⚠️ CRITICAL SAFETY WARNING: HIGH VOLTAGE & CURRENT
- Mains Voltage Danger: This project involves 110V/220V AC. Always work with the power unplugged, and use an isolated AC-DC power brick (e.g., a 36V 5A laptop-style adapter) for the safest DIY experience.
- Short Circuit Protection: Never test the output without verifying the Constant Current (CC) limit first. A direct short at 30V/5A can melt wires and cause severe burns or fire.
- Heatsinking: The pass transistor or buck converter IC will dissipate significant heat. A properly sized aluminum heatsink with a fan is mandatory.
%20with%20ESP32%20Control%20&%20Data%20Logging.png "DIY Smart Bench Power Supply (0-30V, 5A) with ESP32 Control & Data Logging")
Welcome back to TechFix Hub! If you've built our basic LM317 adjustable power supply, you already know the joy of powering your own circuits. But as your projects grow (ESP32 clusters, motor drivers, LED arrays), you need more: higher current, precise digital control, and real-time monitoring.
Commercial bench power supplies are expensive. In this ultimate guide, we will build a Smart 0-30V, 5A Bench Power Supply using a high-efficiency buck converter module, an ESP32 for digital control, and an INA226 sensor for precision measurement. The result? A professional-grade, WiFi-connected lab tool for under $40.
⚙️ 1. System Architecture: How It Works
Unlike traditional linear power supplies that waste massive amounts of energy as heat, our design uses a hybrid approach for maximum efficiency and precision:
- The Power Stage (Buck Converter): We use a robust switching regulator (like the XL4015 or a custom synchronous buck) to step down the input voltage (e.g., 36V) efficiently. Instead of a physical potentiometer, its feedback (FB) pin is driven by a filtered PWM signal or DAC from the ESP32.
- Precision Sensing (INA226): While the ESP32 has a built-in ADC, it's not accurate enough for lab-grade measurements. The INA226 I2C sensor measures both voltage and current with 0.1% accuracy, handling up to 36V and 20A.
- The Brain (ESP32): Reads the INA226 data, drives the OLED display, manages the digital potentiometer/DAC for voltage setting, and implements software-based Constant Current (CC) and Constant Voltage (CV) protection.
- User Interface: A rotary encoder for intuitive voltage/current adjustment, and a 0.96" OLED display for real-time readouts of V, A, W, and Wh (Watt-hours).
🛠️ 2. Bill of Materials (BOM)
🔧 3. Step-by-Step Assembly Guide
- Prepare the Power Stage: Mount the XL4015 module onto a large aluminum heatsink. Apply thermal paste between the IC and the heatsink. Attach a small 5V DC fan to the heatsink, powered by the ESP32's 5V pin via a transistor switch.
- Wire the Sensing Stage: Connect the INA226 module in series with the positive output line. Ensure the "Vbus" is connected to the output, and the shunt resistor is between the input and output of the INA226. Connect SDA/SCL to ESP32 (GPIO 21 / 22).
- Implement Digital Control: To control the XL4015's voltage digitally, disconnect its onboard potentiometer. Instead, use an MCP4725 DAC (I2C) or a filtered PWM output from the ESP32 connected to the XL4015's feedback (FB) pin via a voltage divider. This allows the ESP32 to "trick" the buck converter into outputting the desired voltage.
- Assemble the UI: Wire the OLED display and the KY-040 rotary encoder to the ESP32. Use the encoder's push button to toggle between "Voltage Set" and "Current Limit" modes.
- Calibration: Before connecting any load, use a trusted multimeter to calibrate the INA226 readings in the ESP32 code. Adjust the shunt resistance value in the code until the displayed voltage and current perfectly match the multimeter.
🚀 4. The "TechFix Hub" Upgrade: Smart Lab Features
A standard power supply just outputs voltage. A smart power supply transforms your workflow. Here is how we leverage the ESP32:
- WiFi Data Logging & Graphing: The ESP32 hosts a lightweight web server. Connect to it via your phone to view real-time graphs of voltage, current, and power consumption over time. Perfect for profiling a device's startup current spike.
- Watt-Hour (Wh) Meter: The code integrates current over time to calculate total energy consumed. Use this feature to accurately measure the battery capacity of your DIY power banks or 18650 packs.
- Programmable Profiles: Save your most-used settings (e.g., "3.3V ESP32 Mode", "12V 2A Motor Mode") to the ESP32's EEPROM. Recall them instantly with a long press of the rotary encoder button.
- Advanced Protection: Implement software OVP (Over Voltage Protection) and OCP (Over Current Protection). If the current exceeds the set limit, the ESP32 instantly pulls the DAC voltage to zero, acting faster than most hardware fuses.
🔗 Complete Your Lab on TechFix Hub
This smart power supply is the heart of your workshop. Pair it with our other essential guides:
✅ Conclusion
Building a smart bench power supply is the ultimate rite of passage for any serious electronics enthusiast. By combining the raw efficiency of a switching buck converter with the precision of the INA226 and the connectivity of the ESP32, you get a tool that outperforms entry-level commercial units. It’s safe, highly accurate, and packed with smart features that will make every future DIY project easier and more professional.
🛠️ Building your own lab equipment?
Have questions about the DAC feedback loop, INA226 calibration, or ESP32 web server coding? Drop your questions in the comments below, and the TechFix Hub community will help you troubleshoot!
