Woo! After only a day the one of the sprouts has made a right turn towards the LEDs!!! You can see one sprig is still going towards the window still. It will be interesting to see if it turns as well.
Carrie’s drop watering scheme, which is a few days old, may have helped as well. Its an old flower holder/feeder. She worries that part of the problem may have been dryness from the hand watering we had been doing.
Well, my lettuce sprouts are dying. Of the four that spouted only one is left and is growing… straight towards the window. So, either the led modules are not putting out enough light or the light is the wrong color. To address this I designed a new module with almost double the LED density. The board will have 28 ultra bright blues in addition to 30 ultra bright reds. The chains have been reorganized into 6 in a row for red and 4 in a row for blue with an increased supply voltage of 15 volts. That reduces my future battery supply options, but to heck with it. I want growing lettuce!
Above you see two of the new modules being installed. With the higher supply voltage the old modules needed a change as they began to run at about 38mA, well above their 30mA maximum. So I put two blues into each chain of the old boards. That brought the current down to 15mA because the blues drop 3.2V each instead of the red’s 2.0V.
I have two more high density board toner-transferred and waiting to be etched, drilled and populated. Once they are on, I’ll give the lettuce a few more weeks before I try something new.
In very short order our lettuce has sprouted! It actually sprouted several days before we left for vacation on Dec 29th, less than 10 days after we planted.
We have four modules up and running right now. I was actually surprised at the speed at which the lettuce sprouted so now I am in a mad rush to build more modules so that the lettuce can receive its proper amount of illumination. I should be able to get another four modules built this week. Maybe more if I work it over the weekend.
First light for my LED modules! I’ve settled on all the parts and designed the PCB. The picture above shows the very first PCB module operating. 27 more of these and I’ll be ready to grow lettuce. Well, I still need to buy dirt ;)
You can see the 0.1″ thick traces in this photo as well as the barrel adapter that delivers power to the module. I need the thick trace since this is the only module that will have a barrel connector. I’ll link all the other modules to this one via the screw terminals. As such I need to make sure this module has the trace widths needed to carry 2 to 3 amps of current.
I read an article in 2005 about the Japanese growing lettuce indoors under pure red LED light. Ever since then I’ve had in the back of my mind that I’d sort of like to try it one day. My wife actually does grow a variety of herbs and vegetables in a plot in our backyard. Watching her enjoy her successes finally pushed me over the edge this year to actually attempt indoor lettuce.
So just today my baggie of 1000 LEDs came in. They are spec’ed at 8000mcd 10deg and altogether should put out about 190 Lumens. However, they are super-cheapo (2.5 cents/unit) so actual output may vary quite a bits.
I’m going to figure out what the average voltage drop is on the LEDs and then design a 4″x4″ series parallel PCB circuit that where the LEDs drop as close to my power supply voltage as I can get them. Then I can mass produce the circuits, put them above my 18″x26″ bucket of dirt and start planting seeds!