Grow with Arduino

I put the punchline in the title, so let me provide some justification and explanation. One of the things that initially excited me about the prospect of using the Launchpad was the presence of support on Linux. While not officially supported by TI, there is a project to add the msp430 family as a target for cross-platform gcc compilation. As an unsupported endeavor though, there exist some hiccups, both in compilation and communication with the launchpad under Linux.

Been a while, so let me catch up on what’s been going on. Mainly “real life” has been getting in the way of progress, but that’s not say nothing has happened. I made huge Digikey and Mouser orders to continue to build up my inventory and have the supplies needed to proceed. The process of putting those orders together and waiting for them to ship added to the delay. There were three categories of components I picked up.

“Wait,” I hear you say, “didn’t you already bore us enough?” Well yes, but I haven’t come close to exhausting soil moisture sensing techniques. Lucky, lucky you… Actually, I mainly forgot to cite my sources and give some handy links to more information! So rather than a thousand words on the many joys of capacitance sensing, here’s a link dump of some resources I found but didn’t mention last time.

I’m about to take of for a trip to Israel for work which, coming immediately after a visit by my parents has conspired to slow my progress. Today, I took a deep breath and started looking into moisture sensors in a serious way. Currently, I have two probes running – the Vegetronix V400 and a resistive sensor of two galvanized nails shoved into the soil. While i’m collecting data and waiting to compare the output, my goal is to have a bunch of sensors placed around my garden and i’d like them to be homogeneous so I don’t have to worry about multiple sensor peculiarities.

The moisture sensor works. Still some work to be done calibrating + tweaking signal levels to give it a wider range, but a swing from 350-450 (ish) is actionable. The first jump is where I discovered that I was using the wrong input voltage (5V instead of 3.3V). At the next leap, I watered then watched it decay over three days, watered again and watered near the very end. Basically, this puts the moisture sensor at the same point as the temperature sensor – it is behaving correctly but still need some hardware tweaking to get the best possible accuracy + range.

My parents are visiting, so I haven’t had much time to dig into anything too much recently, but I did tweak the temperature sensor. It appears to be giving much better readings now. Given this represents a 30+ degree swing in temperature, I really want a wider range in readings, but it will do for now. I’m considering switching to a 1-wire chip or something that includes additional weather data (like barometric pressure).

Quick update, but things are working!

You can see that I plugged it in near sundown. The increase near the end is where I turned on a light inside – the sensor is currently in a window pointing outside, but clearly isn’t very well isolated.

This plot will be more interesting tomorrow – basically the big jump is where I watered. It will be interesting to see how the moisture level changes overnight and in the sun during the day.

I’m certainly not the first person to think of building a watering system using arduino – here are some projects which have inspired me. As a bonus, I get to clean up my open browser tabs – I really need to be in ‘Too many tabs anonymous’. In no particular order… GardenBot Garduino Solar Powered Automated Garden Properduino Fully Automated LED Growbox How to make a Grow Box Controller .