. When daylight fades and darkness falls, the resistance of LDR1 increases, which alters the base voltage of the BC547 transistor (T1). Transistor T1 acts as an electronic switch; as the base voltage crosses the required threshold, T1 turns on, allowing current to flow through resistor R3 and illuminate the powerful 1-watt white LED (LED2). When ambient light returns in the morning, the LDR resistance drops, turning off the transistor and the 1-watt LED automatically. This creates a seamless transition from a daytime charging station to a nighttime bedside lamp.

Why Build This

Provides practical, emergency lighting and reliable household night lamps for areas with unstable grid power.

Serves as a hands-on introduction to harvesting renewable solar energy and storing it in rechargeable chemical batteries.

Demonstrates fundamental analog automation using optical sensors and discrete transistor switching instead of microcontrollers.

Real-World Application

Emergency lighting, household night lamps, portable outdoor lighting in areas with unreliable grid power.

Skills You'll Learn

analog circuit design

transistor switching

optical sensing with LDRs

battery charging management

power routing with diodes

Safety Precautions

Ensure proper polarity when connecting the lead-acid battery and solar panel to prevent circuit damage.

Technology Tags

SOLAR PANEL

LDR

BC547 TRANSISTOR

LED

1N4007 DIODE

LEAD-ACID BATTERY

PCB DESIGN

ANALOG ELECTRONICS

Frequently Asked Questions

Do I need to write any software or code for this project?

No, this is a purely analog circuit built using discrete components like transistors, diodes, and resistors, so no programming or software is required.

What is the purpose of the 1N4007 diodes in the circuit?

The diodes act as rectifiers to manage current flow, ensuring that electricity flows from the solar panel into the 4V battery to charge it, while preventing the battery from discharging backward through the solar panel when it is dark.

How does the LDR know when to turn on the bedlight?

The LDR changes its electrical resistance based on the amount of light hitting its surface. In the dark, its high resistance triggers the BC547 transistor to switch on power to the 1-watt white LED automatically.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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