Battery-Powered Night Lamp Using an Old LED Bulb
This circuit makes a battery-powered night light out of a cheap 3W LED board. This board has eight SMD2835 LEDs that are all wired together in a series. For proper lighting, brand-name LE…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
Battery-Powered Night Lamp Using an Old LED Bulb is a electronics project. This circuit makes a battery-powered night light out of a cheap 3W LED board. This board has eight SMD2835 LEDs that are all wired together in a series. For proper lighting, brand-name LE…
- Source pages
- 561-563
- Named parts
- 3
- Build goal
- Working, tested prototype
Tools you need
- Digital multimeter
- Wire stripper and side cutters
- Soldering iron with a fine tip
- Current-limited bench supply
Use eye protection, good lighting, and a clean insulated surface throughout the build.
Safety precautions
- Disconnect every power source before changing a connection.
- Check component polarity, pinout, and supply voltage twice.
- Use a current limit for the first power-up.
- Keep liquids, loose metal, and uninsulated wires away from the bench.
Gather, identify, and understand every part.
Use the standardized inventory, then open What's this? to learn each part's role, advantages, limitations, handling, and specifications.
What's this?Image, role, pros, cons, handling & specifications
Operational amplifier
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for Operational amplifier; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
What's this?Image, role, pros, cons, handling & specifications
MAXIMUM
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for MAXIMUM; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
What's this?Image, role, pros, cons, handling & specifications
PART LEARNING VIEWVR1 - preset potentiometer identified in the circuit
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for VR1 - preset potentiometer identified in the circuit; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
Connect one verified path at a time.
Explore the named components and standardized signal flow, then use Source Check to verify exact physical pins, values, and topology before applying power.
Trace this circuit.
Battery-Powered Night Lamp Using an Old LED Bulb: interactive parts, standardized terminals, responsive anchored wires, student explanations, and the original circuit reference in one shared system.
Trace before wiring
Follow power, ground, inputs, processing, and outputs in that order. Never guess a pin from package shape alone.
Connect with power off
Make short, labelled connections and share a common ground only where the schematic requires it.
Inspect every joint
Check continuity, polarity, adjacent shorts, and loose connections before the first power-up.
Open all source diagrams and build views 1 visuals
Confirm the hardware-only control path.
This project does not include firmware in the source. The circuit itself provides the required behaviour.
How to connect
- Match every controller label to the circuit view and source pin map.
- Join grounds before signal wires when separate low-voltage supplies are used.
- Keep motors, relays, pumps, and other loads on a suitable driver and external supply.
Common mistakes
Reversed VCC/GND, board-label versus GPIO-number confusion, missing common ground, and charge-only USB cables.
Troubleshoot
Disconnect loads, continuity-test one path at a time, then test with a current limit.
Software preparation
No IDE, board package, library, or firmware upload is required for this project.
If you add a programmable controller as an extension, document its pin map separately.
How to upload code
The original design is implemented entirely in hardware, so proceed after verifying the circuit and supply.
Assemble, deploy, test, and troubleshoot.
Use the complete source notes in build order, then pass the final checks before calling the project finished.
Build in functional stages
- Power and regulation
- Controller or processing stage
- Inputs and sensors
- Outputs and loads
- Enclosure and strain relief
Power up safely
- Inspect unpowered continuity first
- Apply the lowest safe current limit
- Measure supply rails before signals
- Add one load at a time
- Record expected and actual results
Work from simple to complex
- Confirm power, ground, polarity, and orientation
- Compare each pin with the source
- Test inputs separately from outputs
- Replace only one variable at a time
- Power off before every correction
Follow the documented instructions.
These notes come from this project's source and remain in their original order.
Project overview
Project build noteThis circuit makes a battery-powered night light out of a cheap 3W LED board. This board has eight SMD2835 LEDs that are all wired together in a
series. For proper lighting, brand-name LED bulbs have SMPS drivers and protection circuits. But some cheap LED bulbs get their power from capacitors and don't have any safety circuits. In this project, a switching regulator system called a 78S40 IC is used. Fig. 1: Circuit diagram of battery-powered night lamp using an old LED bulb SMD2835 LED module SMD2835 is a new packaging structure with a self-heat-sink design and a high-efficiency LED module. It is used in many different kinds of lighting, including general, commercial, industrial, city, and car lighting. Here are some of the things it has.
Vertical structure Chips with direct conduction fins are better at getting rid of heat, so they can handle more current (40-60mA).
A big heat sinks The heat sink is 2-3 times bigger than SMD3528 and has a great design for getting rid of heat. Large light-emitting surface This improves the efficiency of light up to 90 per cent. Cost: Even though SMD2835 is 25% less expensive than SMD3528, it can produce the same amount of light. The circuit in Fig. 1 is made up of a 78S40 DC-DC converter IC (IC1), eight high-bright SMD2835 LEDs (from an old LED bulb), and a few other parts. In this case, IC1 is set up as a changed boost converter. It does both boosting and driving a constant current. IC1 is in a 16-pin dual inline package that lets a reference and a non-inverting input of the comparator be pinned out. These extra features give this part a lot more flexibility and make it possible to use it in more complex applications. Voltage boosting is done by IC1, L1, and the circuitry on the LED board itself. Sense resistor R5, which is connected in series on the LED board, is used to measure the voltage drop across it. This is done to control the current. Since the maximum voltage across the sense resistor is less than one volt, the on-chip operational amplifier is used to boost the sense voltage for feedback. The frequency at which the circuit works is set by capacitor C1. With preset VR1, you can change how bright the LED is. With switch S1, the LED board can be turned on or off.
You built Battery-Powered Night Lamp Using an Old LED Bulb.
You followed the full workflow from understanding the mission to testing the finished project. That is a real engineering achievement - well done.
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