ElectraGuard: High and Low Voltage Cut Off With Delay and Alarm

The Electraguard is a reliable voltage protection device designed to safeguard electrical equipment from fluctuations in power supply due to voltage fluctuations. This compact and user-friendly system automatically disconnects electrical devices from the power source when voltage levels exceed predefined upper or lower limits, preventing potential damage.

The product is equipped with a delay mechanism to filter out short-term voltage spikes or drops, ensuring that transient disturbances do not unnecessarily disrupt the operation. It also features a visual and auditory alarm system to alert users during voltage anomalies. Once the voltage stabilizes within safe levels, the device automatically restores power to the connected equipment, ensuring uninterrupted functionality.

This device is inexpensive and built with readily available components, making it simple to maintain and repair. It is ideal for residential, commercial, and industrial applications where safeguarding sensitive electrical equipment is important to reducing downtime and improving safety.

Here are the materials used in this build:

1. Voltage Sensing Circuit Components: Op Amp IC TL072
2. Timer Circuit: NE555 Timer IC
3. Logic Section Components: NAND Gate IC CD4011
4. Relays: 9V Relay RL0260
5. LED Indicators: Red, Amber, and Green LEDs
6. Buzzer: For auditory alarms
7. Power Supply Unit: Converts 230V AC to 9V DC (regulated) and 15V DC (unregulated)
8. Dot Board: For building the prototype
9. Miscellaneous: Wires, solder, screws, and enclosure

The block diagram provides a clear and precise blueprint for understanding how the ElectraGuard's various parts function together. It helps to visualise the entire system by demonstrating how each component interacts and contributes to overall functionality. This diagram serves as a guide, ensuring that all subsystems are well-organised and have clearly defined functions, making it easier to plan, troubleshoot, and improve the project.

The power supply section was developed using a dual power output configuration to ensure that the sensor and control circuits work properly and without interference. The power input is 230V AC, and the Sense Power Supply (A) provides a steady voltage reference for the voltage sensing circuit. The System Power Supply (B) supplies the logic, comparator circuits, and other system components.

The voltage comparators are the system's primary detecting mechanism for voltage anomalies. The Low Voltage Comparator receives the Sense Power Supply (A) and the specified voltage reference, then compares the input voltage to the lower threshold. If the voltage is less than the threshold, it generates a low voltage sense (digital) signal. Furthermore, the High Voltage Comparator acts in a similar manner, comparing the input voltage to the upper threshold and producing a high voltage sense (digital) signal if the input exceeds the upper limit.

The logic part examines signals from both comparators and determines the necessary reactions, such as turning on the LED indicators for status display, triggering the buzzer for auditory alerts, and regulating the load relay to disconnect or reconnect the load as needed.

Timers in this design offer a delay before reactivating the relay, ensuring that transient voltage spikes do not cause unwanted load disconnections, and they are utilised to govern the timing for buzzer and indicator activities, resulting in consistent alarm signals.

The ElectraGuard prototype was constructed on a dot board and extensively tested to guarantee its functionality after the system was designed using the block diagram.

A permanent yet flexible platform for putting the circuit together was offered by the dot board. According to the block diagram, every component—including the buzzer, logic gates, timer integrated circuits, relays, LEDs, and voltage comparators—was arranged on the board. To guarantee correct operation, important parts including the Op Amp IC TL072, NAND Gate ICs (CD4011), and NE555 Timer ICs were arranged thoughtfully on the board. LEDs, the buzzer, and the relay were all placed in easily accessible areas for simpler testing and connecting. All parts were firmly soldered to the dot board after the placement was determined. In order to prevent short circuits or signal interference, connections were kept tidy and insulated.

After completion of soldering the prototype was powered by supplying 230V AC to the input. The power supply module generated the expected 9V and 15V outputs. Then a variable power supply was used to simulate different voltage conditions and tested the following status.

1. Normal Voltage: The green LED lit up, indicating normal operation. No alarms were triggered, and the relay remained engaged.
2. Low Voltage: When the input voltage dropped below the set threshold (216.2V) the relay disconnected the load and the amber LED lit up with the buzzer emitting intermittent sounds.
3. High Voltage: When the input voltage rose above the set threshold (243.8V) the relay disconnected the load and the red LED lit up with the buzzer emitting continuous sound.

When the voltage was restored the load was connected after a 10-second delay as planned.

