Hi Hackers, I am new to this community and relatively new to farming itself. This is our second year of production and its already time to start planting onions up here in Quebec. We have decided to start the Alliums indoors for the first month and move them out to the greenhouse at the beginning of April. We didn't feel that it was worth it to heat the greenhouse yet, when overnight temps are still regularly below 0. So as we did last year, we have moved a few greenhouse tables inside and set up 400 watt sodium halide lights above them. This worked pretty well last year. But this year I want to build an Arduino based timer to control the light cycles. I am already familiar with the Arduino's and have posted a tool wiki, on my basic setup of a "Temperature Data Logger".
The reason I think the Arduino is really good for this project is because I can control multiple circuits with one controller. This year we are using 4 lights. Plugged into a 15 amp cirucit, and 120 volts, that means we can have 1800 watts safely on that circuit. That technically would power all 4 lights (4 X 400= 1600). However there is some other household stuff on those circuits so I divided them up onto 2 circuits in the house to be safe. I will use a couple of powerswitch tails 2 to control the 2 circuits. The wiring and code looks pretty straight forward for this project, and I will try and document it as I go.
The question is what is the best light cycle to use? I have 1600 watts of light over about 90 sqft. or about 17.8 watts per sqft. I am curious what other are doing or would do for a light cycle. I have attached a graph showing the hypothetical differences. Up here in Quebec, it doesn't make too big of a difference as we only pay about $0.05/kilowatt hour. Cheap. But still curious as to what would be best. I haven't searched the internet much for an answer yet, I am sure somebody must have asked these questions before.