DIY 310 W COB Growlight for under $350

render picture of diy grow light
SketchUp Render of the DIY COB Light

In this guide I will describe you in all detail what you need and how to manufacture a COB growlight using state of the art LED technology. 

This is instruction is perfect for growareas of 6 ft² – 9 ft² hanging at a minimum height of 45cm. 
I will also assume that you do not want to use an external potentiometer to dim the light. The light is dimmable through the driver directly.

Disclaimer: This guide is an example for one of the most efficient ways to distribute grow light in a 80cm x 80cm grow tent. If your tent has different measurements it is on you to figure out what is best for your setup. This article is more of an inspiration.

Another note: I am not an electrician. If you are not sure about your build please let a friend look through everything. Don’t die! 🙂

Item list

ItemQtylinkprice/$
Aluminium L-profile620
Aluminium flat profile16
Screw tap1amazon15
Norm screw set1amazon19
COB Modules4digikey80
MeanWell HLH-320H-2100A1100
Arctic Processor Cooler4amazon56
Thermal glue1amazon8,5
Cable1amazon15
4-way 4-pole Y-splitter1amazon9
12 V / 1A Power plug 1amazon9
Wago clamps1amazon7
total344.50

Aluminium Profiles

This will be the framing of your light. You will need 7 pieces of aluminium:

top view render of DIY grow light
Light Framing – Red: L-Profiles, Green: cuboid
  • 6 x 515 mm long L-profiles (measurements below)
  • 1 x 515 mm long cubiod (50 mm x 3 mm)
measurements of the L profile
Measurement of the L-profile

The COB Modules: Bridgelux Vero 29 SE 3500K

picture of COB module

This is your work horse. Four of these lights are enough to light up a 3×3 grow area. The BXRC-35E10K0-D-73-SE is able to put out 147 lm/W with a nice 3500k spectrum (warm white).

FAQ

  • Can I use other COBs aswell? Yes, but make sure the driver you choose fits your setup!
  • Why is this COB better than others? To compare two COBs you first look at the spectrum. This COB has a 3500 K warm white spectrum. After that you compare the effiency. Cheap COBs from amazon likely use COBs that do not reach the output levels of this light at the same power region. With this one you will only need four modules to reach 310W at this efficiency level. 

The Driver: Meanwell HLG-320H-C2100A

This is the heart of your light. The driver will power your COBs. Read more about drivers here. 
This driver is a highly efficient device which will provide you with a constant current of 2100 ma and a voltage range of 76 VDC to 152 VDC.

Thats fitting for the setup! The COBs need a voltage of 36.6 V. We got four of them and connect them in series, resulting in a total voltage of 146.4V .

Wiring schematic for a series connection

To get the same result while wiring everything in parallel you will need a driver that puts out 8.4 A and 36.6 V constant voltage.

Cooling: The Arctic Alpine 64 Plus

This CPU cooler is quiet, can dissipate up to 100 W of thermal energy and is really cheap! It is also possible to use pre drilled passive heatsinks, but these cost at least $30 each.
Disadvantage of active cooling: It can fail!

Contruction

Disclaimer: I wont provide exact measurments. Just make sure everything is perpenticular and has some kind of symmetry to it.

Drilling

First use your screw taps to build the framing. Drill holes at the the marked spots and use your screws to hold everything together. Use one of the coolers to check out the right distance between the two profiles on top and bottom, so the coolers can just be put on top of it.
Remember, that you might need some more holes for the hanging.

Attaching the driver to the middle piece and build the frame

Make sure to screw the driver very tightly to the middle piece, exactly in the middle so everything hangs in an even plane in the end. (no tilt)

example for the frame hanging
My solution to hang the light. 

After that you screw the L profiles and the middle piece with the driver togehter. Work as exact as it gets. If done right, the drivers should fit into the gaps.

Framing of the DIY COB
This was my first framing. Its not perfect, but good enough 🙂

Attach the COBs to the coolers

In the case of the Arctic cooler im recommending, there will be a layer of heatconducting paste on it. You have to remove it, before you attach the COB.

Back of arctic alpine cooler
Remove the layer of thermalpaste first

To remove the thermal paste you need to use a special alcohol solution. This one here is sufficient.

heatpaste removal
Use this or an equivalent solution to remove the thermal paste.

After that you can apply the backside of the COB with a little amount of thermal glue. 

IMPORTANT: MAKE SURE THE HEATPASTE IS ACTUALLY A GLUE WITH HEAT CONDUCTING PROPERTIES. THIS BUILD DOESNT USE SCREWS. IF YOU USE THE WRONG KIND OF PASTE, THE COB WITH JUST FALL OF AND WILL BREAK FROM HEAT DAMAGE! THIS IS A FIRE HAZARD!

Heat paste on COB module
This is a good amount of thermal glue. Let it spread by pressing it on the cooler.

You do not need to spread the thermal glue manually. Just press it on the cooler and let it distribute by pressure.

Wiring and testing the lights

Wago clamps
Use the Wago clamps to connect cables.

Place the COBs attached to the cooler on the framing to determine the amount of cable you need. After that you can start cutting the right amount of cable and wire it to the COBs. Please watch this video if you are not sure how to wire a COB.  Remeber: You use serial wiring.
You now have to attach the input cable to the driver. Just cut open a cold device cable. Make sure you work according to the color coding of the wires. If you fuck up here it can be dangerous! Use the Wago clamps to connect everything.
If you think you have done everything right please DOUBLE CHECK everything.

Attach this to your driver. This is an EU cable!

You can now test the COBs for 5 seconds max. This is important, because the active cooling is not connected yet. Cover your eyes, this is going to be bright! (Im serious here!) 

Power up the cooling

Now that the light works, the last step is to connect the cooling to the power. This is why you have to buy a 4-Way Y-connector. This is used to wire all the fans on the coolers together. Then you just connect the remaining wire to a sufficient power source (12 V, 1 A) and you are done. The cable from the Y-connector has four wires and are color coded as shown here. You only need 12VDC and GND to run the fans. If you are clever you make use of the PWM cable as well to lower the rotation speed if needed.

COB light in a growtent
The DIY COB Light in action!

Have fun growing!

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6 thoughts on “DIY 310 W COB Growlight for under $350”

  1. Hello!
    Thank you for awsome DIY guide!
    I have some questions for you:
    – what is your overall impression of lamp functionallity
    – is it correspond a 250W or much potent HPS lamp
    – do you use it for all fases (veg./grow)
    – why you didn’t incluide in construction an UF/infrared leds
    – what is working temperature inside your box with this lamp

    Thanks in advise

    1. Lamp worked well, until I got it replaced. I gave my build away already. It should run way more efficient than a HPS. Spectrumwise theyre not really comparable, since HPS have alot more red going. My light is a seed->harvest light. No need for a veg/flower mode with 3500K LEDs. Its a compromise though. I didnt know how to add some UV/IR LEDs to the build. This build is extremely simple bc its just based on parallel connection. The lamp runs very cool due to the active cooling. With proper air cycle youll see 25°C with the lights on in a 3×3.

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