DIY: Convert Your ATX Power Supply To A Lab Power Supply

by Tom Lembong 57 views
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Hey guys! Ever wanted a reliable and adjustable power supply for your electronics projects but didn't want to shell out a ton of cash? Well, you're in luck! Today, we're diving into the awesome world of converting a standard computer ATX power supply into a super handy lab power supply. This is a fantastic project for anyone dabbling in electronics, building circuits, or just tinkering with gadgets. Not only is it a budget-friendly option, but it's also a great way to recycle those old computer parts gathering dust in your closet. You can learn a lot about how these power supplies work. Let's get started!

Why Convert an ATX Power Supply?

So, why bother converting an ATX power supply in the first place? Well, the main reason is cost-effectiveness. Commercial lab power supplies can be pretty expensive, often costing upwards of $100 or even more, especially for those with adjustable voltage and current capabilities. However, a used ATX power supply from an old computer typically costs around $20 - $30. This makes it a super affordable alternative, especially if you're just starting out and don't want to invest a fortune. Another great reason is the learning experience. Taking apart an ATX power supply and understanding its inner workings is a fantastic way to learn about electronics. You'll get to see how different components work together, how voltage regulation is achieved, and gain a deeper understanding of power supply design. It's a hands-on way to learn and build your knowledge. Furthermore, it's also a practical solution. ATX power supplies offer multiple voltage rails (like +3.3V, +5V, +12V, and sometimes -12V) that can be incredibly useful for powering various electronics projects. They're already designed to provide stable and reliable power, which is exactly what you need for your workbench. In summary, it's a budget-friendly, educational, and practical solution for anyone looking for a versatile power source. Let's get into the specifics of what you will need for this project and the conversion steps.

What You'll Need

Before you jump into the conversion process, let's gather all the necessary tools and components. You donā€™t need a ton of stuff, which makes this project even more appealing. Here's a list of essentials:

  • ATX Power Supply: Obviously, this is the star of the show! You can typically find these in old computers, at computer repair shops, or online for a few bucks. Make sure it's in good working condition. Check the power rating to determine the maximum current you can draw from each rail.
  • Multimeter: A multimeter is essential for measuring voltages, testing continuity, and ensuring everything is working as it should. You'll use it throughout the conversion process and to verify the output voltages.
  • Soldering Iron and Solder: You'll need these to attach wires and components. Make sure you have a fine-tipped soldering iron for precise work.
  • Wire Strippers/Cutters: These are crucial for preparing the wires. Make sure you have a good quality pair to prevent damaging the wires.
  • Heat Shrink Tubing: This is used to insulate the connections and prevent short circuits. It's a lifesaver for making your project safe and tidy.
  • Banana Plug Connectors and Binding Posts: These will be used to create the output terminals. Banana plugs are the standard for lab power supplies.
  • Optional - Voltage/Current Display: A small digital display to show voltage and current can significantly enhance the usability of your new lab power supply. It adds a professional touch and makes it easier to monitor the power output.
  • Resistors (10 Ohm, 10W): You'll need these to provide a minimum load on the +5V and +12V rails to ensure stable operation. Some ATX power supplies require a minimum load to function properly.
  • A Case (Optional): While not strictly necessary, a case will protect the components and make your power supply look more professional. You can use an old computer case, a project box, or even build your own.
  • A Switch (Optional): A power switch can be a convenient addition to turn the power supply on and off without unplugging it.
  • Screwdrivers: You'll need a set of screwdrivers to disassemble the ATX power supply and attach the components. Make sure you have the correct sizes.

Step-by-Step Conversion Guide

Alright, now for the fun part! Here's a detailed guide on how to convert your ATX power supply into a lab power supply. Please note that working with electricity can be dangerous. Always unplug the power supply before working on it, and take extra care to avoid short circuits. Safety first!

Step 1: Safety First! Disassembly and Preparation

  • Unplug the Power Supply: This is the most important step! Always unplug the power supply from the wall outlet and ensure it is not connected to any other devices.
  • Open the Case: Unscrew the case and remove the top cover. Be careful of any internal components, and try not to touch anything inside until you're sure the capacitors are discharged. Capacitors can store a dangerous amount of energy even after the power supply is unplugged.
  • Discharge the Capacitors: To safely discharge the capacitors, use a screwdriver with an insulated handle to carefully short the large capacitors. Touch both terminals of the capacitor with the screwdriver. You may see a small spark, which indicates that the capacitor is discharging. Always be extremely cautious when working near capacitors.
  • Identify the Wires: Familiarize yourself with the different wires coming out of the power supply. The most important ones are:
    • +3.3V (Orange): Provides 3.3 volts of power.
    • +5V (Red): Provides 5 volts of power.
    • +12V (Yellow): Provides 12 volts of power.
    • -12V (Blue): Provides -12 volts of power.
    • Ground (Black): The common ground reference.
    • PS_ON (Green): This wire needs to be connected to ground to turn on the power supply.
    • Power Good (Gray): This wire can be left unconnected. It provides a signal to the motherboard indicating the power supply is working.