Following the prototype's construction and testing, a thorough schematic diagram had to be made. An illustration of the circuit that shows how all the parts are connected and work together is called a schematic. It is essential for troubleshooting as well as documentation.

List the Components:

1. The first step was to identify all the components needed, such as the comparators, timer ICs, relay, LEDs, buzzer, and power supply. Each of these was represented with its standard symbol (e.g., triangles for comparators, rectangles for ICs, circles for LEDs).

Power Supply Setup:

1. The schematic started with the AC input (230V), which connects to the power supply. This power supply is responsible for converting the AC into the required 9V DC for the control circuits and 15V DC for the voltage sensing circuits.

Voltage Comparators:

1. Next, the low and high voltage comparators were added. These comparators take the input voltage and compare it to preset limits, then send signals to the logic section indicating whether the voltage is too high or too low.

Logic Section:

1. The logic section receives signals from the comparators and decides what actions to take. This section controls the relay to disconnect or reconnect the load, and triggers the LED indicators and buzzer based on the voltage level.

Relay and Load Control:

1. The relay is connected to the logic section and controls whether the load (in this case, the CFL bulb) is powered or not. If the voltage is out of range, the relay disconnects the load; once the voltage returns to safe levels, it reconnects.

Alarm System (LEDs and Buzzer):

1. The LED indicators were added to visually show the system’s status: a green LED for normal voltage, an amber one for low voltage, and a red one for high voltage.
2. The buzzer sounds off when the voltage is too low (with short beeps) or too high (with a continuous sound).

Designing and printing the Printed Circuit Board (PCB) came next after the schematic diagram was complete.

ExpressPCB was used to design the PCB. To guarantee correct alignment and spacing, the parts from the schematic layout were carefully positioned and routed on the board. Built-in design rule checks (DRC) were used to verify that the layout complied with the necessary mechanical and electrical requirements. The Gerber files were created and ready for production once the design was complete.

The PCB was manufactured utilising the toner transfer method, which involved using a laser printer to print the PCB design onto glossy paper while maintaining correct alignment for the transfer procedure. Afterward, a copper-clad PCB was ironed with the printed design. A protective layer was formed on the copper by the toner being transmitted by the iron's heat. The surplus copper was finally removed from the PCB by etching it in a ferric chloride solution, leaving only the traces that the toner had covered.

Soldering the parts and completing the board for use in the ElectraGuard came next once the PCB had been manufactured and etched.

To avoid any residues, oils, or dust that can interfere with the soldering process, the PCB was cleaned. To guarantee a clean surface, alcohol or a fine abrasive pad were utilised. Then, in accordance with the design, every component including resistors, capacitors, ICs, LEDs, and the relay—was meticulously positioned in its proper location on the PCB before being soldered to it. Careful soldering was used to prevent solder bridges between neighbouring pins and guarantee solid, clean connections. For accuracy, a soldering iron and fine solder were utilised.

After every component was soldered, the connections were examined visually to make sure there were no bad connections or short circuits and that every part was firmly fastened. To check for continuity and make sure there were no shorts and all the wires were connected correctly, a multimeter was utilised.

Following soldering, isopropyl alcohol or a specialist PCB cleaning solution was used to clean the PCB once more to get rid of any flux residues.

Once the PCB was assembled and finalized, the next step was to design and 3D print the enclosure for the ElectraGuard to ensure the protection of the components and ensure that the system is safe, durable, and aesthetically pleasing.

The enclosure was designed using SketchUp and was sized to fit the completed PCB, ensuring there was enough space for all components, wiring, and ventilation. Also, the slots for the power input, relay, LEDs, buzzer, and other connections were planned in the design. The design also considered ease of access, cable management, and a clean, professional look. After completing the model, the design was exported as an STL file, which is compatible with 3D printers.

The enclosure was printed using the BambooLabs 3D printer. This printer allowed for precise printing with high-quality material, ensuring a strong and accurate result. PLA filament was used for the print, chosen for its ease of use, durability, and finish. The 3D printer followed the design specifications, layering the material to form the exact shape of the enclosure. The design was printed in separate parts (top and bottom sections) to facilitate easier assembly and ensure structural integrity.

After designing and 3D printing the enclosure, the final step was to assemble the system and ensure everything was securely put together and functioning as intended. This step involved mounting the PCB inside the enclosure, connecting the necessary wiring, and ensuring all parts fit perfectly.

