How to get 15v from atx power supply?

ATX power supplies are commonly used in desktop computers to provide power to various components. Typically, these power supplies offer multiple voltage outputs, such as 3.3V, 5V, and 12V, which are suitable for most computer-related tasks. However, if you have a specific requirement for a 15V power source, you might wonder how to obtain it from an ATX power supply. In this article, we will address this question and provide you with a step-by-step guide on how to derive a 15V output from an ATX power supply.

**How to Get 15V from ATX Power Supply?**

To obtain a 15V output from an ATX power supply, you can follow these steps:

  1. Ensure Safety: Before working with any electrical components, it is crucial to prioritize safety. Power off your computer and unplug the ATX power supply from the wall socket.
  2. Locate the 12V Rail: Inside the ATX power supply, identify the 12V rail. This rail is commonly denoted by a yellow wire.
  3. Identify Ground: Locate the ground connection, which is usually represented by a black wire. The ground connection will act as a reference voltage for the circuit.
  4. Calculate the Resistor Value: To step down the 12V output to 15V, you need to introduce a resistor into the circuit. The resistor value can be calculated using Ohm’s law. Assuming you want around 100mA current, a suitable resistor value would be approximately 30 ohms (R = V/I, R = 3V/0.1A).
  5. Connect the Resistor: Solder one end of the calculated resistor to the 12V rail (yellow wire connection) and the other end to the ground connection (black wire).
  6. Create a 15V Output Junction: The remaining end of the resistor will now provide a 15V output. You can connect it to a suitable terminal, such as a male/female connector, to utilize the 15V power source.
  7. Test and Verify: Before incorporating the 15V output into your project, it’s crucial to test it using a multimeter to ensure it meets your desired specifications.

Following the above steps will enable you to safely and effectively derive a 15V output from an ATX power supply. However, it’s important to note that modifying a power supply can void its warranty and should only be done by individuals with a solid understanding of electronics.


1. Can any ATX power supply provide a 15V output?

No, not all ATX power supplies have the capability to provide a 15V output. This method is applicable to ATX power supplies that offer a 12V rail.

2. What is the maximum current that can be drawn from the derived 15V output?

The current that can be drawn from the derived 15V output depends on the power rating of the ATX power supply. Ensure the load does not exceed the maximum current rating specified by the power supply.

3. Is it possible to derive other voltages using this method?

Yes, it is possible to derive other voltages by choosing an appropriate resistor value in the circuit. However, ensure that the derived output is within the power supply’s voltage limits.

4. Can I use a variable resistor to adjust the output voltage?

Using a variable resistor may allow you to fine-tune the output voltage, but it could also introduce instability. It’s generally advisable to use fixed-value resistors for consistent and reliable outputs.

5. What precautions should I take while working with ATX power supplies?

Always unplug the power supply from the wall socket before working on it. Be cautious of high voltage components and avoid short circuits. If in doubt, consult a professional.

6. What other applications can a derived 15V output be used for?

A derived 15V output from an ATX power supply can be suitable for various applications, such as electronics prototyping, audio amplifiers, and certain industrial equipment.

7. Is it possible to damage the ATX power supply during the modification process?

Yes, without proper knowledge and care, it is possible to damage the power supply or cause a short circuit. Always exercise caution when working with electrical components.

8. Can I reverse engineer the 15V output to obtain a negative voltage?

Yes, you can reverse engineer the 15V output to obtain a negative voltage by connecting the resistor between the 15V output and the ground connection.

9. Is this method the only way to obtain a 15V output from an ATX power supply?

No, there are alternative methods available to derive a 15V output, such as using a voltage regulator or a DC-DC converter. These methods may provide a more stable output but require additional components.

10. Can I connect multiple loads to the derived 15V output?

Yes, you can connect multiple loads to the derived 15V output, as long as the total current drawn does not exceed the maximum rating of the power supply.

11. Can I use a lower resistor value to obtain a higher current output?

No, using a lower resistor value will reduce the voltage drop across the resistor, resulting in a higher output voltage. It is important to choose the resistor value that suits your specific requirements.

12. Do I need to add any additional filtering components to the derived 15V output?

Depending on the project or application, you may need to add additional filtering components, such as capacitors, to minimize noise and ensure a stable 15V output.

Deriving a 15V output from an ATX power supply can be a useful skill for electronics enthusiasts and hobbyists. By following the steps outlined in this article, you can safely and confidently obtain a 15V power source for your specific project or application.

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