Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!sarah!cs.albany.edu!crdgw1!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!rphroy!rinhp825.gmr.com!vbreault From: vbreault@rinhp825.gmr.com (Val Breault) Newsgroups: sci.electronics Subject: Re: moisture sensors Message-ID: <52977@rphroy.UUCP> Date: 10 May 91 21:09:22 GMT References: <1991May10.173139.1371@solbourne.com> Sender: news@rphroy.UUCP Reply-To: vbreault@gmr.com Distribution: usa Organization: General Motors Research Lab. Warren, MI Lines: 57 Nntp-Posting-Host: rinhp825.gmr.com In article <1991May10.173139.1371@solbourne.com>, daveh@solbourne.com (Dave Helms) writes: |> Hello, |> I have an underground irrigation system in my yard and |> as a result cannot tell how wet different parts of the yard are. My |> question is does anybody know how I can buid some sort of moisture |> sensors to insert at different locations in my yard ? My neatest idea |> would be to have these moisture sensors placed a few inches under the |> ground and transmit into my house via telemetry. Wow, then I could hook this |> up to my mac and have a graphic representation of the moisture content |> in the yard. But I am problably being silly. Thanks for any responses. |> Dave Not really silly, but you're complicating it a bit. If all you want is a relative idea of how much water is in one area or another, you can try this: Bury a grid of wires below the surface by slitting the sod and placing the wires in the slits. Use insulated wires, but strip the insulation off the wires where they overlap. Do not allow the bare wires to touch each other, but seperate them with an insulator of a known size. By measuring the resistance where any pair overlap, you can get an idea of how much moisture is in the ground at that point. More resistance = less water. Less resistance = greater water. You can use your computer, if you wish. You'll need a switching array, analog to digital converter, and voltage source. You'll have to handle things like electrical noise, switching times, and other things that plague high speed A/D conversion. I suppose an easier solution would be to wire up the grid to a rotary switch with an appropriate number of positions (example would use 9) and use whatever VOM you have handy. It wouldn't have the swell graphical display, and may take the better part of a minute to read and interpret the data, but it's do-able in one Saturday morning, leaving the afternoon free for loafing. | | | | | | -----+-----+-----+- | | | -----+-----+-----+- | | | -----+-----+-----+- | | | Simple problems should have simple solutions. ------------------------------------------- Val Breault - vbreault@gmr.com The opinions expressed by the author do not necessarily reflect the position of the General Motors Research Laboratories or the General Motors Corporation.