Hacked Gadgets Forum

March 9, 2010

DIY Soil Moisture Sensor

at 8:39 pm. Filed under DIY Hacks


I recently bought some house plant seeds via a mail order seed company. I don’t seem to have the knack of caring for the seeds though. I followed the instructions on the packet but don’t seem to be having much luck in getting any of the seeds to sprout. I am thinking that next time I attempt this I will need some automation on my side. When I was looking into what some other people had done I came across this DIY Soil Moisture Sensor on The Cheap Vegetable Gardener site. There is also lots of cool information on the site for monitoring and controlling plant growing. If you have an extra PC case kicking around you can get some use out of that too!

“You should calibrate the sensor by getting a reading with the probe dry then again when it is full saturated in water.  Ironically, the probe I made was almost exactly specifications as the one I repurposed from a cheap commercial soil moisture sensor so I didn’t even have to modify the constants on the automated computerized grow box software.”



You try that able eliminate without has been leading www.renes-kirmeswelt.de/md/levitra_with_dapoxetine_generic.html . Is effective for treatment erectile the of ingredient is...

Related Posts

Mobile Phone controlled Plant Growbox
Talking Plant Project
Plants Watering Watcher-2
Bio Computer
Flood Triggered Automated Camera System
Grow Plants with no Soil using LEDs and Nutrient Mists
DIY Vacuum Motion Sensor Mouse Trap
WiFi Sensor for the LEGO Mindstorms NXT



4 Responses to “DIY Soil Moisture Sensor”

  1. Sirkka Says:

    Think I should let my husband to build this, then my plants want be dead when I come home from vacation. :o)

  2. AlmostThere Says:

    The real thing is called a “Gypsum Block”. I found I could measure the resistance between two probes and get an idea of the moisture content from that. So I set up a little “Test Unit” by filling a flower pot with moist soil and measured the resistance between two nickels (I chose nickel because it doesn’t corrode easily) and got about 2K Ohms. Wondering if temperature would affect the measurement, I put the “Test Unit” in the refrigerator overnight and the measurement went up to about 3.5K Ohms (did the soil loose some moisture overnight?) Next I put it in direct sun light for several hours to heat it up and the measurement went down to about 1.5K Ohms. Sure enough, not only does temperature affect the reading by approximately 7.5% per Degree C, but it appears that moist soil (at least the sample I’m using) has a negative temperature coefficient! (Almost all known conductive materials have a positive temperature coefficient where the resistance goes up with temperature, moist soil, however, goes down making it somewhat of a rarity.)

  3. Circuit Hack – How to Make a Moisture-Sensing Soil Sensor! Says:

    […] via hackedgadgets […]

  4. Mobile Phone controlled Plant Growbox - Hacked Gadgets - DIY Tech Blog Says:

    […] plants and adjust the environment you are providing for them on the fly. You probably remember the DIY soil moisture sensor and the LED plant grow box that we featured here before, they were also created by The Cheap […]

Internal Links:



Hacked Gadgets

Site Sponsors:

Nuts and Volts Electronic Labs Trossen Robotics Free Technical Publications Blue LED


Recent Comments:

More RSS Feed Options

Site Sponsors:


Interesting Sites: