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.
Category Archives: Blog
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:
Plug for Mountain View Kendo Dojo
Sharing a video by N. Provos, showing kendo practice at Mountain View Kendo Dojo. Visit us if you can! More information at http://www.mountainviewkendo.org.
On Didymium
Didymium filters, also known as the “poor man’s sky glow filter” are used as safety goggles by glass blowers. Didymium glass selectively blocks the radiation component emitted by sodium in glass (589 nm), which is also the predominant component of regular sodium-vapor street lamps.
Prasenjit Sengupta, Ph.D. 