Allen Mulvey amulvey.com> writes: >=20 > My daughter and son in law operate a perennial nursery. > Several years ago I built a misting system for one of their > greenhouses. It works fine - all analog, no smarts. A > misting duration of about two seconds every twenty minutes > or so usually does the job. If the weather changes someone > needs to manually alter the interval. I would like to make > another, microcontroller, version which monitors the > temperature and relative humidity and makes appropriate > changes. I know there are a lot of other factors involved > but they have standardized on soil, pot size, etc. so most > of those are relatively constant. It is gross changes in > temperature and relative humidity that seem to be most > important. There is no wind in the greenhouse. >=20 > Are there any algorithms or charts available which would be > helpful in computing the necessary changes? >=20 > Allen >=20 >=20 I see several approaches: 1. Go all scientific about it, measure as many parameters as possible, such as T, RH, amount of light (direct sunlight and cloud), soil moisture, soil pH, etc. Then build (or use an existing algorithm likely used by big greenhouse operators. Should be published somewhere in trade journals) algorithm to control misting.=20 2. Measure only T and RH as you intend, and then have some algorithm to control misting. Record data over time and see what works best. 3. Record (as in write down, video record etc, and formalize) procedure ho= w people adjust misting time/interval. Very often people will use factors no= t "obvious", such as how comfortable they feel. Which might translate in a combination of T, RH, light intensity, time of day... If what is done now is satisfactory and the desire is to automate, approach #3 might be the easiest. =20 Sergey Dryga http://beaglerobotics.com --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .