I see loads of tutorials on here about grow lights - some are downright terrible, others are decent, and most are a mix of the two.
Some are just some simple, 20ma lights - not enough for growing squat. Some are better, using 3W diodes, but the drive circuitry is often weak or non existent, or they don't use enough diodes to grow much of anything.
This project was born out a desire to fix that. The project consists of a 100 "real watts" LED, a constant current driver, and a laptop power supply. It should put out north of 8,000lm, using about 3A at 34V at full power. The best part? The parts cost less than $15. It's upgradeable, so if you want to use better, more expensive and more efficent cree diodes, you can. I'd also like to point out that the first picture was taken with the shop lights on - It's as bright as a hospital in the shop - and the light is so bright, in the photos it makes it look like the shop lights are off. The whiteout/purplish picture was taken with an iPhone where it's actually installed. As such, be careful when using this, It's left me seeing spots for 15 minutes.
Step 1: Components + Materials
You're going to need several things for this. Most come from eBay. I don't get any commision, I just chose the seller with the lowest price.
- 100W LED Module
- Heat Sink
- 12V computer fan
- 12V wall wart
- Assorted bits of wire
- Assorted bolts and nuts
- Laptop power supply
- CC/CV boost converter - There's two to choose from. you just need one.
Assuming you have some basic components, the whole assembly should cost around $12-15. If you don't have some of the basic components, this build should still cost less than $20. It's hard to beat the lumens for the money.
Step 2: Tools
Most of the tools are easily available. You need:
- Soldering gun
- Drill + drill bit (not pictured)
- Screw driver
Aluminum (my heat sink material) is remarkably soft. I had no problems drilling through it with a standard handheld drill.
Step 3: Attaching the Fan
THis is probably the most difficult step in a fairly heat project. In order to keep the heatsink cool, we're going to use a fan.
I then chose drill bits slightly smaller than my bolts.It's important to make sure your bolts will fit through the holes in your fan. Also, figure out which way your fan blows. We want to blow air across the fan in order to cool it.
Finally, the fan is lagged down to the heat sink via 4 bolts. I played with the arrangement of the fan, and marked the 4 spots to drill with a sharpie. I tried to avoid the fins of the heatsink where ever I could. I then drilled through, taking care to make sure the drill went in at a right angle.
While I've got the drill out, I went ahead a drilled two small vias for the wires to connect to the LED. Placement here isn't critical, but try not to hit any fins. The two larger holes were already in the heat sink, so I worked around those to mound my LED. If you don't have any, figure out a mounting technique or copy mine by drilling similar holes.
Step 4: Putting the Wires and LED In
Next, we're going to attach the LED to the heat sink. I used two bolts with washers in order to connect the LED to the heatsink. This is a good time to put a dab of thermal goop (arctic silver) between the LED and heatsink. It's not required, but highly recommended.
We'll also plumb the wires into the assembly. I used red and black as to not get confused about polarity, but the color doesn't matter.
Make sure to use a reasonable gauge, as it needs to potentially handle up to 3A. I used #14. It's helpful to remove the fan in order to do this. However, depending on how you attack the LED, you might not have too.
Step 5: Soldering
Unfortunately, I don't have a good picture of this, but it turns out it's pretty hard to take pictures and solder at the same time.
Solder the + and - wires you've threaded through to the LED. The tab on the LED with two holes is the negative side, the tab with just one hole is the positive side.
I've also added a bit of electrical tape underneath the tabs in order to prevent shorts.
Step 6: Wiring the Driver
This is a simple step. Snip off the end of your laptop power supply, strip the ends, and measure polarity. If you don't understand, this guy does a great job.
Now that you've figure out the polarity, connect the + wire to the + screw terminal of the boost converter. Make sure you add it to the IN terminal, not the OUT terminal. They're clearly marked.
If you're using the other CC/CV boost converter, desolder the wire they give you and solder the + wire to the board. Do the same thing with the negative wire.
Some laptop power supplies have a 3rd wire, we cans safely snip it and ignore it. Plug in your power supply. If the green light pops on, you're golden! The other CC/CV boost converter may have a light, but it should work as well.
Step 7: Adjusting the Voltage/Current
Plug your multimeter test leads into the OUT screw terminal, taking care to make sure there are no shorts. On my boost converter, the voltage regulator is the pot where the screw is farther out. The current regulator is the pot where the screw is closer.
Adjust the voltage pot by twisting it clockwise. You should see the readout on your multimeter rise. Stop when you hit 33V. Then, adjust the current knob till it's at it's lowest setting. You should be set!
Step 8: Connecting + Troubleshooting
Connect the + and _ wires to the OUT screw terminals on your boost converter. Assuming you've done everything right, the light should pop on meekly.
You can then adjust the brightness via the CURRENT pot. LEDs are not linear devices, small changes in voltage produce big jumps in current. Use the current pot.
The fan isn't connected yet, so don't leave this thing on for hours. It'll burn up.
The middle picture is with the shop lights on. This thing is stupid bright. A typical 60W light bulb throws off 800 lumens, this will (minimum) throw off 10x that. People don't see increased brightness on at a linear rate either, so make sure to protect your eyes. You only get one pair.
Light won't stay on?
You either don't have a powerful enough power supply (100W+), or your power supply is detecting the sudden rush of .1-3A as a short. If it's the latter, try dialing down your current, then gradually taking it up.
Light never came on?
Check your connections. Check your solder joints. Check the polarity. Inspect the converter, mine was broken when it arrived. One of the mosfets wasn't connected, I fixed it, and the seller sent me a new one.
There's an annoying, high pitched whine!
This is a PWM problem. They've chosen a switching frequency you can hear. If it bothers you, trying decreasing the current, or getting a new laptop power supply.
Step 9: Connecting the Fan
Measure the polarity and make your connections. I snipped the end off, check the polarity, and wired it up. Remember, red is generally positive(+), black is generally negative (-).
You can ignore the other wire colors (white/yellow). Make sure to insulate your connections in some electrical tape or other nonconductive way.
Step 10: Finished!
Assuming everything's gone well, you should be done now. The fan works, light works, it's all good. I plug both the fan and laptop power supply into a timer, and use it to keep my two pepper plants doing well. You are free to mount this any way you'd like. Thanks, and vote for me in the Make it Glow contest!