In the world of DIY electronics, protecting your projects from voltage spikes is an essential task. Overvoltage conditions can damage sensitive components, causing irreparable harm or reducing their lifespan. One effective and simple way to protect your circuit is by using a Transient Voltage Suppression (TVS) diode, and in this project, we will use the SMCJ24CA TVS diode to design a basic overvoltage protection circuit.

 

Overview of the SMCJ24CA

The SMCJ24CA is a bidirectional Transient Voltage Suppression (TVS) diode designed to protect electronic circuits from voltage spikes caused by electrical transients, such as lightning strikes, electrostatic discharge (ESD), or power line cross events. This diode is rated for a clamping voltage of 24V and can handle surge currents up to 400A, making it a reliable solution for overvoltage protection.

The bidirectional nature of the SMCJ24CA means it is ideal for circuits that experience both positive and negative voltage spikes, such as signal lines or communication circuits. The diode's ability to clamp high-voltage spikes and return to its normal state after the transient has passed ensures that your sensitive components remain safe from damage.

In this project, we will integrate the SMCJ24CA into a simple circuit to protect a power supply and associated components from overvoltage conditions.

 

Components Needed

For this DIY project, you will need the following components:

1. SMCJ24CA TVS Diode – The main component for overvoltage protection.

2. Resistor – 10Ω, used for current limiting.

3. Capacitor – 100nF ceramic capacitor for filtering high-frequency noise.

4. Power Supply – 12V DC regulated power supply (or similar).

5. Breadboard and Wires – For prototyping and testing the circuit.

6. Multimeter – For measuring the voltage and ensuring proper functionality.

 

Step 1: Understanding the Role of the SMCJ24CA

Before we begin assembling the circuit, it's important to understand how the SMCJ24CA works. When a voltage spike exceeds the clamping voltage of 24V, the TVS diode will begin to conduct, diverting the excessive current away from the protected components. This helps to prevent damage from voltage transients. Once the voltage returns to normal levels, the diode stops conducting, and the circuit operates as usual.

The SMCJ24CA can absorb significant amounts of energy, but it is not designed for continuous overvoltage conditions. It is intended to protect against short-duration voltage spikes, not sustained high-voltage scenarios. That’s why we also incorporate other components like resistors and capacitors in our design to ensure the circuit’s stability and performance.

 

Step 2: Circuit Design

The basic design of the overvoltage protection circuit using the SMCJ24CA involves connecting the diode in parallel with the power supply input. The circuit is very straightforward:

● Resistor: Place a 10Ω resistor in series with the power supply input. This resistor helps limit the current flowing into the circuit when the TVS diode activates, ensuring that the diode isn't subjected to excessive current.

● Capacitor: Add a 100nF ceramic capacitor across the power input terminals to filter out any high-frequency noise that might be present on the supply line. This capacitor helps to stabilize the voltage and prevents false triggering of the TVS diode.

● SMCJ24CA: Connect the SMCJ24CA in parallel with the power supply input terminals, ensuring the cathode is connected to the positive rail and the anode to the negative rail (in a bidirectional configuration).

The final circuit is simple but effective at protecting sensitive components from voltage spikes.

 

Step 3: Building the Circuit

1. Prepare the Breadboard: Begin by placing the power supply lines (positive and negative) onto the breadboard.

2. Connect the Resistor: Place the 10Ω resistor between the positive power rail and the input of the circuit. This will limit the current when the SMCJ24CA is activated during an overvoltage condition.

3. Place the Capacitor: Attach the 100nF ceramic capacitor across the power supply input terminals. This will help smooth out any high-frequency fluctuations in the power supply, ensuring that the TVS diode only triggers in the event of a legitimate overvoltage spike.

4. Install the SMCJ24CA Diode: Finally, insert the SMCJ24CA diode in parallel with the input, with its anode connected to the negative rail and its cathode connected to the positive rail.

Once all components are in place, double-check the connections to ensure everything is correct.

 

Step 4: Testing the Circuit

To test the overvoltage protection circuit, you can simulate a voltage spike using a variable power supply or by using a high-voltage test equipment. Set the input voltage to a normal operating level (12V, for instance), and then gradually increase the voltage to simulate a transient.

1. Normal Operation: When the input voltage is within the normal operating range (around 12V), the SMCJ24CA will not conduct. The power will pass through the circuit as usual, with the diode in a non-conducting state.

2. Overvoltage Condition: As the input voltage exceeds the diode's clamping voltage (around 24V), the SMCJ24CA will begin to conduct, diverting the excess current away from the rest of the circuit. This will protect your components from the harmful effects of the voltage spike.

3. Return to Normal: Once the transient has passed and the voltage drops back below the clamping threshold, the diode will stop conducting, and the circuit will return to normal operation.

Using a multimeter, you can monitor the voltage across the input terminals and observe the SMCJ24CA's behavior as the voltage fluctuates.

 

Step 5: Troubleshooting and Final Adjustments

If the circuit does not behave as expected, consider the following troubleshooting steps:

● Check Diode Orientation: Ensure that the SMCJ24CA is correctly oriented. In the case of a bidirectional TVS diode like the SMCJ24CA, the anode should be connected to the negative terminal, and the cathode should be connected to the positive terminal. Misorientation will prevent the diode from functioning correctly.

● Verify Capacitor and Resistor Placement: Double-check that the capacitor and resistor are placed correctly in the circuit. The capacitor should be across the power supply terminals, and the resistor should be in series with the power supply input.

● Test the Power Supply: Ensure that the power supply is functioning properly and that the voltage is being applied as expected. An incorrect input voltage could lead to misleading results.

 

Step 6: Conclusion

This simple overvoltage protection circuit using the SMCJ24CA TVS diode provides a valuable safeguard for your DIY electronics projects. By adding this component to your designs, you can significantly reduce the risk of damage from voltage spikes and transients, ensuring that your projects remain safe and functional over time.

While this project is fairly basic, it demonstrates how easy it is to integrate overvoltage protection into a circuit using readily available components. The SMCJ24CA is an affordable and effective solution for protecting sensitive electronics from harmful voltage surges, making it a great addition to any DIY electronics enthusiast’s toolkit.

By understanding the function and proper integration of the SMCJ24CA TVS diode, you can expand this project into more complex designs, such as power supplies, communication circuits, or even microcontroller-based systems that require stable and protected voltage inputs. So, start experimenting with this simple overvoltage protection circuit and keep your electronics projects safe from electrical transients!