Introduction: Flash Power Supply From Computer Power Supplies

About: I am a professional photographer with experience in design, teaching, and engineering. I spent five years teaching fundamentals of engineering to all ages, building robots, and designing classes to both infor…

The purpose of this build is to reduce a photographer/videographer's need for batteries while on a shoot. I've had issues with voltage dropoff while on photo shoots leading to me missing pivotal shots while waiting for my flashes to recharge (read more about this on my blog). While there are larger batteries and power supplies available for purchase online, they are often expensive and only run one flash at a time. This power supply build has proved to work comfortably with up to 3 of my speedlites, multiple video lights, and can be used to jump-start my car, if completely necessary- making me quite the Batterybuster.

Finally, such a build allows for more customization while utilizing a common computer part often easily available from recycling yards, computer repair stores, often found lying around the house, or just about anywhere online. This build is meant to provide help for both experienced DIYers and newcomers who want to try something new and exciting. This is my first Instructable and my entry for photography tips and tricks, if you like it or it helped you out, please vote for it!


- 2 x ATX power supplies (collected from disassembled computers)

- Plenty of large-gauge wire

- Power connectors (I used banana plugs and common ring/pole DC connectors often found on DC power supplies)

- Load resistors (I used one of these 6 ohm resistors from amazon and a 2 ohm resistor from a server donated by my father)

- High current capable switch with at least three different inputs and outputs

- On/Off switch

- 6v regulator (I found a 6v 30A on eBay)

- 9v regulator (I found a 9v 10A on eBay)

- Solder, soldering iron, solder sucker/solder wick, heat shrink, electrical tape, screwdrivers, etc.

- Multimeter

- Some sort of insulator to float a board

- A fondness for ignoring warranty stickers

All original photography copyright IH-Productions

Step 1: Prepare Your Flash

First, find a way to get your power connector to the positive and negative terminals for your power supply. You can try clipping straight onto the terminals, creating battery blanks with leads on them, or you can do what I did and drill straight through the flash body and solder your wires onto the battery terminals. If you try a method similar to what I did, ensure you have removed the batteries from the flash BEFORE hooking up the the power supply.

Step 2: Prepare Your First Power Supply: Get Your 12 Volts

Gather and combine as many of the YELLOW wires from your power supply as possible and connect them to two wires; these are your +12v wires. One of these will be used to run your 12 volts, the other will be used in combination with your second power supply for the 6 volt and 9 volt regulators (covered in step ). After that, gather and combine as many of the BLACK wires as possible (leave at least 2 for turning your PSU on, covered in the next step, and a load resistor, covered in step 4) and connect them to one wire; these are your common wires. We want as many of these wires as possible because each one individually delivers a lower current, combining them will give us as close to the current listed by the power supply as possible; this is especially important when addressing the rebound caused by the flashes charging. You can combine these cables by using ATX, sata, IDE connectors and soldering those or do as I did and just cut, strip, and solder. Make sure you insulate all your wires with heat shrink or electrical tape! If you don't, you'll get some very cool sparks! Sparks are fun, but shorting out your power supply isn't, so make your project both safe AND pretty!

Step 3: Prepare Your First Power Supply: Making It Turn On

Connect your GREEN wire to your BLACK wire; the green wire is PS_On wire and will allow your power supply to turn on when given power. Fee free to jumper them, connect them through an ATX connector, just solder them like I did. Make sure you insulate them with heat shrink or electrical tape!

Step 4: Prepare Your First Power Supply: Load Resistor

Hook up a load resistor to one RED wire and one BLACK common wire; the red wire is your 5 volts. This will allow you to get 12 volts (maybe even more) out of your power supply and help your PSU to regulate its 12 volts better when dealing with the rebound caused by your flashes charging and turning on your video lights. Without the load resistor, you'll find your PSU usually outputting closer to 10-11 volts, which isn't very useful for this build. The 2 ohm load resistor donated to me by my father came with an IDE connector, so I just plugged it in; the 6 ohm load resistors pictured came with quick splices, so I just used those. Load resistors tend to get HOT, don't touch it while your PSU is running or has recently been running. If you're gonna solder, make sure to use heat shrink or electrical tape!

