As I’ve noted in a previous post, I am logging moisture and temperature data to an SD card. I wrote a small Python script to plot the data as time series. An example is shown in Figure 1.
Tag Archives: Arduino
Smart Horticulture, Part 2: Sensors and Actuators
The aim of the basic horticulture controller is to control the water supply to the planter boxes. It’s basically a limited controller, in the sense that I can either turn the water supply on or off, and I can only increase the soil moisture content and cannot decrease it actively. I tried a couple of cheap resistive soil moisture sensors but found them too inconsistent, and they corrode easily. There are some online designs for capacitative sensors, but I was curious to try the VG400 sensors from Vegetronix. Positives: consistent, do not corrode, and low power. Negatives: they’re expensive. There are a couple of additional negative points which I discovered the hard way and aren’t anywhere on their website. I’ll discuss them later.
In Pursuit of a Simple, COTS GPS/INS
GPS/INS (Global Position Systems / Inertial Navigation Systems) are used for a variety of applications (UAVs, robots, or even your more aggressive propulsive devices) which basically tell you where you are and how you are oriented (i.e. 3-dimensional position, velocity, and attitude). Anyone who’s taken a graduate course in estimation or filtering has probably written a version of a Kalman filter for GPS/INS applications. But I’ve never actually made one, so I decided to put together a few COTS components into the following:
Prasenjit Sengupta, Ph.D. 