36w LED Grow Light Bar ( OLD )




About: i sell peppers and seedlings on my website http://juanitospeppers.com

I'm leaving this instructable up as informational please don't use this though.

I have a new version that uses 3w leds that is better. LINK HERE

The goal of this LED light is to be more efficient and comparable cost to t8 / t5 grow lights.


Lumens / watt: The LED chips used provide 100 lumens per watt compared to t8 (87 lm/watt) and t5(92 lm/watt).

PAR: By providing more light in the Photosynthetically active radiation range we increase efficiency. Because we are providing more light in the PAR range, we can decrease the total amount of light as we aren't wasting a bunch of yellows and greens.

Fixture cost:

The problem with many LED lights is they are expensive. Since we are DIY we can save lots of the labor / assembly / retail vs a production unit. It also turns out that many of the parts are actually pretty cheap...

Energy cost:

because our lights are 1/2 the power of 4' 2 bulb t8 and 1/3 the power of 4' 2bulb t5 user will see this on their energy bill.

Maintenance cost:

Led emitters cost about the same as a t8 / t5 bulb, but their life is 50,000+ hours, over twice the life of a t8/t5 bulb at 10,000 - 20,000 hours.

Step 1: Materials / Tools

Materials ~30$

Led stuff

1x Blue or Royal blue LED emitter 10w, 900ma (link)

3x Red LED emitter 10w, 900ma (link)

1x LED Driver 30w 900ma (link)

Fixture stuff

4' 3/4 in aluminum U channel (lowes, homedepot)(8ft cut in half is cheaper per ft)

power cable (scrap or new)

m2 screws (link)

some wire (i use wire with connectors so can swap out leds if they fail, but it's optional)(link)

some solder

some thermal paste


measuring tape


circular saw(or other saw)

soldering iron

m2 tap

1.6mm drill bit (see above link)

screw driver

Step 2: Cut / Measure / Drill Almunium

Measure aluminium 42" (or desired) length

Cut with saw

Measure space for driver / power cable on the end

measure spacing for LED emitters

Test fit

Mark holes for LED screws

Drill with 1.6mm bit

Tap the holes with m2 tap

Step 3: Attach LEDs + Driver

Put a drop of thermal paste on led bottom

Screw it in hand tight

i'm lazy so i just taped the driver, drill holes and screw it in if you want to do the extra work.

Step 4: Wiring

Series circuit. (voltage adds). Should look like a big loop.

Solder wire (with or without connectors) between LEDs

Splice / Solder / Wrap Led>Driver

Splice / Solder / Wrap Driver>PowerCord

Step 5: Plug It In

I tested it out using peppers, onions, romaine lettuce, and zuchini, all grew just fine under it.

Remember you need 2 fixtures for a 4x2x2 area ( one led bar = one 2bulb t8 fixture).

The temperature of the fixture hovers around 60C (hottest point is at the blue led) when the room temp is 85. Runs much colder if you have a fan running near it or colder temps.

Green Design Contest

Participated in the
Green Design Contest



    • Colors of the Rainbow Contest

      Colors of the Rainbow Contest
    • 1 Hour Challenge

      1 Hour Challenge
    • Fandom Contest

      Fandom Contest

    3 Discussions


    4 years ago on Introduction

    Nice build instructions. Thank you!

    What you do you have around your growth compartment? Any additional heating?

    1 reply

    Reply 4 years ago on Introduction

    reflectix insulation... it's essentially bublewrap coated with mylar. In the winter yes it needs some heat.

    I'll be posting instructable about building the shelf sooner or later.