Building a reliable power supply is essential for any electronics project, especially when working with breadboards and microcontrollers like Arduino or ESP32. This guide walks you through a 5V/3.3V adjustable regulated power supply built using an LM317 adjustable voltage regulator. For comparison, check out this DIY 5V regulated power supply for breadboard, which uses the 7805 IC to provide a stable +5V output—perfect for powering Arduino projects.
Circuit Design Overview
Circuit Diagram
Below is the circuit diagram of 5V/3.3V regulated power supply built with adjustable voltage regulator LM317 for breadboard.
The following video demonstrates how the power supply works.
The adjustable power supply circuit operates as follows:
Input Protection and Filtering:
- The unregulated DC input passes through a 1N4001 diode for polarity protection, followed by a 500mA ferrite bead to suppress high-frequency noise.
- A 100µF capacitor filters the input voltage before it reaches the LM317 IC.
LM317 Voltage Regulator Configuration:
- The output voltage is set by a resistor network: a 240Ω resistor is connected between the output and adjustable (Adj) pins of the LM317.
- A 390Ω resistor connects the junction of the output and Adj pins to a 330Ω resistor, which is grounded.
- A switch connected to the junction between the 390Ω and 330Ω resistors toggles the output voltage.
- Switch Pressed: The junction is grounded, producing 3.3V output.
- Switch Released: The junction is ungrounded, generating a 5V output.
Output Filtering and LED Indicator:
- The output is filtered with a 1µF capacitor and a 10nF capacitor in parallel for stable operation.
- A 330Ω resistor limits current to an LED connected to the output:
- The LED lights up when the output voltage is 5V.
- The LED turns off when the output voltage is 3.3V.
Why Use an Adjustable Voltage Regulator?
Unlike fixed-voltage regulators such as the LM7805, which are excellent for providing a stable 5V output for Arduino and similar devices (learn more), adjustable regulators like the LM317 offer versatility. This circuit is particularly useful when you need multiple voltage levels for different components in your project.
For insights into designing advanced voltage regulators, explore these detailed guides:
- How to Design a Series Voltage Regulator
- Designing Series Voltage Regulators with High Precision
- Op-Amp-Based Shunt Voltage Regulator Design
- High-Output Shunt Voltage Regulator Explained
- Basic Shunt Regulator Design Made Simple
Custom Power Supply Applications
This adjustable power supply is ideal for projects requiring flexibility in voltage levels. For Arduino-specific applications, consider designing a custom power supply for Arduino that meets specific project requirements. If you're exploring series regulator designs with op-amps, check out how to design op-amp series voltage regulators for more insights.
Conclusion
This 5V/3.3V adjustable regulated power supply provides a versatile solution for breadboard projects, combining simplicity with functionality. If you primarily need a stable 5V output, the LM7805-based regulated power supply might be more suitable. For advanced designs, the linked resources provide valuable guidance on crafting precision voltage regulators.
By integrating high-quality components and leveraging versatile designs, you can create reliable power supplies tailored to your electronics projects.
