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Build an LED COB Grow Light

Dina Soto
Build an LED COB Grow Light

Building your own LED grow light has numerous advantages, from cost savings to customization to increased efficiency. Creating your own light can be a fun project and will result in a final product that is more powerful and efficient than pre-made units available on the market.

The Easy Way

Let's start with a common build for this tutorial: 4x 36 volt COBs on a Mean Well HLG-185H-C1400. This setup provides approximately 50 watts per COB, totaling 200W. With this configuration, the light will cover a space of about 2.5'x2.5' for flowering plants and up to 3'x3' for vegetative growth or leafy greens. For this tutorial, I received the components from Horticulture Lighting Group, and I want to express my gratitude to them for supporting the DIY community. Be sure to check out their Quantum Boards!

Of course, you have the freedom to choose your own components for your system. If you decide to explore other options, I recommend reading our post on Selecting COB LEDs and Matching Drivers, and check out our constant current driver selection tool that allows you to easily design your system using popular COBs and Mean Well HLG series drivers.


Here is the list of parts for this build:

  • 4x Citizen CLU048-1212 Gen. 6 COBs
  • 4x IDEAL 50-2204-CT COB Holders
  • 4x 120mm Pin-Fin Heat Sinks (suitable for up to 60 watts, larger heat sinks needed for higher power)
  • 8x M3 Screws to attach COB holders to heat sinks
  • 1x Mean Well HLG-185H-C1400B LED Driver
  • 1x Thermaltake Thermal Grease - TG4
  • 2x Wago 2 Conductor Connectors
  • 1x 100K Ohm Potentiometer
  • 1x LLT-L20 Waterproof Power Connector with Power Cord
  • Red and black 18 Gauge Wire

Read more: What is a Good Light Fixture for a Kitchen?


The following tools are required for this build:

  • Wire Strippers
  • Screwdriver
  • Soldering Iron
  • Old Plastic Card for spreading thermal grease


1. Installing the COBs in COB Holders

The first step is easy. Take a COB and fit it into one of the COB holders. Depress the springy tab and fit the COB into the corners. The back of the holder should have a plus symbol to indicate the positive side of the COB. Match this symbol with the one on the front of the COB.

2. Applying Thermal Compound to the Back of the COB

There are different methods for applying thermal compound. You can use thermal compound or purchase thermal pads that are sized for your specific COB. If you choose thermal compound, apply a pea-sized amount to the back of the COB and spread it evenly with an old plastic card.

3. Fastening the COB & Holder to the Heat Sink

If you have the right heat sinks for your COBs, they should come with pre-drilled holes that match the mounting points of the holders. Line up the holder and ensure that the screw holes align to fasten it down. Also, check if the screw holes for attaching a reflector line up.

4. Terminating Your LED Driver AC Connection

If you are unfamiliar with working with electricity, seek assistance for the driver terminations. Ensure everything is unplugged until you are completely finished and confident that all wiring is correct.

Consult your driver's manual or check the printing on the driver's case for information on wiring the AC connection. Tighten the connections securely and make sure no stray strands of copper are exposed. Terminate the driver into one side of the connector and attach the power cord to the other side, matching the wire colors according to the driver's instructions.

5. Terminating Your LED Driver DC Connection

The same safety precautions apply to the DC side of the driver. Ensure all connections are double-checked before powering on.

Most people use Wago connectors for the DC side. Strip back the driver output wires and insert them into separate Wagos. Connect the positive side of the COB run to the positive Wago and the negative side to the negative Wago for a series connection.

6. Terminating Your Dimming Potentiometer ("B" Style Drivers Only)

If you have a Mean Well driver ending in "B" (e.g., HLG-185-C1400B), you must terminate an external potentiometer to dim the light. If you have the "A" version of the driver, it will come with a built-in screw terminal for dimming. Follow the instructions for terminating the potentiometer on a B type driver.

7. Building a Frame

Watch the provided video for step-by-step instructions on building the frame for the 4 Citizen COBs.

