I'm using heat cable (Google the type shown in picture, or buy at Walmart) which will connect to a microcontoller (computing system) which will be controlled by thermocouples placed within each pot. The current sensor (the black thing shown encapsulated in orange rubber in the second picture, first row, and then exposed in the picutres that follow) turns the cable on when exposed to temeperature below 30 degrees and then off when it reaches 42 degrees. My system, controlled by sensory temeperature information provided by a thermocouple within each pot, will turn on at much higher temperatures. For example, when soil temperature drops below 72 degrees.
In prior years I used heat-pads that people use to warm aching joints. But they used more energy than this system since they were beneath tubs containing the tomato plants and not connected to the type of computing system I'll be using with these which will closely monitor the soil temperature, turning them on and off, rather than just the pad temperature controlling the on/off cycling of the pad as they're designed to do. The maximum power each tape uses, shown by the meter (Google for where to buy) I've connected one through, is around 37 watts. The heating pads were using 54 watts each. Anything in the grow room that requires power, translates into the cost of the vegetables that are grown, so I strive to minimize all aspects of energy consumption in whatever way I can without minimizing plant growth.
This page will be modified as the system progresses. So if interested in this project you may want to bookmark it and return later.
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