Buck Converter Photography Light Hack

When I’m taking close-up photos for this blog, I regularly use my Scanlio mini photo booth.

It’s not bad for what it is – a few sides of plastic and a paper sheet through the middle. What’s really important is having loads of light beaming into it, otherwise backgrounds look grey and are difficult to edit.

For that I use a cheap 130-LED photography light from Aliexpress. It came without a power supply, ready to take a handful of AA batteries. This works fine, but they always die at the wrong time and/or the strength of the light is inconsistent.

I noticed a 9V female barrel jack connection on the rear of the light, so decided to move to mains power. I had no 9V barrel jack PSUs in my stash, so rather than buy a new one I decided to make use of a 12V PSU using a buck converter and some parts I had laying around.

Parts Used

Amongst my boxes of bits n’ bobs from over the years I found the following donors for this small project:

XL4015 5A DC-DC Step-down Buck Converter (taken from my robot arm project) – Amazon £4.95
A Huawei 12V 1A switching power adaptor (not sure what this came from, perhaps an old TV box)
In-line barrel jack power switch (Intended for a robot that never happened) – ThePiHut £3
Barrel Jack to USB cable (another robot part that never found a purpose in life) – ThePiHut £3

The main thing being re-purposed here was the PSU. I have so many old PSUs from phones, TV boxes and other devices that I no longer own. They come in really handy for electronics projects.

Never throw old PSUs away! This Huawei power supply was perfect for this hack

Changing voltages with a Buck Converter

The light wants 9V. The PSU offers 12V. That light is going to get pissed off if I try to give it 3 more volts than it was designed for!

In this situation we need to use a step-down buck converter – which lets you input a higher voltage, and output a lower voltage.

I had one already from my robot arm project to drop voltage down to 4-5V for servos. It’s the fancy type with variable output and a voltmeter on board, which is much more convenient than messing around with a multimeter.

Rated for input voltages from 4-38V – it was suitable for the job.

Use a step-down/buck converter to reduce voltages

Hooking it up

The circuit is really simple:

PSU > Step-down converter (12V IN) > Step-down converter (9V OUT) > LED Light

The PSU already had a barrel-jack fitting which would fit into the switch cable, so no hacking required there. I then needed to get a bit snippy with the remaining parts:

I chopped the USB end of the barrel jack switch cable off, to allow me to strip the wires and screw them into the IN terminals on the step-down converter.
Similarly (below) I chopped the USB end off of the longer USB barrel jack cable, stripped the wires, added a bit of heat shrink (that was too small…) and screwed them into the OUT terminal
I added a couple of cable ties to the wires through the PCB mount holes, to limit any tugging of the wires:

Zip ties are one-up from duct tape on the list of preferred bodging tools

First Run

To make sure I didn’t accidentally send 12V to the light, I kept that side unplugged and just ran the PSU into the step-down converter.

I clicked the right button to show me the output voltage, then using the potentiometer on the board I set the output voltage to exactly 9V:

These modules make it really easy to set the output voltage. Turn the potentiometer and watch the numbers on the display. Easy.

Once I was happy with the output voltage, I plugged the light in – done!

Bright, consistent light ready for my amateur photography

A Simple Solution

This wasn’t a complicated or time-consuming project, and was perhaps a bit more of a bodge than I would have liked, but I had to share it as it was a really handy hack. If you haven’t played with a buck converter yet, they’re really easy to use and great for all sorts of projects.

I’m not entirely happy with the exposed nature of this one, so I will be encasing the converter and mounting it to the side of my light box soon.

I found this really nice one on Amazon which comes with its own box, but it’s about double the price of the unit I bought previously: