A Better LED Growlight - 10000lm for $15.





Introduction: A Better LED Growlight - 10000lm for $15.

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.

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
  • Solder
  • Multimeter
  • Drill + drill bit (not pictured)
  • Pliers
  • 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!



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    15 Discussions

    In the screen shot he uses a CPU cooler and a led from DX.What is your opinion about buying the 100 watt led and driver board from DX? :)

    5 replies

    This LED comes in a couple of different wattages, it looks like he's using the 50W type. Honestly, this thing is way too bright for a desk lamp. At half the power, it'd still be crazy bright. DX is a fine place to buy it, just realize it will be more expensive and probably less reliable.

    oh! thanks,I thought dx to be cheaper,now I'll enquire at the local electronics stores.I have couple of questions.
    1)if I were to use a led for a desk lamp what wattage should I use so that it doesn't strain my eyes at the same time provide ample light?
    2)if I have to light up my balcony (around 4 feet by 6 feet,plus has a metal roofing,on the second floor)what wattage led would you suggest?

    eBay will be your best bet for a decent price. If you were planning on using it for a desk lamp, I would run it at the full voltage (34V), but at a reduced amperage. 500mA will give you a fairly bright light, those dimmers I linked in at the top will allow you to pick an appropriate light level. As a bonus, running the chip at reduced power will increase the efficiency. LEDs give off more light when more power is applied, but not at a linear rate. I.e, if I pump 20W into this, I might get 3000 lm. If I pump the full 100W, I only get 10,000lm. I made up those lm numbers, but you get the idea.

    As for lighting up your balcony, I'd make sure to choose a "warm white" LED, as it'll look nicer and should be the exact same cost wise. One chip running at full power should be fine for lighting your balcony up at a reasonable level. Just be aware that since it's a point source illumination, you'll get lots of shadows depending on where you stand.

    yes,a single point source will create harsh shadows(already have an incandescent bulb installed on the wall),well rope lights lining the roof are a bit impractical .So I'll try strip lights or a combination of 4 low wattage LEDs at the corners.
    also,thanks for the reply!! :)

    Do you know the PAR (photosynthetically active radiation) efficiency of the LEDs? Raw lumens is nice, but how much of that light can plants actually use? I use LEDs to grow plants, and more isn't always more when watts are involved. I don't have great faith in multi-purpose LEDs for plant growth, but it's an awesome high-bay shoplight design, though!

    1 reply

    You're right, lumens isn't the full story. Here the thing though - white LEDs are essentially 100% PAR. Here's why this is a big deal- white LEDs are basically 100% PAR including the blue light (radiation) that excites the phosphor. There are red LEDs that you can buy at the time of this writing that are +40% electrically efficient (electrical energy in, number of photons out), blues that are +50% efficient and whites that put out 140 lumens per watt. In fact, cree just broke 300 lm/w. Granted, these generic LEDs aren't that efficient, but still, no other technology, including HPS/MH, can touch those efficiency numbers. If you run these LEDs at around 60W, they become far, far more efficent.

    Hey Gran, just making sure here - are you connecting the 12V fan to 18V laptop power supply?

    1 reply

    No, doing so would probably fry it. I connect the fan to the 12V wall wart. Mkae sure you know the polarity. Sorry if that wasn't clear!

    As you probably know, white light is made up of all the colors - so I suppose you could call this "full spectrum". However, this, and just about every white LED out there uses a blue led with a phosphor coating to maximize efficiency.

    nice work. I have a single 10W chip, it's extremely bright. can't even imagine a 100W led. have you seen my work? thank you for sharing. I am looking out for a good heat sink.

    1 reply

    Yeah, 100Ws is quite a bit of light - I plan on building 10 or so chained together. Should throw off quite a bit of light. Your work is great! CPU coolers are some of the best deals I've found so far - Old school Pentium.