In the world of electronics, one of the most common issues people face is the damaging effect of voltage spikes or surges. These surges, whether caused by lightning, power switching, or faulty electrical equipment, can easily destroy sensitive components and circuits. For those who regularly work with electronics or even for everyday household gadgets, a surge protection circuit is a great addition to ensure longevity and safety.
In this article, we’ll walk through a practical DIY project of building a surge protection circuit using the SMBJ200A. The SMBJ200A is a 200V bidirectional transient voltage suppressor (TVS) diode that protects sensitive circuits from high-voltage transients. By the end of this project, you will have a functional surge protector for your low-voltage circuits, ideal for small home automation devices, electronics workbenches, and other sensitive electronics.
Project Overview: Surge Protection Circuit
The goal of this DIY project is to design a basic surge protection circuit using the SMBJ200A to protect an electronic device from transient voltage spikes. This simple protection circuit will be connected in parallel with the device you want to protect. The SMBJ200A diode will clamp the voltage spikes to a safe level, preventing them from reaching and damaging the device.
This is an important circuit to implement for sensitive projects that involve microcontrollers, communication devices, sensors, and other delicate components that may be vulnerable to voltage surges.
Components Required
Here’s a list of the components you’ll need for this project:
● SMBJ200A TVS Diode – A 200V bidirectional transient voltage suppressor diode for clamping voltage spikes.
● Resistors – A couple of resistors for current-limiting.
● Capacitor (optional) – To help filter out high-frequency noise and stabilize voltage.
● Fuse (optional) – For additional protection against excessive current.
● Breadboard or PCB – For mounting the components.
● Jumper Wires – For making connections.
● Low-voltage device to protect – This could be a simple LED circuit, a microcontroller, or a sensor.
● Power Supply – To power the device you wish to protect.
Understanding the SMBJ200A TVS Diode
The SMBJ200A is a bidirectional TVS diode designed to provide protection against transient voltage spikes. It’s typically used in power supply lines to protect against high-voltage events that could damage sensitive components. This diode has a breakdown voltage of 200V, meaning that it begins to clamp voltages above this level, limiting the voltage that reaches the circuit.
When a voltage surge occurs, the SMBJ200A will conduct and divert the excess energy to the ground, preventing the voltage from exceeding a threshold that could cause permanent damage to sensitive components.
Step-by-Step Instructions to Build the Surge Protection Circuit
Step 1: Prepare Your Circuit
First, decide on the device or circuit that you want to protect. For simplicity, let’s assume we are building a protection circuit for a microcontroller board or a simple low-voltage device that runs on 5V or 12V. The SMBJ200A will protect the circuit from any unexpected voltage spikes, such as those caused by a power surge or static discharge.
Step 2: Connect the SMBJ200A Diode
The SMBJ200A diode will be connected in parallel to the power input of the circuit you want to protect. Its role is to clamp any voltage surges above 200V, diverting the excess energy away from the sensitive parts of the circuit.
● Anode (Negative): Connect the anode to the ground (negative terminal) of the power supply.
● Cathode (Positive): Connect the cathode to the positive power rail where the device is powered, which could be the +5V or +12V rail depending on your setup.
The diode should be placed as close as possible to the power input of the protected circuit to ensure it can act quickly to suppress any surge before it reaches the sensitive components.
Step 3: Adding Resistors for Current Limiting (Optional)
In some cases, you may want to add resistors in series with the power line leading to your circuit. The purpose of these resistors is to limit the current that flows through the TVS diode when it is triggered by a surge. These resistors will also help reduce the possibility of damage to the diode by limiting the amount of energy it needs to absorb.
For example, you can add a resistor in series with the power line to limit the surge current, ensuring that the diode only absorbs as much energy as it can handle. The value of the resistor will depend on your circuit’s design and the expected surge levels.
Step 4: Optional Capacitor for Filtering
While the SMBJ200A is designed to protect against large transients, high-frequency noise can still be a concern, especially in sensitive digital circuits. To address this, you can place a small capacitor (e.g., 0.1µF ceramic capacitor) in parallel with the diode or across the power input to filter out high-frequency spikes.
The capacitor will help smooth out any high-frequency transients that the TVS diode may not fully clamp, providing additional protection for delicate circuits like microcontrollers, sensors, or communication modules.
Step 5: Fuse for Extra Protection (Optional)
While not strictly necessary, adding a fuse in series with the power input can provide an extra layer of protection. In the event of a severe surge or fault, the fuse will blow before the surge can cause significant damage to the circuit or the diode.
Choose a fuse with a current rating slightly higher than the normal operating current of the circuit you’re protecting. This ensures that the fuse won’t blow under normal conditions but will provide protection in case of a surge or short circuit.
Step 6: Testing the Circuit
Once you’ve connected the SMBJ200A and any optional components (resistors, capacitors, fuse), it’s time to test the circuit. Use a low-voltage device such as a microcontroller, LED, or any other sensitive equipment to test the protection.
To test the surge protection, simulate a voltage spike by rapidly disconnecting and reconnecting the power supply, or by using a high-voltage pulse generator (if available). In the event of a surge, the SMBJ200A diode should clamp the voltage at 200V, protecting the circuit from any damage.
You can monitor the voltage across the protected device with an oscilloscope to verify that the voltage spikes are clamped within safe limits.
Step 7: Mounting and Final Adjustments
After testing the circuit on a breadboard and ensuring it works as expected, you can mount the components onto a PCB for a more permanent solution. If you’re using a breadboard, make sure all the connections are secure, and there’s no risk of short circuits or loose connections.
For a final test, power the device with the protection circuit in place and subject it to simulated voltage spikes (as done in Step 6). Verify that the circuit continues to function normally, and that the surge protection is effective.
Application Ideas
Home Electronics Protection: You can use this surge protection circuit for protecting home devices like small appliances, microcontrollers, or sensors that are sensitive to voltage spikes.
Power Supply Units (PSUs): Adding the surge protection to power supply lines helps safeguard the internal components of PSUs, especially in cases of unstable AC mains power.
Arduino and Raspberry Pi Projects: Many DIY electronics enthusiasts use microcontroller boards like Arduino or Raspberry Pi for various projects. Adding a surge protection circuit can ensure these devices are protected from potential damage due to power surges.
Communication Devices: Sensitive devices like Bluetooth modules, Zigbee transceivers, and Wi-Fi boards can benefit from additional surge protection when integrated into home automation or IoT systems.
Final Thoughts
The SMBJ200A TVS diode is a simple yet effective solution to protect sensitive electronic circuits from voltage spikes. By incorporating this protection into your DIY projects, you are taking a proactive step to ensure the longevity and reliability of your devices. This surge protection circuit is easy to build, inexpensive, and a must-have for anyone working with electronics.
By following the steps outlined in this article, you now have a reliable way to protect your devices from the potentially harmful effects of voltage surges. Whether you're building home automation systems, microcontroller-based projects, or any other sensitive electronic circuits, this surge protector will give you peace of mind knowing that your circuits are safe from unexpected electrical disturbances.