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.
Category Archives: Electronics
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.
Smart Horticulture, Part 1: Infrastructure
I’ve been meaning to set up some kind of automated horticulture system to grow herbs and vegetables for a while. The primary motivation hasn’t been the fruit of my labor, as much as it has been to experiment with – and to learn how to use – sensors, actuators, and microcontrollers. Progress has been slow; I usually only get time to work on it on weekends, and I’ve made several mistakes on the way. The project also revealed many problems with sensors that aren’t typically documented, but have to be solved anyway.
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. 