Posts | Comments

Planet Arduino

I’ve been looking into creating an automated herbarium of some sort for a while, and I came across the brilliant post about creating some DIY soil moisture sensors using nails and plaster of paris. cheapvegetablegardener from hackaday.

Plaster of paris humidity sensor

Plaster of paris humidity sensor


Plaster of paris humidity sensor with wires attached

Plaster of paris humidity sensor with wires attached


Both of the sensors

Both of the sensors

I wont explain all of the theory or background as it is already explained on cheapvegetablegardener.

Resistance experiment on moisture sensor

Resistance experiment on moisture sensor

I measured the resistance of the sensor in air to be 12Kohms, I then placed the sensor into water (keeping the nail heads above the surface). The resistance dropped to 4Kohms whilst in the water, and then over 20 mins of back in air the resistance rose to 5.6Kohms. The sample still looks and feels quite wet, so I imagine it is going to take some time to dry, but from these prelimary results we can see it appears to work.

Soldering the wires to the nails before creating the plaster of paris along with covering the end sensor with hot glue would improve its longevity. I will post again once I find a better mould to make the plaster in as it was quite difficult to get them out of the cuvettes (I had about a 50% success rate).

Here is a microscope image of the surface of the plaster:

Microscope image of the surface of the plaster of paris

Microscope image of the surface of the plaster of paris

Comments are closed.



  • Newsletter

    Sign up for the PlanetArduino Newsletter, which delivers the most popular articles via e-mail to your inbox every week. Just fill in the information below and submit.

  • PlanetArduino is powered by WordPress. Design by Jasone.it. Valid XHTML   •   Valid CSS
    40 queries. 0,572 seconds.