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PC Power Supply Load Tester - Build Page

BOT Admin


Since doing reviews here on many different computer power supplies, I have always wanted an easy efficient way of stress testing them other than just hooking them to a system and then making them run [email protected] or something. SO.... why no build a box that will create load on a PSU instead of a PC! The advantage to this is HUGE because you can specify exactly how much load in watts you want to add rather than just guessing with just adding hardware. This way you know exactly how much the PSU can handle in a real world scenario, whether it's over or under it's ratings.

It started with a basic idea of just making a box with a bunch of load resistors attached to switches that I can just turn on and off. Each switch flipped would add 50W of load or something. Then the more I though about it, the more involved the project started to become. Yeah switches would be cool, BUT wouldn't it be even more cool if the entire thing was electronically controlled via some basic CPU?! (cough* adruino* cough* cough*).

Eventual Features:

  • Arduino Powered
  • Ability to load 1000W off the PSU's 12V rail
  • Full display for watt selection, and other purposes
  • Built in surge protection

And.... here is what it will look like:

The outside of the box. This use to be a massive 5V power supply

The guts.... explained. The three red boards are to read the information sent by the Arduino and to fire on the load resistors individually. Each card will be connected to 8 load resistors. The green wires are not ground (so sue me). they provide the power coming from the PSU and distribute it to each of the red cards.

The Arduino board. It's just chillin working on figuring out how to talk to other chips and blink LEDs.

The display for the tester will be on top of the unit. I ordered it last week so it should be here soon. Once I get it, I'll measure it and cut a hole in the top of the box so it will set in there nicely.

Let me know what you think! It's still a ways off. Most of the programming still needs to be done and I need to buy $100 worth of high powered load resistors. And some relays to turn them on.


This topic was modified 3 years ago by strudinox
Topic starter Posted : 08/09/2012 11:05 pm
BOT Admin

Okay.... looks like during the forum migration. A bunch of content on this post was deleted. REPOST TIME

The original layout was scraped because it took up too much space. Space is key because of how much room the load resistors and heatsinks took. I decided to stack them as you can see in the image below.

The three relay boards are daisy chained together and outputs are handled by a 74HC245 connected to a relay driver (ULN2803). Each of the three relay boards is capable of it's own surge and over current protection.

Each board has eight onboard relays which means it has the ability to power 8 resistors. Times 3x boards I've got the ability to switch up to 24 resistors.

Load Reisistors installed and mounted heatsinks to the bottom of the case. Cooling is provided by a 2.5A Delta fan. These resistors get HOT!

Towards the front of the case there's a home made power supply which poweres the Arduino, LCD display and other various internal components. the PSU outputs 5V, -5V (for LCD) and 12V. Current draw is pretty low so this thing should run pretty cool and quiet. I heatsinked the regulators just in case.

The underside of the lid houses the Arduino, PSU connectors, LCD display, and LED lights for relay activity. It's still at this point pretty messy but does the job quite nicely. I made a homemade shield to mount to the top of the Arduino. This consists of a 24HC595 chip I'm using to signal the relay boards (Needed more output pins anyways).

Also on the top is a radial encoder (turn dial). This is programmed to easily adjust the load watt setting. Additionally, there's a single push button used for confirming values.

Next feature is a current sensor. This is used to measure the current passing through the PSU's main power input wire, and give live efficiency calculations. These calculations are also handled by the Arduino and presented on the LCD display.

And here's a final inside shot of everything installed, connected and ready to rock and roll!

Final shot of the inside. Ugly as hell but does the job.

This post was modified 3 years ago 7 times by strudinox
Topic starter Posted : 08/11/2018 2:01 pm
BOT Admin

While it's very loud thanks to the Delta fan, it does an excellent job providing accurate load to the PSU:


Topic starter Posted : 08/11/2018 2:16 pm
James G.
New to GND-Tech

I realize this may be an old thread, but just saw the YouTube video on this.  It's the only tester I've seen that actually does a great job of actually loading a supply and is of the "diy" build. Did you ever release the schematics and arduino code for this?  Thanks and great job!

Posted : 01/04/2019 5:48 am