DIY Laboratory Power Supply Unit

A simple, microcontroller-based PWM buck converter power supply, designed to provide precise voltage control and current measurement. The output voltage is easily adjustable using a rotary encoder for accurate and intuitive input. This project is compact, affordable, and perfect for DIY laboratory power supply applications.

Features

• Voltage regulation via PWM buck converter
• User-friendly voltage adjustment using a rotary encoder
• Real-time display of voltage and current
• Custom PCB Boards
• Compact and cost-effective design (~9€)

Table of Contents

• BOM
• Assembly
• Usage
• Contributing
• License
• Schematics

Bill of Materials (BOM)

Item	Description	Quantity	Price	Total
KY-040	Rotary Encoder	1	0,89 €	0,89 €
IRLZ44N	MOSFET-Transistor (TO-220)	1	0,22 €	0,22 €
Fuse (2A)	5x20mm Glass Fuse	1	0,03 €	0,03 €
SS34	Schottky Diode	1	0,02 €	0,02 €
TM1637	4-digit 7-segment LED Display	2	1,90 €	3,80 €
DC Plug	-	1	0,24 €	0,24 €
Power Switch	-	1	0,12 €	0,12 €
TC4427	MOSFET Driver (SOP-8)	1	0,29 €	0,29 €
Buck Converter PCB	Custom PCB for Buck Converter	1	0,08 €	0,08 €
Frontend PCB (optional)	Custom PCB for Input & Displays	1	0,80 €	0,80 €
Raspberry Pi Pico	Microcontroller	1	2,00 €	2,00 €
Electrolytic Capacitor	470µF	1	0,30 €	0,30 €
Ceramic Capacitor	1µF	1	0,10 €	0,10 €
Inductor	CD75, 47UH	1	0,10 €	0,10 €
SMD Resistor	Values 51k and 10k (1206)	2	0,01 €	0,02 €
SMD Resistor	Value 0.1 Ohm (2512)	1	0,01 €	0,01 €

Total: 9,01 €

Assembly

1. Order the PCBs: For easier and cleaner assembly, it is recommended to order the PCBs from manufacturers like JLCPCB, PCBWAY, or AllPCB. Both the Buck Converter PCB and the optional Frontend PCB can be used. Just upload the appropriate Gerber files (buckdown-pcb, frontend-pcb)
2. Solder the components: Carefully solder all the required components. The project includes both SMD and THT parts, so make sure you have the right tools and technique.
3. Flash the microcontroller:

• Connect the Raspberry Pi Pico to your computer while holding the BOOTSEL button during startup.
• You can either compile the firmware yourself or simply upload the precompiled .uf2 file provided in the releases section.

4. Connect the wiring:

• Connect the Buck Converter PCB and the Frontend PCB (if used) using the following connections:

  • GND → GND

  • I+ → I_in

  • U+ → U_in

• Connect the output of the Buck Converter:

  • V_out+ → Positive output terminal (e.g., banana plug).

  • V_out- → Negative output terminal (e.g., banana plug).

You can use banana plugs, terminal blocks, or any other suitable connectors for your output.

• If using the Frontend PCB, connect both TM1637 displays and the rotary encoder to the appropriate headers.

• Make sure to add a fuse (e.g., 2A) to protect your circuit from potential damage.

• To power the Raspberry Pi Pico, you can either:

  • Power it via USB, or

  • Use a separate buck converter module (e.g., LM2596S) connected in parallel with the DC input.

Usage

To adjust the output voltage:

• Turn the rotary encoder left to decrease the selected digit.
• Turn it right to increase the selected digit.
• Press the rotary encoder to switch between digits.

You can fine-tune the PI controller parameters (K_P and K_I) experimentally in the firmware to improve voltage regulation stability and response. See RegulatorManager.hpp for details.

Contributing

Contributions are welcome! Feel free to fork this project, submit pull requests, or open issues for improvements and bug fixes.

Third-Party Libraries

This project uses the following third-party software:

• Raspberry Pi Pico SDK
  Official SDK for Raspberry Pi Pico microcontroller.
  License: BSD 3-Clause
  https://github.com/raspberrypi/pico-sdk

• TM1637_lib
  Library for controlling TM1637 7-segment displays.
  License: MIT
  https://github.com/gavinlyonsrepo/displaylib_LED_PICO

License

This project is open-source and available under the MIT License.

Schematics