Thanks, these are interesting articles. The first case won't work. Most plants rot if kept wet. They need to dry a bit before the next spray. We had looked at some artificial leaf systems. The ones I looked at were for irrigation not misting so this one is very interesting. If I recall correctly, Cornell worked on artificial leaves more than a decade ago. My daughter, who has a couple of degrees in this and a couple of decades experience says they don't work very well in the real world. The original artificial leaves used a material that mimicked the porosity of real leaves and their moisture content was read. A stainless steel version that holds and weighs the water is different but around here, upstate NY, mineral buildup would quickly upset the balance. In addition to the natural hard water substances are frequently intentionally added to the water to promote growth. Having said that, this makes me wonder if it would be possible to collect some of the spray into a container, then by controlling the surface area, hence the rate of evaporation, use that to trigger the next pulse. This is what I was hoping for from this list. I'm going to think about this and do some experiments. I'm not sure how to handle mineral buildup though. I suppose I could just swap out parts every week or so. Use one while one soaks in CLR or something. Allen -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Denny Esterline Sent: Sunday, May 05, 2013 3:05 PM To: Microcontroller discussion list - Public. Subject: Re: [OT] Greenhouse misting This link, http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1 282/F-6708web.p Suggests a more brute-force approach. A couple sensors are suggested, but effectively putting a measuring device next to the plant and keeping the sensor wet. This link, http://www.greenhousemegastore.com/category/misting-fogging Has such sensors commercially available (electronic leaf, $235 US) So clearly such things are used. -Denny On Sat, May 4, 2013 at 5:40 AM, Allen Mulvey wrote: > 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. > > Are there any algorithms or charts available which would be > helpful in computing the necessary changes? > > Allen > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 --=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 .