Demo Circuit for Over-Voltage Protection
Circuits designed to protect voltage-sensitive loads from excessive voltage are called over-voltage protection circuits. Transients in voltage can be caused by a variety of factors, inclu…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
Demo Circuit for Over-Voltage Protection is a electronics project. Circuits designed to protect voltage-sensitive loads from excessive voltage are called over-voltage protection circuits. Transients in voltage can be caused by a variety of factors, inclu…
- Source pages
- 274-276
- Named parts
- 5
- 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
Potentiometer
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 Potentiometer; 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
PASSIVE LEARNING VIEW1N4007
A passive component sets current, voltage, timing, filtering, or signal behaviour without adding gain.
What it does hereIts exact value and tolerance determine how the surrounding stage behaves.
Buy / compare this part ↗Advantages
- Simple and dependable
- Low cost
- Easy to measure before installation
Limitations
- A wrong value can stop or damage the circuit
- Ratings must not be exceeded
- Polarized parts require correct orientation
Handling
- Measure unclear values
- Observe capacitor polarity
- Avoid overheating leads while soldering
Specifications to verify
- Use the exact model, value, package, and rating listed for 1N4007; similar-looking parts are not always interchangeable.
- Confirm value, tolerance, power or voltage rating, polarity, and package size.
What's this?Image, role, pros, cons, handling & specifications
SEMICONDUCTOR LEARNING VIEWBC548
A semiconductor stage performs switching, amplification, regulation, rectification, or logic.
What it does hereIt controls current or signal flow at a defined point in the circuit.
Buy / compare this part ↗Advantages
- Fast and efficient
- Compact
- Can control larger loads from smaller signals
Limitations
- Pin order varies
- Sensitive to overvoltage and reverse polarity
- May need cooling or bias components
Handling
- Verify the datasheet pinout
- Avoid static and soldering heat
- Check notch, stripe, or flat-face orientation
Specifications to verify
- Use the exact model, value, package, and rating listed for BC548; similar-looking parts are not always interchangeable.
- Confirm pinout, maximum voltage/current, dissipation, gain or forward voltage, and package.
What's this?Image, role, pros, cons, handling & specifications
T1 - transistor stage identified in the circuit
A semiconductor stage performs switching, amplification, regulation, rectification, or logic.
What it does hereIt controls current or signal flow at a defined point in the circuit.
Buy / compare this part ↗Advantages
- Fast and efficient
- Compact
- Can control larger loads from smaller signals
Limitations
- Pin order varies
- Sensitive to overvoltage and reverse polarity
- May need cooling or bias components
Handling
- Verify the datasheet pinout
- Avoid static and soldering heat
- Check notch, stripe, or flat-face orientation
Specifications to verify
- Use the exact model, value, package, and rating listed for T1 - transistor stage identified in the circuit; similar-looking parts are not always interchangeable.
- Confirm pinout, maximum voltage/current, dissipation, gain or forward voltage, and package.
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.
Demo Circuit for Over-Voltage Protection: 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 noteCircuits designed to protect voltage-sensitive loads from excessive voltage are called over-voltage protection circuits. Transients in voltage can be caused by a variety of factors, including the switching of loads and transformers, as well as short circuits and
open circuits in the rectifier circuit and the regulator circuit. These kinds of transients have the potential to disrupt the normal operation of an electrical circuit or perhaps cause it to become damaged. As a result, the use of an over-voltage protection circuit is obligatory for the purpose of shielding expensive loads from any and all sources of voltage transients. Students who are studying electronics engineering and are required to complete an experiment on over-voltage protection as part of their coursework can use the circuit that is currently being discussed to perform a highly convincing demonstration of the effect. Circuit and the working The demonstration circuit for the over-voltage protection is shown in the figure. A rectifier consisting of four 1N4007 diodes (D1 through D4), a 10V voltage regulator IC 7810 (IC1), an SCR 2P4M (SCR1), a transistor BC548 (T1), and a few additional components are used to construct it. In order to provide protection, SCR1 is utilized. If the voltage is higher than what the device that needs to be protected can withstand (a 6V bulb in this case), the circuit will cut the gadget off from its supply. In order to demonstrate this, a potentiometer named VR1 is linked across regulator IC1, and this connection is utilized to raise the voltage that is produced by regulator IC1. When the voltage at the output of IC1 rises, the voltage at the base of transistor T1 likewise rises. This causes SCR1 to become activated through the medium of resistor R6. When
SCR1 is activated, the fuse will blow, which will cut off the device's connection to the power source. Turn on the circuit once you have set VR1 so that it is at its highest possible setting (let's say, 1k). Take a reading of the output with a digital multimeter at the CON3 terminal. It needs to be somewhere around 10.3 V. Now, gradually lessen the resistance of VR1. The multimeter displays 10.9 V when it is read at around 800. Continue to lower the resistance until the SCR1 relay opens. Following the delivery of a triggering pulse, it was discovered through experimentation that the SCR activates at a resistance of approximately 680, causing a substantial current to flow through the fuse wire. This causes the fuse wire to blow, which in turn causes the load to become disconnected from the supply.
You built Demo Circuit for Over-Voltage Protection.
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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