LED Plant Light Update

I posted before about my idea for hydroponically growing food in my apartment, and using custom made LED grow lights.
… this is an update to that (hence the post title) 😛

I'm skipping the hydroponic part for now. It introduces too many variables at this stage, and since I've never implemented a hydroponic system, it would just be one more potential source of problems. I have built a test version of my LED grow light. It's not as powerful as I would like, but once again, it's just a prototype. It's currently using less than 2 watts of power, and the goal is to have 2 slightly larger versions.

The current setup is a 35 gallon plastic storage container, lined with reflective mylar to reduce light loss, and a layer of white wrapping paper behind that, to further reduce light loss (even though mylar is reflective, it's so thin that some light gets through, the wrapping paper prevents that light from being wasted). The LEDs are mounted on a solderless breadboard (the final version will be soldered onto a circuit board), and I'll skip the details of the voltages and light frequency of the LEDs.

I've had a Snake Plant in the box for about the last week, and it seems to be doing well. One of the dominant leaves has grown about 1.5-2" since moving to the box, while another comparably sized plant sitting in my window has grown less than half that. A couple of days ago I found some mint and chamomile seeds and planted those in there as well. The seeds are 2 years old, so I'm not sure if they're even still viable, but we'll see.

One thing I was worried about was whether or not it would be cost effective to set up a system like this. Some quick math shows that it costs almost nothing to power a system like this:

The light is on for 14 hours a day, and uses less than 2 watts. That's 28 watt-hours per day. Which is about 840 watt-hours a month. 1,000 watt-hours (1 kWh) is about $0.12. Even doubling the lights on this thing, the cost to run it per month would be less than $0.25.

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