40W LED Grow Light

I wanted a led light that was cheap and would perform the same as or better than t8 / t5 fluorescent lights.

In this instructable i make a 50w led bar to replace a 4' 2 tube fixture

The cost is around 23$.

Step 1: Tools & Materials

Tools

soldering iron

saw

(optional multimeter for testing)

(optional 2 aa batteries for testing)

Materials 23$

18 - 21 pieces - 3w LED with star heatsink (ebay)

led driver 600mA 36-60v (ebay Constant Current Driver for 12-18pcs 3W High Power)

2 prong power cord (ebay)

thermal adhesive (ebay)

~4.50$ 42in of aluminum U channel(i bought 8' and cut in half) (lowes, home depot)

.50$ solder

1$ 8' of 20-16 gauge wire

1$ electrical tape

LED Selection:

I picked a 2 red : 1 cool white ratio.
Red has been shown to be most important and its possible to grow plants with only red light(although there are some problems). To reduce strain on the plant we give it most of the other wavelengths in small amount (from the white) and we pick cool white to give it more blue. We need about 12% blue light. With cool white being almost 50% blue light we get around 15%. I go 1 red (620nm) 1 far red(660nm) to get the most optimal light for the different photosynthesis peaks. White is easier on the eyes and provides all the other wavelengths in smaller amounts so i think its better than going just only red and blue.

Although going red and blue is possible. If you want to do that go like 5 red : 1 royal blue.

Also if you don't want to deal with wavelengths you can just go 100% white that's fine.

leds need to all be the same mA, voltage can be different.

Step 2: Schematic

Step 3: Aluminium

Cut to length (42")

remove any stickers

Step 4: Driver

attach driver to open part of u channel with some elec tape

strip / attach /solder joints between driver and power cord

cover with tape

wrap end of alum with tape to make a table on open u end.

secure cord to aluminum by making a sandwich around the cord

Step 5: LEDS

plan out the positioning..

since i have 21 leds in 42inches i did about 1.75 in spacing

put dot of thermal adhesive on bottom of led star

press firmly to aluminium

wait for adhesive to cure

i waited overnight just to be sure.

Step 6: Wire

cut wire to length and strip the ends (this takes a long time lol)

tin the terminals on the led star u will be using also tin the end of the wires

solder the wire ends to the terminals

attach to driver

measure wire from far end of string back to the driver

strip / wrap / solder

you can secure the line with tape every foot to the side of the aluminum so it's not in the way.

run line directly from driver to close end.

Step 7: Done

plug it in see if it works, if it does, yay

Step 8: =[ It Doesnt Work

doesn't light..

Get your 2 AA's tape together

put a wire on each end and put to the respective led terminals

(its ok if your hand touches this it won't shock you because so low voltages / amps)

if you find a bad led, just remove it and put a new one on there.

flashing light..

you don't have enough leds in there, you're below the minimum for the driver. (add more leds)

one of your leds is grounded to the aluminium causing a short (do the test with batteries above on each led to find the bad one)