When this project began we knew that we’d have to have some sort of grow lighting if we planned on effectively growing throughout the long Michigan winters. I briefly explored the retail market for a lighting solution and quickly realized that option was not in the budget because each light was $1000+.
I’m moderately familiar with electronics and the thought of building my own lighting system wasn’t too much of a stretch. However, I had a list of details that I really wanted to explore and apply to the system I intended to build.
- A high bay type light that didn’t need to be 4″ above the plants.
- Had to effectively handle vegetative and flowing growth cycles
- The fewer the parts, the better (it’s a pain to get things even when hanging them from the dome roof).
- Ideally the lights would have a small footprint to minimize shading when not in use.
Seeing as this is a prototype aquaponics system, I didn’t want to get into a situation where I was juggling lights because my beds are growing a variety of plants. High bay lighting would also help keep the system minimal with few parts because you would be able to cover more square footage with less hardware.
Going into this project I really wanted to grow cut flowers and vine crops. The flowering stage prefers for red light and vegetative likes more bluish light. Now I really didn’t want to have to worry about tweaking lighting spectrums and there is data that shows high CRI (color rendering index) white light helps prevent stretching while eliminating the need to mess with different colors. CRI is a number between 0-100 that tells you how close the lighting source is to replicating full spectrum sunlight.
The Build
Modern grow lights may seem like a complicated thing to diy, but it’s pretty straight forward.
- Start with a light source (in this case a high powered LED)
- The LED needs some form of cooling, usually by mounting it to a heatsink and/or using a fan.
- Wire the LED to a LED driver. It’s basically a large AC adapter and performs a similar function as a ballast in a florescent light.
- Mount everything to a frame so it can be hung.
Taking our requirements above into account I decided that I wanted to build COB (chip on board) LED lights. These are super bright LED’s that have numerous diodes in an array on a single chip.
I decided to go with Bridgelux VERO 29 COB LED‘s. I chose these because while they run a bit hotter than other options, they have a 90 CRI, 12,000 lumen output, and are low cost when compared with other similar chips. For reference, your car high beams are around 2000 lumen, so these are super bright. These chips also come mounted in a holder and allows you to use a solderless connector (PICO-EZMATE HARNESS) that makes wiring easy. The COB is then mounted to a 133mm heatsink with the included screws and thermal paste.
I used the guides on the LED gardener website to choose all my parts. This is a fantastic resource that has guides from matching LEDs with the proper driver, diy assembly, and product testing.
16 lights total
After all the light were assembled it is time to mount them to our frame. We chose to mount the lights in groups of 2 on a 1/8 inch aluminum frame which we screwed together with small sheet metal screws. We decided on groups of 2 because that would be easier to hang in a circle around the dome. We made 4 foot lights for the parameter where we’re mainly growing greens and 2 foot lights for the center bed where we will be growing most of our vine crops
Now that the lights are mounted to the frames, we need a way to power them.
I went with a constant current driver decided to wire 2 fixtures (4 lights) in series. This decision was made out of simplicity and availability of drivers. A constant current driver provides a constant amount of amps (in this case 2.2 amps) and provides a higher voltage. We wire the lights in series because our voltage will be added as we connect more lights. You can wire your lights in parallel and use a constant voltage driver, but you do run the risk of your lights going into thermal runaway. This just means that as your lights get hotter, they draw more current, which makes them hotter, and draw more current, and eventually burn out. Both methods have their advantages and disadvantages.
Four lights wired in series. This means we connect all the lights positive to negative.
Alrighty, we have 16 lights wired in groups of 4, so we need 4 of the large Mean Well drivers. Mean Well drivers are what most people use in their builds and are industry standard. This particular driver has a a separate dimmer circuit that you can wire a dimmer into to control the power being sent to your lights. They do sell drivers with the dimmer built in, but you lose a lot of your water resistance if that’s important to you and you also can’t run all your drivers from one dimmer.
These Wago lever nuts make connecting wires easy. They’re especially useful for connecting solid core wire to stranded wire.
Installation
Considering these lights are purpose built for the dome layout (and the roof still leaks) I wanted to mount the drivers in a central location and run circuits to the light groups. One thing to remember is that the entire driver is grounded and if you’re mounting to you frame you have nothing left to do. Since we’re mounting these externally, we need to run a wire from the driver casing to a wire connected to each of the light frames. I also wanted to use disconnect plugs to make any maintenance/replacement easier and minimize any wiring that would need to be fixed.
In hindsight, I probably should have used a non-standard plug for the DC power outlets, but it’ll work for now. The drivers are mounted behind one of the greenhouse fans to help with cooling if needed and we run the DC circuits out through a junction box. The hanging wires you see are the dimmer circuits.
The final thing to do is hang the lights. I used adjustable ratchet hanging straps to hang the lights that allow me to easily raise or lower the lights as needed. They also offered a lot of flexibility when hanging the lights on the non-standard ceiling.
Well that’s the last of the large projects for the near future. We’re all cycled, planted, heated, lighted, and ready for the winter. I’ll be posting some more in depth guides of the various greenhouse components soon, but I’m always happy to answer questions in the mean time.