Step 5: Prepare Your Second Power Supply: Float the Board

Floating the board means to just disconnect the board from being grounded to the PSU case. Open your power supply and insulate the board from the PSU case; I did this by unscrewing all the board screws and slipping a cut out piece of an old binder underneath. Don't forget that there's plenty of exposed metallic surfaces on top of your PSU board which could ground to the top, so I used the thin plastic cover-holder from the same binder to insulate the top. The point of this step is to remove this power supply's DC ground, not AC; DO NOT DISCONNECT YOUR AC GROUND, IT'S NOT A GOOD IDEA! When you combine your power supplies, the DC ground of your first PSU will provide DC ground for your second PSU.

Step 6: Prepare Your Second Power Supply: Combine Them

Run one of the wires from your FIRST power supply using the combined YELLOW 12 volts wires to the combined BLACK common wires of your SECOND PSU, remember to leave a couple black wires available for a load resistor and the PS_On wire. Then, combine and connect your YELLOW 12 volts wires to another wire just like you did for the first PSU. Doing this will hook up your power supplies in series, giving you 24 volts and a total current limited by that of the lower-rated power supply. If you've discovered the -12 volts wire on your power supply, you may be tempted to try using it; DON'T DO IT! The -12 volts wire wire indeed give you a combined 24 volts, but you'll be likely to overdraw and burn out your -12 volts, which is rated for much much lower currents. For my power supplies, I used banana plugs to connect each power supply to each other to make the PSUs easy to disconnect from each other. Make sure you insulate an exposed solder with heat shrink or electrical tape!

Step 7: Prepare Your Second Power Supply: Load Resistor and Power Switch

Hook up a load resistor to your second PSU just like you did for the first PSU. Load resistors tend to get HOT, don't touch it while your PSU is running or has recently been running. After that, you need a way of turning this PSU on and off. Since the second PSU isn't properly grounded on its own, you don't exactly want it running as soon at it's plugged in. If your second PSU already has a power switch, connect your GREEN PS_On wire to your BLACK common wire and move to the next step, otherwise attach a switch to your GREEN PS_On wire and BLACK common wire. Make sure you insulate the exposed wires; no point in installing a switch just to have your wires short themselves out!

Step 8: Hook Up Your Switch

First, hook up one of your wires from the combined YELLOW 12 volts wires from the FIRST power supply, then run its respective lead directly to your power connector; I used a banana plug connector. Next, hook up your wire from the combined YELLOW 12 volts wire from the SECOND power supply to another lead of the switch. Then, jumper this terminal to a SEPARATE terminal for the switch (not its own respective lead). Make sure you use your multimeter to test continuity. The respective leads from these other two switch leads will run individually to your 9 volts regulator and 6 volts regulator. I purchased this switch here.

Step 9: Regulate Your Power

Hooking up your voltage regulators will be the same for each one. Run the wire from your switch (which now has 24 volts) to the RED wire of your voltage regulator, then combine one BLACK common wire from one regulator to the other and connect the combined common wires of the regulators to the combined BLACK common wires of the FIRST PSU. Combine your two YELLOW wires from the regulators with the 12 volts wire connected to your power connector. I did this by combining it with the outgoing 12 volts lead from the switch. Finally, combine your two remaining BLACK common wires to your power connector; these will provide the common for your entire project box. Remember to insulate all your exposed wires with heat shrink or electrical tape!

Step 10: Test It All

Honestly, you should have been testing for continuity and power as you went along, but if not do it now! There's a common superstition in making projects that if you don't test your project before putting it together, it won't work. Who knows? Maybe you're the best DIYer ever and never make a mistake, or maybe not testing things before assembling causes it to actually break; just test the thing as you go along, it's better that way! Also, it's a good idea to add a fan to your project; this can be done by either soldering wires as needed or using a fan which connects to an available PSU connector.

Step 11: Put It All in a Project Box

Put your entire project in some sort of a project box, because no one wants to look at all your wires just hanging around. Remember, if you're gonna be taking pictures/videos for clients you want to impress, so make your project box look impressive! Extra points if you add a voltmeter/ammeter and USB ports to charge yours and your client's phones! For more impressive pictures and some insight into my projects, check out my website and blog!

This is my first Instructable and my entry for photography tips and tricks, if you like it or it helped you out, please vote for it!

All original photography copyright IH-Productions

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