8. Connecting the COBs to the Driver

Stay tuned for information on connecting the COBs to the driver. In the meantime, check out our post on wiring in series and parallel.

Read more: How Are LEDs Made?

The Hard Way

If you prefer not to use a pre-drilled heat sink, you can make your own using a CPU cooler. Here's how:


The required components for this build are as follows:

  • 1x Bridgelux Vero 18 (BXRC-50E4001-C-74) with Wire Harness
  • 1x Mean Well LPC-60-1400 LED Driver
  • 1x ARCTIC Alpine 64 Pro Rev. 2 CPU Cooler (Ensure the CPU cooler has enough surface area for your COB)
  • 1x Thermaltake Thermal Grease - TG4
  • 1x 10 Pack of Ideal 30-1034J In-Sure Push-In Wire Connectors (Alternatively, use Wago connectors)
  • 1x 12V 300mA Power Supply for the CPU Fan
  • 1x Cheap Extension Cord


For this build, you will need the following tools:

  • Cordless Drill with Drill Bits
  • Digital Multimeter
  • Wire Strippers
  • Sharpie
  • Grinding Bit
  • Plastic Card for spreading thermal grease

Read more: How to Convert Recessed Lights to LED


There are three main steps to assembly: attaching the COB to the heat sink, wiring the LED driver, and wiring the fan.

1. Attaching the COB to the Heat Sink

This step requires patience and precision. Remove the thermal grease provided with the CPU coolers and wipe it off with a paper towel. Mock up the COB on the heat sink, mark the screw holes with a Sharpie, and detach the fan for easier drilling.

Drill the holes precisely, and if necessary, grind off any burrs to ensure the COB sits flat. Apply a thin layer of thermal paste to the back of the COB and spread it evenly with a plastic card. Screw the COB into place, alternating between screws for even pressure.

2. Wiring the LED Driver

Wiring the COB to the driver is straightforward, especially if you can avoid soldering. Use a wire harness for the COB. Connect the wire harness to the COB, and then connect the other end to the driver using push-in connectors. It is recommended to use Wago connectors instead of push-in connectors for a better experience.

3. Wiring the Fan

Identify the +12V and ground wires on the CPU fan. Cut off the connector and strip the wires. Use crimp connectors or solder and heat shrink the splices. Identify the +12V and ground conductors on your power supply and connect them to the corresponding wires of the fan. Ensure all connections are secure.

The Finished Product

Once completed, you have your own DIY LED grow light. Mount it in a suitable location and start growing. The CPU coolers effectively dissipate heat, keeping the COBs cool. Remember to follow safety precautions when working with electrical components.

If you decide to embark on your own LED grow light project, please share your experience and any modifications you made in the comments section below.

Frequently Asked Questions

  1. Can I customize the components for my DIY LED grow light?
  • Absolutely! You have the freedom to choose your own components, but ensure they are compatible with each other and suitable for your desired lighting setup.
  1. What are the benefits of building my own LED grow light?
  • Building your own LED grow light allows for cost savings, customization, and increased efficiency compared to pre-made units. You can tailor the light to meet your specific needs and grow healthier plants.
  1. Is it difficult to build an LED grow light?
  • While it may seem daunting at first, building an LED grow light can be a fun and rewarding project. With the right guidance and tools, it becomes a manageable task. Just ensure you follow safety precautions and carefully follow instructions.
  1. Can I dim the light on my DIY LED grow light?
  • If you choose a Mean Well driver ending in "B", you can terminate an external potentiometer to dim the light. Alternatively, a driver ending in "A" will have a built-in screw terminal for dimming. Ensure you select the appropriate driver for your dimming needs.
  1. What size of space can my DIY LED grow light cover?
  • The size of the space your DIY LED grow light can cover depends on the wattage and configuration of the COBs used. For example, a setup with 4x 36 volt COBs on a Mean Well HLG-185H-C1400 can cover a space of about 2.5'x2.5' for flowering plants and up to 3'x3' for vegetative growth or leafy greens.

Dina Soto
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