Introduction: Desktop Grow Light

The desktop grow light is designed for growing small plants like lettuce or herbs. It can also be used to start seedlings indoors before moving them outside.

Supplies

Tools:

  • 3D printer
  • Drill
  • M4 tap
  • ~4.5mm drill bit
  • 3.3mm drill bit
  • Soldering iron
  • Metric hex keys
  • Heat gun

Parts to buy (feel free to get equivalent or similar parts from other suppliers):

Parts to print:

  • Base
  • Upright
  • Heat sink bracket
  • Brackets

Step 1: Print the Frame

Print the 3 parts of the frame, and 4 brackets. The heat sink bracket, base, and brackets can be printed without support. The upright comes out better with support material to hold up the slot. Print all the parts lying on their sides.

Attachments

Step 2: Drill and Tap the Heat Sink

Print off the PDF drawing of the frame at 100% scale, cut it out, and tape it to your heat sink. Use a transfer punch to indent the aluminum for your drill bit. Drill all 3 holes with a 3.3mm bit. Tap all 3 holes with an M4 tap. Deburr the holes with a larger drill bit. Avoid biting too deep into the aluminum with the large bit because it is very thin.

Attachments

Step 3: Solder the COB LED

Split and strip the ends of your 2 conductor cable. Tin the LED contacts and the wires. Solder 1 conductor to the - terminal and the other to the + terminal. Make sure the wires go straight out radially from the chip so they will go through the channels in the COB holder. The wire I listed in the supplies has 1 of the conductors marked with thicker stripes of insulation. I always use the marked conductor on the - terminal.

Step 4: Drill Out the COB Holder

Since we made all 3 holes on the heat sink M4, we need to drill out the COB holder for 4mm screws. Use your 4.5mm drill bit to enlarge the holes. We could have used M3 screws instead, but we prefer to use M4 because it's so easy to tear out M3 threads when you are tapping a thin piece of aluminum.

Step 5: Apply the Thermal Compound

Clean the heat sink with acetone. Put a bit of thermal compound in the middle of the heat sink. Spread it very thinly where the chip will be.

Step 6: Mount the COB LED

Put the LED in the holder and line the holder up with the holes. Make sure the wires from the LED are going through the channels in the holder so everything sits flat on the heat sink. Secure the COB holder with 2 M4x12mm screws. LEDil recommends max torque 0.6Nm. If you don't have a torque screwdriver or wrench that goes that low, just go by feel. That's about 20N at 50mm, or 5lb at 1in.

Step 7: Wire the LED Driver

Wire the - side of the LED to the - side of the LED driver output, and likewise with the + side. Cut off the receptacle end of your extension cord and wire neutral to blue and hot to brown. We use crimp butt connectors for this, but you could also solder everything and then insulate with heat shrink tubing.

Step 8: Test the LED

Plug the LED driver in at this point to make sure the LED turns on. Then unplug it to finish the assembly.

Step 9: Finish the Assembly

Use an M4x12mm screw to connect the heat sink to the heat sink bracket. Push the cable into the channel of the 3D printed part. Use 4 M3x25mm screws and nuts to connect the heat sink bracket to the upright. Again, push the cable into the channel. Finally, use 4 more M3x25mm screws and nuts to connect the upright to the base.

Step 10: Set the Timer

Plug the timer into an outlet and the LED driver into the timer. Push sections of the timer down for when you want the light on. Twist the timer to the current time. Make sure the switch on the side of the timer is set to use the timer, not set to always on. Now put a plant under there and watch it grow!

Step 11: Growing Tips

  • You can get seedlings to grow faster by stacking things under your container to put the plant closer to the light. Move the plant down as it grows to prevent it from being burned.
  • Having a fan blow on the plant will make it grow faster, but it will also mean you have to water more often.
  • Most plants grow faster hydroponically. You can improve the efficiency of your grow by using a hydroponic nutrient solution.
  • If you want to grow larger plants indoors, we highly recommend getting a grow tent. You can use several of the same heat sinks and LEDs as the desktop grow light to make a larger, more powerful grow light!