When measuring soil moisture down several feet you need a good sensor. Watermark makes a great sensor but it is quite expensive and needs a special circuit to read it properly.

A home made Gypson sensor is easy and inexpensive to make. It doesn't last as long but

it gives comparable readings to the professional sensor. It unfortunately needs the same circuit to read it properly but that is included. Simple to make and only has one critical component a .1 uf film capacitor.

I've made several of these over the years to monitor a couple of positions around my foundation that when they get too dry the building starts to move.

To build the sensor you attach low voltage outdoor light wire to 2 U shaped stainless rods. You need to silver solder them or use a spot welder to put on a nickel tab that is solder able.

Put the wiring in the printed form and poor in the Gypson. I've provided a chart to see how long it takes the sensor to become completely dry. I've also included a schematic of a circuit that puts out a frequency that is relative to the moisture of the sensor. Read this with a microcomputer and send off the data. These are slow response so once a day is plenty.

The unit is designed to fit in the end of a 1 inch schedule 40 pipe to push it into the predrilled hole. These are NOT designed to be driven into the ground. I first drill a hole about 3 feet deep. Take some of the dirt and make a slurry and poor it down the hole and insert the sensor into the mud. This insures a good contact to the surrounding soil.

I hope this is useful in some way or just gets you thinking.

Cheers

Kisssys

Category: Outdoor & Garden