Soil Moisture AND Temperature Sensing End Node Jan 26, 2017 19:02:51 GMT
Post by papa on Jan 26, 2017 19:02:51 GMT
Soil Moisture Sensing End Node
This thread was revised, starting April 15, 2020
Does my garden (or other soil) need watering today?
<< I have used this hand held soil tester (search here to purchase) to check my three raised garden beds (in growing weather). However, what if I could check via a Soil Moisture Sensing Node that reports to OpenHAB? With additional parts & programming later, it can even help control watering soil that needs it. This thread is a necessary beginning toward this ability. After you finish fulfilling this thread, continue with this UPDATED thread about Irrigation Automation.
For test purposes, I adapted the schematic, sketch, & text from here. Then I adapted the code to the computourist end node approach that I use in the choose_nodes sketch.
I suggest you start with building just a soil moisture test unit using an 3.3 volt Arduino compatible & a solderless breadboard (see the next post). Then install an RFM69 radio to make it an end node. Below are instructions for building an end node that can be powered by batteries.
Parts: One needs a 3.3 volt Arduino compatible, an RFM69 radio, a small solderless breadboard, some resistors (100 ohm & an 0 to 10 kilo ohms potentiometer), some corrosion-resistant probes, some wires to connect things, & maybe some heat shrink tubing & liquid electrical tape. The battery version in a post below requires other parts.
Probes need to be long enough to reach plants' root area & rise some from the soil's top. (I first used stainless steel skewers, but they corroded & became erratic after a year or so. In 2020, I switched to two 6 inch sections of coax cable. Strip each end of the cable down to the copper center. Strip a small amount on one end for soldering the connecting wire (24 inches?). Strip 1.5 inches on the cable's other end for inserting into the soil. Drill a hole in the center of two artificial wine corks, just big enough to tightly hold the still insulated part of the coax cable. Tape the two corks side by side. Insert probes into soil until cork bottoms touch the top of the soil.
Update, June 30, 2020: Coax cable's bare copper center does not have much surface so it may not reliably touch the soil nor reliably register moisture. Packing soil around the 2 copper probes seems to help. In the future, I may add another 1.5 or 3 inches of coax to strip for each probe. Then I would fold the stripped wire back upon itself to make 1.5 inches of stripped wire with a now larger surface.