Step 2: Powering On the Power Supply

  • Locate the PS_ON Wire: Find the green wire on the ATX connector. This wire tells the power supply to turn on. It needs to be connected to ground (a black wire) to activate the power supply.
  • Short the PS_ON Wire to Ground: You can do this by connecting the green wire to any black wire using a wire connector or soldering them together. This will effectively turn on the power supply.
  • Test the Power Supply: Plug the power supply into the wall outlet (be careful!), and use your multimeter to check the voltage on the various rails (+3.3V, +5V, +12V). If the voltages are correct, your power supply is working! If not, double-check your connections and the power supply.

Step 3: Providing a Minimum Load (Important for Stability)

  • Why a Minimum Load? Many ATX power supplies need a small load on the +5V and +12V rails to function correctly. Without a load, the voltages may be unstable or the power supply may not turn on at all.
  • Adding Resistors: Solder a 10 Ohm, 10W resistor across the +5V and ground wires, and another one across the +12V and ground wires. These resistors will draw a small amount of current, simulating a load.
  • Placement: You can place the resistors inside the case, ensuring they don't touch any other components. Make sure the resistors are properly insulated to prevent any accidental short circuits.

Step 4: Connecting the Output Terminals

  • Prepare the Wires: Strip the insulation from the ends of the wires you plan to use for the output terminals (+3.3V, +5V, +12V, -12V, and ground). Ensure the wires are securely stripped to avoid any loose connections.
  • Attach Banana Plugs or Binding Posts: Connect the prepared wires to the banana plug connectors or binding posts. It's recommended to use different colors for each voltage rail to avoid confusion. For example, red for +5V, yellow for +12V, black for ground, etc.
  • Secure the Connections: Use solder or wire connectors to securely attach the wires to the banana plugs or binding posts. Make sure the connections are solid and won't come loose.

Step 5: Optional - Installing a Voltage/Current Display (For Enhanced Functionality)

  • Choosing a Display: Select a digital voltage and current display suitable for your needs. There are many options available online.
  • Wiring the Display: Follow the instructions provided with your display to connect it to the power supply. This typically involves connecting the display to the +5V and ground wires for power, and tapping into the voltage rails and ground for voltage monitoring. The current monitoring usually requires you to connect the load in series.
  • Mount the Display: Mount the display in the case or project box using screws or adhesive. Make sure it's easily visible and accessible.

Step 6: Finishing Up and Testing

  • Assemble the Case (If Applicable): If you're using a case or project box, carefully reassemble it, making sure all the components are securely placed.
  • Double-Check All Connections: Before plugging the power supply back into the wall, double-check all connections, especially the output terminals and any wiring you have modified. Make sure there are no loose wires or short circuits.
  • Initial Testing: Plug in the power supply and use your multimeter to measure the output voltages on the different rails. Make sure they match the expected values (+3.3V, +5V, +12V, -12V). Check if the voltage display is working correctly (if installed).
  • Load Testing: Connect a small load (like a resistor or a light bulb) to the output terminals and verify that the power supply can handle the load without dropping the voltage. If everything is working correctly, your converted lab power supply is ready to go!

Tips and Tricks for Success

  • Safety First: Always prioritize safety. Disconnect the power supply before working on it, and be extremely careful around capacitors.
  • Use Heat Shrink Tubing: This is a great way to insulate your connections and prevent short circuits. It looks neat and adds a professional touch.
  • Label Everything: Label the output terminals clearly. This will help you avoid confusion and prevent mistakes.
  • Choose a Well-Ventilated Case: If you are using a case, make sure it has adequate ventilation to prevent the power supply from overheating.
  • Upgrade Capacitors (Optional): If you are comfortable, you can replace the old capacitors with new ones, which can extend the life of your power supply.
  • Adjustable Voltage: For more advanced users, you can modify the power supply to have adjustable voltage output by using a potentiometer on the voltage feedback circuit. Be careful as this can be dangerous.

Conclusion

And there you have it, folks! Converting an ATX power supply to a lab power supply is a fun, affordable, and educational project that will give you a versatile power source for all your electronics endeavors. By following these steps, you can create a reliable and useful tool for your workbench. Remember to prioritize safety, take your time, and enjoy the process. Happy tinkering, and have fun building!