PC Table Lamp
This practical circuit for a table lamp is based on the well-known timer integrated circuit (IC) TLC555. When your computer is turned "on," it triggers the activation of an electric bulb.…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
PC Table Lamp is a electronics project. This practical circuit for a table lamp is based on the well-known timer integrated circuit (IC) TLC555. When your computer is turned "on," it triggers the activation of an electric bulb.…
- Source pages
- 277-279
- Named parts
- 1
- 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.
- This project may involve hazardous voltage. Work only with qualified supervision and proper isolation.
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
Transformer
A power component supplies, converts, stores, or regulates energy for the project.
What it does hereIt must provide the documented voltage, polarity, isolation, and sufficient current safely.
Buy / compare this part ↗Advantages
- Stable power improves reliability
- Current limiting protects first tests
- Regulation reduces resets and noise
Limitations
- Wrong polarity can cause immediate damage
- Underrated parts overheat
- Mains circuits require qualified supervision
Handling
- Measure output before connection
- Use a fuse or current limit
- Insulate exposed conductors
Specifications to verify
- Use the exact model, value, package, and rating listed for Transformer; similar-looking parts are not always interchangeable.
- Confirm input/output voltage, current, polarity, connector, isolation, and thermal rating.
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.
PC Table Lamp: 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 practical circuit for a table lamp is based on the well-known timer integrated circuit (IC) TLC555. When your computer is turned "on," it triggers the activation of an electric bulb. When you turn off the computer, the bulb will likewise go into an "off" state by itself. Table lamp circuit
The usage of a step-down transformer in the power part of the circuit has been purposefully eliminated to eliminate the risk of electromagnetic radiation. This was done in order to avoid the danger of electromagnetic radiation. Instead, a capacitive potential divider is utilized to lower the supply voltage before sending it to the rectifier circuit. This results in the control circuit receiving the necessary operating voltage of 5V DC. The most important component of this arrangement is the capacitor C5. Even though there is an AC mains supply available, the output pin 3 of IC2 is low when the PC is in the "off" state; as a result, TRIAC1 does not conduct. In order to separate the PC from the control circuit of the table lamp, optocoupler IC1 is being utilized in this situation. Bypassing the USB port's fluctuations is made possible by capacitor C1. The input current is controlled by the resistor labeled R1. When the personal computer is turned "on," 5V DC is drawn from the USB port and applied to optocoupler MCT2E (IC1). This causes the component to conduct. This causes the input to pins 2 and 6 of IC2 to be pulled down. As a direct consequence of this, the output of IC2 becomes high, which causes TRIAC1 to be activated via resistor R3 and diode D4. With this, the supply to lamp L1 is finished, and the lamp now lights up. As soon as the personal computer is turned off, the input to the optocoupler is turned off as well. This causes the control circuit to stop working, as the input pins 2 and 6 of the timer IC go high while the output pin 3 goes low. The light in the room goes out.
Construction & testing
Project build noteUsing a common USB cable that has an A-type connector on one end and a B-type connector on the other end, assemble the circuit on a general purpose printed circuit board (PCB), and then connect the input point of the device to an empty USB port on the personal computer (PC). Take note that the PC-status detection only makes use of the 5V DC supply that is provided by the USB connection here. The gadget receives 230V AC as its source of power, which is then lowered by a mixture of capacitors and resistors and rectified by diodes D2 and D3. Due to the fact that the gadget is so diminutive, it can be readily concealed within the base of an elegant table lamp.
You built PC Table Lamp.
You followed the full workflow from understanding the mission to testing the finished project. That is a real engineering achievement - well done.
Audible Continuity Tester
Ready to reuse what you learned in another project from the same track?
Start this project →