5.3 KiB
+++ categories = ["build","plants"] tags = ["houseplants", "grow-lights", "lighting"] date = 2025-01-01T16:30:00Z description = "Building winter grow lights for houseplants from LED bulbs, EMT conduit, electrical fittings, and a later grow-panel upgrade." draft = false slug = "grow-lights" title = "💡 Houseplant Grow Lights" author = "nicholas" +++
It is winter and the days are short and dark. House plants grow better with more light. I will build two grow lights using off the shelf electric supplies.
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Summary
The plants sit on a wire shelf cart. Some are not looking so good. The 4 notched posts that support the shelves are hollow inside, with an inner diameter that is a bit more than the outer diameter of 1/2" EMT conduit. This is lucky, as it allows me to slot in a length of EMT conduit upon which I build the rest of the lamp. I am able to rotate the conduit inside the posts to change the direction of light, and the lamp holder adds an additional degree of freedom by allowing me to change the vertical tilt of the lamp. There is enough slop / allowance between the cart posts and the conduit that rotate easily, but not so much that the lamp is unstable. Thanks to electrical standards, all of the components I build off of the EMT conduit can be made compatible with each other. I plug an outlet strip into a remote switch my parents gave me for my birthday. The plants now reach directly upward instead of angling toward whichever direction the window happens to be that day (the cart moves a lot). The cart can still move around even tethered to a wall outlet. Mounting the lamps to the cart means no floor clutter to bump into. I am pleased with how the build process went, and the result.
{{< image src="images/plant-cart-lights-on.JPG" caption="Plant cart with lights ON" >}}
{{< image src="images/grow-light-close.JPG" caption="Light close up" >}}
Parts List
{{< image src="images/components.jpg" caption="Parts" >}}
LED Bulb
I chose a 5000K 25 W PAR38 bulb with 40 degree light cone.This gives great coverage and minimal wasted light. A second bulb was purchased on clearance at Menards for less than $5.00, a price which matches its performance. It gets terribly, hot, does not produce nearly as much light as the other at roughly the same power, and has a very wide angle light cone. I do not mind any of this for such a price, though. This is not a serious growing operation and frankly the plants get enough light to do just fine through the winter anyway. The color temperatures of the bulbs are matched to daylight \ full spectrum light. Nearly all of the houseplants that sit atop the cart benefit from bright indirect daylight, which is something like 10,000-20,000 lux. I use an app on my phone to measure the illuminance (lux), which I understand is not as precise as a proper light meter. Once again, this is good enough. Several apps converge on around the same "measurements" of illuminance, and many have confirmed that the apps get close to the values measured on light meters. Placed just at the tops of the plants, my phone produces a reading of ~15,000 lux. Great.
EMT Conduit
I bought two (2) 5' lengths of 1/2" EMT Conduit because 10' would not fit inside a small car. I wanted a little bit of extra height to take full advantage of the beam angle of the floodlight, but it turns out that the few inches of additional height would not nearly have been worth the trouble of hack sawing my way through the metal tubes.
Wiring
I had a couple of extension cables that I trimmed the female leads off. I stripped back ~6" of the outer sheathing and secured them into a cord grip connector that screws into the threaded hole on the electrical box that is fastened to the end of the conduit. I wired everything up, white to white, black to black. It is a bad idea to rely on color alone at such voltages, so I verify hot, neutral continuity across the plug conductor and the lamp socket conductor. Everything checks out, so I screw on the wire nuts.
Final Assembly
I slide the conduit in the cart post, close up the box by screwing on the face plate. I attach the box to the top of the conduit by sliding the set-screw connector over the conduit and tightening the screw. I plug it in, and voila.
Thoughts
The loop of flexible cord sprouting from the top of the box looks only a little bit silly. There is a cleaner way to do this involving more fittings and more time, but it is acceptable to me considering this is a seasonal cart adornment. I could route the wires internal to the conduit, attach a second box at the bottom, put a dimmer switch in it. Wire it to an IoT relay switch for automated control. Endless possibilities. Realistically I will do none of these things as there is almost no additional benefit to me or the plants, but it is satisfying to think how painless it would be to expand the system. I am happy that 2025 is going according to plan.
Update - Added Grow Panel
We bought a 2 ft. shop light from Harbor Freight Tools and zip-tied it to the underside of the top shelf. Now all of the plants on the cart get great light year-round.
{{< image src="images/grow-light-panel-light.JPG" caption="Plant light panel" >}}
{{< image src="images/grow-light-panel.JPG" caption="Plant light panel" >}}