The completed PCB was carefully inserted into the enclosure, making sure that every part (including the power input, relay, and LEDs) lined up with the appropriate apertures. After that, wiring was passed through the appropriate holes, making sure that every connection was safe, tidy, and devoid of any chance of short circuits. The enclosure was examined to make sure the PCB fit securely, that there was no chance of parts hitting the enclosure walls, and that there was adequate room for the cables. Lastly, the design was reviewed again to ensure that key parts such as the relay, power input, and indicators were accessible.

The ElectraGuard was successfully completed and fully operational, offering a reliable solution for protecting electrical equipment from damaging voltage fluctuations.

Specifications:

1. Input Voltage: 230V AC (+6%)
2. Output Voltage: 230V AC (+6%)
3. Voltage Thresholds:
4. Low Voltage: Below 216.2V
5. High Voltage: Above 243.8V
6. Indicators:
7. Green LED: Normal voltage
8. Amber LED: Low voltage
9. Red LED: High voltage
10. Alarm: Buzzer for high and low voltage conditions
11. Delay: 10-second restoring delay

Key Features of the High and Low Voltage Cut Off Circuit

1. Real-Time Monitoring: Provides continuous oversight of voltage levels, ensuring immediate response to unsafe conditions.
2. Automatic Cut Off and Reconnection: Safeguards your devices by cutting off power during anomalies and restoring it when normal conditions resume.
3. Delay Functionality: Filters out transient disturbances, preventing unnecessary shutdowns.
4. Auditory and Visual Alerts: A buzzer and LED indicators provide instant feedback, informing users of current voltage status.
5. Cost-Effective: Unlike other solutions, this system uses easily replaceable components, making it budget-friendly

Real-World Applications

1. Residential: Protects home appliances like refrigerators, air conditioners, and entertainment systems from voltage irregularities.
2. Commercial: Ensures the stable operation of sensitive office equipment and IT infrastructure.
3. Industrial: Shields heavy machinery and production lines from sudden voltage surges or drops.
4. Data Centers: Maintains the integrity of critical servers and network equipment by preventing voltage-related disruptions.

What Makes This System Unique?

This design, in contrast to many commercially manufactured voltage protectors, uses common, readily interchangeable parts, such as NE555 timers and basic ICs (integrated circuits) for logic functions. Because of this, it's both affordable and easy to use. The lack of programmable chips guarantees a simple design that both professionals and enthusiasts can understand, fix, or alter with ease.

Furthermore, this system stands out due to the delay timer, which adds a level of sophistication that is frequently absent from other systems. This function strikes the ideal mix between convenience and protection by minimising disturbances while maintaining safety.

DIY Installation and Maintenance Tips

The accessibility of this voltage cut-off equipment is among its most appealing characteristics. If you have a basic understanding of electrical wiring, you can easily set up the system even if you are not an electronics specialist.

1. Follow Safety Protocols: Always disconnect the power source before installation or maintenance. Safety first!
2. Placement Matters: Install the system close to the main power supply for effective monitoring and quick response.
3. Test Regularly: Periodically test the alarm and indicators to ensure they are functioning correctly.
4. Use Quality Components: Invest in high-quality relays, voltage sensors, and other components for long-lasting performance.

The objective of the ElectraGuard project, which was to reliably protect electrical equipment from hazardous voltage fluctuations, was accomplished. We produced an effective, economical solution that guarantees gadgets are protected from both high and low voltage conditions by meticulously planning and putting the system together. It is easy to use and efficient in practical applications because it combines a delay timer, visible indications (LEDs), and an audio warning system to deliver clear and instantaneous feedback.

This project illustrated how easily accessible tools such as ExpressPCB for PCB design and the toner transfer process for printing may be combined to create a low-cost, long-lasting solution. The system is a useful addition to households, workplaces, and industrial settings since it provides piece of mind by guaranteeing the lifetime and safety of sensitive electronics after it has been successfully tested and put into use.

It makes sense to shield electrical gadgets from erratic voltage swings in a time when they are more important than ever. A dependable and reasonably priced solution that guarantees safety, extends the life of equipment, and maintains uninterrupted operations is a High and Low Voltage Cut Off with Delay and Alarm. Investing in a voltage protection system is an investment in peace of mind, regardless of whether you are an industrial operator, business owner, or homeowner.

Therefore, this system can be just what you need if you respect your electronics and want to protect them from the unpredictability of power supply changes. Keep yourself safe and secure!