Electronic Fuse
A workbench power supply is an item that ought to be included in each and every electronics workshop. The power supply needs to have a regulator installed, as well as some kind of protect…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
Electronic Fuse is a electronics project. A workbench power supply is an item that ought to be included in each and every electronics workshop. The power supply needs to have a regulator installed, as well as some kind of protect…
- Source pages
- 123-124
- 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.
- 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
Buzzer
An output component turns an electrical control signal into light, sound, motion, switching, or displayed information.
What it does hereIt presents the circuit result or acts on the physical world.
Buy / compare this part ↗Advantages
- Makes system state visible
- Can be tested separately
- Supports clear troubleshooting
Limitations
- Loads may exceed controller current
- Polarity or driver direction can matter
- Inductive loads create voltage spikes
Handling
- Use the documented driver stage
- Check polarity and load current
- Add flyback protection for inductive loads
Specifications to verify
- Use the exact model, value, package, and rating listed for Buzzer; similar-looking parts are not always interchangeable.
- Confirm voltage, current, polarity, interface, driver requirements, and duty cycle.
What's this?Image, role, pros, cons, handling & specifications
Power supply
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 Power supply; similar-looking parts are not always interchangeable.
- Confirm input/output voltage, current, polarity, connector, isolation, and thermal rating.
What's this?Image, role, pros, cons, handling & specifications
LED1, LED2 - indicator LEDs 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 LED1, LED2 - indicator LEDs 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.
Electronic Fuse: 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 noteA workbench power supply is an item that ought to be included in each and every electronics workshop. The power supply needs to have a regulator installed, as well as some kind of protection against short circuits. For current detection, the vast majority of power supply protection circuits make use of a resistor with a low value and a high wattage that is linked in series with the load. When determining whether or not to activate the protective circuit, the voltage drop that occurs across the sensor resistor is taken into consideration. A poly-fuse application, also known as a re-settable fuse by itself, serves as the foundation for the electronic fuse circuit that has been described here. Circuit operation
When the electricity is first applied to the circuit, the silicon-controlled rectifier SCR1 is in its "off" position. The load is connected to the normally opened (N/O) contact of relay RL1, which is energized by the polyfuse. Relay RL1 receives its power from the polyfuse. When the load's current draw exceeds a certain threshold value (which is dependent on the number of turns in the winding on the reed relay; see Figure 2 and the accompanying table for further information), the contacts of the reed relay RL2 will close, which will cause the SCR1 to be triggered. As a direct consequence of this, relay RL1 becomes de-energized, and the load is severed. Up to the point where SCR1 is deactivated, the polyfuse will maintain its high-resistance state. Either turning off the power supply or pressing the S1 reset switch will reset the circuit. Both of these options are available. That the power supply is operating normally can be seen by the LED2 indicator. The user is being alerted through the use of a buzzer when the power supply unit enters the protection mode, which is indicated by the LED1 light. Because the turns of the reed relay winding are determined by the current that flows through the load, you should consult the table for winding specifics that correspond to the requirements you have for the load current. At EFY, testing was carried out for an AC load current of approximately 1.85A at 230V AC mains. As a result, 16 turns of 22SWG copper-enameled wire were wound on the reed relay.
You built Electronic Fuse.
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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