Introduction: Grow Light and Irrigation Hood - 54W, 3300 Lumens, $18

By Martin Reed
About: Seafood is my specialty but my love of food justice, self-reliance and productivity knows no bounds. I grow food under my bed.

This project improves upon the first version of a grow light designed to fit on a PVC rack for baking pans.

1. Cheaper. Switched out pricey full-spectrum LEDs for standard CFLs. Plants are growing 10x faster with the increased light and bulbs are 1/10 the cost!

2. Smaller Footprint. Lights moved from top to sides shrinking vertical height by more than half so trays can stack vertically.

3. H20. An integrated irrigation system pumps water up and around a tube on top of the pan allowing nozzles to drip water (while avoiding the light bulbs).

Step 1: Gather Materials

Baking Pans (Standard 20”) - $0.60

*Lights - 4 @ 1.54 = $6.16

E27 Socket (common household size) - 4 @ $1 = $4

Plug and wiring - $3

1/2" Tube - 10ft @ .30/ft = $3.00

Irrigation nozzles - 10 @ .10 = $1 (details below)

Total cost per light = $17.76

Tools: Drill, 1” hole saw, 1/8” bit, glue

*Which of Amazon's two popular CFLs to buy? GE 13W. Lower cost and heat output without sacrificing lumen efficiency.

Philips 18W CFL = 2700K, 1200 lumens, 18W @ 2.99 = 400 lumens/$1 and 67 lumens/watt**
GE 13W CFL = 2700K, 825 lumens, 13W @ $1.54 = 535 lumens/$1 and 63 lumens/watt.

**Just as car fuel efficiency is measured in miles per gallon, lightbulb efficiency is the amount of light (lumens) produced for each watt of electricity consumed.

Step 2: Drill, Glue, Assemble, Wire

Video shows a time-lapse of the build.

1. Cut holes on side. 1" hole holds most sockets, but first check diameter. Stagger lights to ensure equal coverage. You can drill two or three pans stacked if you plan to build multiple fixtures.

2. Drill holes on bottom for irrigation nozzles. Ensure they won't drip on a light.

3. Glue tubing on the top over the holes drilled for the nozzles. Easily plug the end of the tube with hot glue.

4. Drill just into the tubing through the existing holes on the underside to fit nozzles. Attach nozzles with plenty of elbow grease.

5. Insert sockets and wire everything. Positive and negative from the wall to the first and second lights on one side. From the second light around the backside to the other two lights. Some electrical tape and heat shrink wraps hold everything neatly together. Some hot glue will hold wires flush with pan and secure the sockets.

Step 3: Irrigation Flow and Water Nutrients

Rain bird has three types of drip nozzles:
Blue = 0.5 Gallons per hour (GPH), Black = 1.0 GPH, Red = 2.0 GPH

I’ve found this generic version is a better deal and allows flow to be adjusted to provide a similar range.

A digital outlet can set to water in one-minute increments, which at 0.5 GPH is 2 Tablespoons of water per minute (TPM). So far, I have found that 20 minutes every other day is ideal for the microgreens growing in 60% humidity and mean temp of 75° F. A small pump sits in a basin of water with a small amount of dechlorinator and nutrients.

Quick reminder: The 3 numbers you see refer to the ratio of N-P-K.

N stands for nitrogen, which is responsible for strong stem and foliage growth. P is for phosphorus, which aids in healthy root growth and flower and seed production. K stands for potassium, which is responsible for improving overall health and disease resistance. For growth I like a ratio of 4-3-3 with added magnesium, a building block of the Chlorophyll that makes leaves appear green. BioThrive makes a great product. Just add 4T : 3 gallons of water.

If you notice two trays for the plants: one pan with holes drilled on the bottom nestles in another pan with clay pellets (or stones, etc.) Water can drain and maintain humidity. Lights are on 24 hours/day and I'm testing for optimal growth conditions. Thanks for reading!