How to convert an ATX (desktop computer) PSU into a bench power supply

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An illustration of a woman in an electronics lab.

When working on ESPHome projects using an ESP8266, ESP32, or RP2040, a stable and suitable power supply is a must. While you may use a single power source for your final project, a bench power supply can be a game-changer during the prototyping phase. However, these devices can be expensive and cumbersome. But fear not, a dusty old ATX computer power supply might just be the answer to your power supply needs.

An ATX power supply usually used in a computer has been converted to a bench power supply
An ATX power supply, such as this one from Corsair, makes for a perfect bench PSU

The advantages of ATX power supplies for ESP projects

ATX power supplies are a great option for ESP32, ESP8266, and RP2040 projects for several reasons: They are affordable, especially in the second-hand market, they provide ample power, a fan to keeps it from overheating, and, if bought wisely, they have all the required safety features, protecting you and your components. The last point is not to be overlooked, as the use of an ATX computer power supply keeps any live wires hidden away, exposing you only to low voltage currents. Most importantly, they provide clean and stable 3.3V, 5V, and 12V outputs – exactly what your ESPHome projects require – without any additional fuss.

A sticker on an ATX power supply displaying the various output voltages and maximum amps.
A sticker on an ATX PSU displaying the output voltages

Understanding the 24-pin ATX power supply connector

The key to turning an ATX power supply into a bench power supply lies in the 24-pin connector, which you would typically connect to a computer's motherboard. Any other cable can be disregarded, though I do not recommend removing them due to the risk of shorts.

On the 24-pin connector, different coloured wires correspond to different voltage levels: orange for +3.3V, red for +5V, and yellow for 12V. All black wires are ground connections.

Among the other coloured wires (purple, grey, brown, and green), the green wire is crucial for powering on the ATX supply.

The 24-pin connector on the ATX power supply is used for the bench power supply.
The 24-pin connector on the ATX power supply is used for the bench power supply.

Powering up your ATX power supply

You might wonder how to switch on an ATX power supply without connecting it to a motherboard. The solution is simple: create a bridge between the green wire and any black (ground) wire. Ensure that the power supply is switched off or unplugged before inserting a short wire between the two pins. Once connected, you can turn the ATX power supply on and off using the switch on the unit.

The on/off button on an ATX power supply
You can use the on/off switch on the back of the ATX power supply by bridging two pins

Opting for a more refined approach

If you prefer a neater solution, consider investing in a board, such as the XH-M229, designed to connect to the 24-pin ATX connector. These boards offer added benefits like a power indicator LED, an on/off switch, and individual connectors for different voltage levels. They also have fuses to protect your boards in case of a power surge.

You can find 3D models online to further enhance your setup by covering exposed wires. The XH-M229 is available for purchase on various online platforms, including AliExpress, for less than $3.

With just a bit of tinkering, you can transform an old ATX power supply into a cost-effective and efficient bench power supply for your ESP projects, ensuring a stable development environment without breaking the bank.

A 3D-printed case for an ATX power-supply
A 3D-printed case for the breakout PCB

Warning: risk of electrical hazards

Working with live wires can be extremely dangerous and carries the risk of electrical shock, fire, or other serious injuries. Home Assistant Guide is intended to provide general information and guidance, but it does not assume any responsibility for the accuracy, completeness, or suitability of the information provided.

It is important to note that electrical work should only be undertaken by individuals with the necessary knowledge, skills, and experience. If you are not familiar with electrical systems or unsure about the steps involved, it is strongly advised that you seek professional assistance or consult a qualified electrician.

By using the information provided in the Home Assistant Guide, you acknowledge and accept that you are solely responsible for any consequences or damages that may arise from your actions. The Home Assistant Guide cannot be held liable for any harm, injury, or damage to property resulting from your use of the information provided.

Always prioritize safety and exercise caution when working with live wires or any electrical components. It is essential to follow local electrical codes, regulations, and safety guidelines to minimize the risks associated with electrical work.

A portrait photo oif Liam Alexander Colman, the author, creator, and owner of Home Assistant Guide wearing a suit.

About Liam Alexander Colman

is an experienced Home Assistant user who has been utilizing the platform for a variety of projects over an extended period. His journey began with a Raspberry Pi, which quickly grew to three Raspberry Pis and eventually a full-fledged server. Liam's current operating system of choice is Unraid, with Home Assistant comfortably running in a Docker container.
With a deep understanding of the intricacies of Home Assistant, Liam has an impressive setup, consisting of various Zigbee devices, and seamless integrations with existing products such as his Android TV box. For those interested in learning more about Liam's experience with Home Assistant, he shares his insights on how he first started using the platform and his subsequent journey.

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