Avva Sai Pranav

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Personal Project · 2023

DIY Benchtop Power Supply

ATX PSU conversion with CC/CV control, fine/coarse tuning & multi-rail outputs — under $10.

400W Power capacity
~$10 Additional cost
5 Output rails
Completed DIY benchtop power supply with digital display, USB ports, adjustment knobs, and banana jack outputs
Completed benchtop power supply with V/A display, USB ports, and multi-rail banana jack outputs

Commercial benchtop power supplies with variable voltage and current limiting typically cost $50–$150 or more. This project repurposes a salvaged 400W ATX computer power supply into a fully featured lab bench supply for under $10 in additional components.

While the basic ATX conversion concept was inspired by the DroneBot Workshop tutorial, this build significantly extends the functionality by adding an XL4015-based constant current/constant voltage (CC/CV) module for a true variable output with current limiting — essential for safely powering sensitive circuits and charging batteries.

A dual fine/coarse knob system enables precision voltage and current adjustment, while a boost converter provides a 24V rail not available from standard ATX supplies. The front panel was hand-fabricated using an angle grinder and Dremel.

Problem Statement

Needed a reliable, low-cost benchtop power supply for Arduino projects, circuit prototyping, and embedded systems development without spending $100+ on commercial equipment.

  • Reuse: Salvaged ATX PSU instead of buying new bench supply
  • Variable output: Adjustable voltage with current limiting for safe testing
  • Multiple rails: Fixed 3.3V, 5V, 12V plus 24V for motors
  • Convenience: USB charging ports and real-time V/A monitoring
  • Accessibility: Functional, labeled front panel with easy output access

Methodology

Step-by-step conversion from ATX PSU to fully featured bench supply. Click a stage to jump there.

Component Selection & Planning

Selected a salvaged 400W ATX power supply as the base unit, providing native 3.3V, 5V, and 12V rails with sufficient current capacity for bench use.

  • XL4015 module: 5A CC/CV buck converter for variable output with current limiting
  • Boost converter: 24V generation from 12V rail
  • Potentiometers: Fine/coarse adjustment for V and I
  • Banana jacks: Outputs for all voltage rails
  • Digital display: Dual V/A monitoring
  • USB-A ports: Device charging

ATX Power Supply Preparation

Opened the ATX PSU and identified all output rails by wire color: Yellow (12V), Red (5V), Orange (3.3V), Black (GND), Green (PS_ON), and Purple (−5V standby). Bundled and sorted wires by voltage rail for organized connection to front panel outputs. Shorted PS_ON (green) to GND (black) to enable the supply to turn on without a motherboard connection.

Front Panel Fabrication

Hand-fabricated the front panel from the original ATX case material using an angle grinder for major cuts and a Dremel for precision cutouts.

  • Mounting holes: Digital display, USB ports, four potentiometer knobs, ten banana jack pairs
  • Design goal: Easy access to all voltage rails in compact form factor

CC/CV Module Integration

Integrated the XL4015 5A CC/CV buck converter module, fed from the 12V ATX rail, to provide a variable voltage output with adjustable current limiting. Replaced the onboard trim pots with panel-mounted potentiometers arranged in a fine/coarse configuration for precise voltage adjustment (coarse for range, fine for mV-level tuning) and separate fine/coarse current limit adjustment.

24V Boost Converter Addition

Added a boost converter module fed from the 12V rail to generate a 24V output, extending the supply's capability beyond standard ATX voltages. This rail is useful for powering 24V motors, solenoids, and industrial sensors commonly used in robotics and automation projects.

Test Setup

All output rails verified with a digital multimeter. Variable output tested across full voltage range with resistive loads. Current limiting verified by setting limit and shorting output — supply correctly enters constant current mode. USB ports tested with phone charging. Supply has been in regular use for embedded systems development since 2023.

3.3V, 5V, 12V Fixed rails
24V Boosted rail
1.25–10V+ Variable range
0–5A Current limit

Results

Achieved commercial-grade functionality at less than 10% of the cost by repurposing salvaged components and adding targeted enhancements.

Compare DIY vs Commercial comparison
Feature This DIY Build Typical Commercial (~$50–150)
Cost~$10 + salvaged ATX PSU$50 – $150+
Variable OutputYes (CC/CV)Yes
Current LimitingYes (0–5A adjustable)Yes
Fine/Coarse AdjustYes (V and I)Sometimes
Fixed Rails (3.3V, 5V, 12V)YesRarely
24V OutputYes (boost converter)Sometimes
USB Charging PortsYes (2×)Rarely
V/A DisplayYesYes
Power Capacity400WTypically 150–300W
Future Planned improvements
  • Negative rail: Add −12V for op-amp circuits
  • Overcurrent protection: Auto-shutdown on overload
  • Port covers: Banana jack caps for unused outputs
  • Front panel overlay: 3D printed cleaner design
  • Output switches: Enable/disable switches for each rail
Original Idea Credit: Base ATX conversion concept inspired by DroneBot Workshop's ATX Bench Supply Tutorial. All enhancements — including CC/CV control, fine/coarse adjustment, 24V boost rail, and front panel fabrication — are original work.

Additional Information

Demo video showing the variable voltage range and fine/coarse tuning demonstration.

Skills Technical skills demonstrated
  • Electronics: Power supply design, CC/CV regulation, boost conversion
  • Fabrication: Metal cutting, panel layout, wiring
  • Integration: Module interfacing, potentiometer wiring
  • Testing: Load testing, current limit verification