DIY power supply for your LED lights

A guide how to choose and transform a regular PC power supply to provide your plants with some artificial LED lighting.

When I’ve been researching all possible options for my first microgreens setup, I primarily aimed for the cheapest yet good enough solutions. That for example means I’ve bought a large plant pot tray instead of a more typical microgreens tray, simply because in my country there are only really expensive commercial products. A very similar situation appeared with finding a power supply for LED growing lights of my choice (I went for 12V LED 4 red : 1 blue strips and they work just excellent). I knew I wanted something to run a whole rack eventually, so I calculated the approximate power needed for all lights and from there searched a specific power supply. Seeing that this would cost me at least $60 gave me an idea to look for an alternative. I knew that my lights are 12V, so I needed to find a power supply with 12V output. Luckily enough, most PC power supplies have a lot of different outputs, and one of them is a Molex connector, a 4 pin used for disk drives. After that, I just browsed the internet for a bit and went with one for $20, which works flawlessly so far.

Instructions

First of all, we need to choose a correct PC power supply. You should imagine your final setup – for example, I know I want to start small, but eventually I would like this to power a whole rack with several shelves. The power consumption in specifications of my LED strip is 14.4W, we know that the voltage is 12V, and we also estimate the total length of my LED strips (12-18 meters for the rack). Now simply multiply these three numbers, leave 30 or more percent as a reserve (you want to prevent a full load of the supply) and you will get a sum of power consumption for your system, which should serve as a starting point for your PC power supply shopping.

Besides the LEDs and power supply, you will need some spare cables, a soldering equipment, electrical insulation tubes, a hot glue gun and possibly some connectors for an easier arrangement. In the end, it is all about safety, and since we are operating in an environment where your cables can get in contact with water, you want your system to be precisely insulated.

I started with cutting my LED strip to the desired length and then continued with soldering wires to it. I used one color for the positive diode and another color for the negative diode in all my cables, that way it was very clear to connect them later. Repeated this process for every strip and since I was going to connect them all in parallel, I also bought a 3-way splitter with connectors – that way I can easily disconnect a specific strip or even a whole bunch. The splitter with connectors is a 4 pin, designed for RGB strips, but my lights have only 2 pins, so I decided to use only the 2 outer ones. I soldered my strips to the connectors and used the hot glue to insulate it all.

Now if you look up a molex connector scheme, you will notice there is a yellow +12V pin out, 2 black ground ones, and a red +5V one. For our purpose, we want the yellow +12 and any of the two black ground ones. Just simply hook your positive diode input to the yellow pin out and your negative one to the ground. The setup might seem as complete now, but if you try turning the power supply on, most likely it will not run yet. That is because of a sort of security mechanism. We can again solve this with simple connection of two pin outs in ATX connector, which is a large 20 or 24 pin connector. You are looking for a green cable, then create your own small U-shaped cable and connect the green cable output with any black one. This enables the power supply to turn on, and voila, your setup should be ready to run now!

My weapon of choice
A basic 4 pin LED power connector with my modification for only 2 pins
Molex connector setup
ATX connector turn-on hack
<
>

Obviously, this is a very amateurish option and you should consider it only in certain scenarios. If possible, you should consult your setup with a professional and get components designed for this type of work. However, if you still go with my tips, be sure to double check every connection, every wire and every potential area of some problem. Stay safe and if you’re not sure with something, please discuss it with a qualified person.

Share