This site is the personal blog and project repository of George Farris.

If you are looking for the old Cowichan Valley Linux Users Group, check the side navigation. This site contains links to various projects that I either created or contribute to.

You will also find my Github page and Youtube channel here. Contact: cwg@cowlug.org

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DC Power Supply and Load Tester

Posted on: July 17, 2019, in All, Equipment, Small Touch Displays

This post describes my build of a new power supply and DC load tester for testing batteries and power supplies.  Kudos go to Lawrence Glaister, VE7IT who is also building one and was instrumental in the co-design of this project.

Features:

  • Dual adjustable supplies 0-24VDC at 5amps.
  • 12VDC Fixed at 5 amps.
  • 5VDC Fixed at 5 amps.
  • Dual USB power ports.
  • DC Load tester up to 20 amps (see note).
  • All supplies are isolated and change be chained together.
  • Load testor showsdisplays Time, Volts, Current and mAh.
  • Load can run for user supplied time or voltage set point.

Missing Features to be added:

  • Filter board for DC conditioning.
  • Logging of Load test for input into spreadsheet etc.

Description:

I built this supply in and old rack mount case but it could be built into anything.  Power supplies are off the shelf from our friends in China. 

The DC Load was a custom build and all schematics and code for microcontroller is available from my github page.  I will include links here as well.  Schematics are drawn in Kicad.  If you haven’t tried Kicad you should, it’s amazing and 100% freely available open source code.  I use it under Linux.

Power supplies:
The four power supplies are split into two fixed and two variable supplies, each capable of sourcing 5 amps. The two fixed supplies are set at 12 and 5 VDC.  The variable ones can realistically run from 1 volt up to 24.
 
Typical wiring for one panel is shown here:

I bought all my supplies from Banggood but I'm sure they can be had from anywhere.

The 120VAC to 24VDC supply is a: "Geekcreit® 4A To 6A 24V Switching Power Supply Board AC-DC Power Module"

The other supplies for the variable and fixed side are constant current, constant voltage supplies, where the on board potentiometers were replaced with panel mounted potentiometers. I soldered 3 pin headers to the supplies for easy mounting and replacement.


The 5VDC fixed supply is also connected to two USB A connectors on the front panel for powering and charging purposes. They run through the ammeter as well.

The wiring for the USB includes resistors that allow full current charging of supported devices.

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