Sensing Soil Moisture: You’re Doing it Wrong!

If you compulsively search online for inexpensive microcontroller add-ons, you will see soil moisture measurement kits. [aka] built a greenhouse with a host of hacked hardware including lights and automatic watering. What caught our attention among all these was Step 5 in their instructions where [aka] explains why the cheap soil sensing probes aren’t worth their weight in potting soil. Even worse, they may leave vacationers with a mistaken sense of security over their unattended plants.

The sensing stakes, which come with a small amplifier, work splendidly out of the box, but if you recall, passing current through electrodes via moisture is the recipe for electrolysis and that has a pretty profound effect on metal. [Aka] shows us the effects of electrolysis on these probes and mentions that damaged probes will cease to give useful information which could lead to overworked pumps and flooded helpless plants.

There is an easy solution. Graphite probes are inexpensive to make yourself. Simply harvest them from pencils or buy woodless pencils from the art store. Add some wires and hold them with shrink tube, and you have probes which won’t fail you or your plants.

Here’s some garden automation if this only whet your whistle, and here’s a robotic friend who takes care of the weeds for you.

Boost your garden’s output using ultrasonic mist

ultrasonic_aeroponic_growing_rig

If you enjoy gardening, it’s never too early to start thinking about next year’s growing season. [Jared Bouck] over at InventGeek loves his tomatoes, but the slow grow rates of his dirt-bound plants were less than impressive. To get things moving faster, he created a low-cost aeroponics system that uses ultrasonic mist to produce some pretty impressive results.

The construction process of this ultrasonic aeroponics rig looks dead simple, and [Jared] said that he had everything assembled in about half an hour. A cheap ultrasonic mister was mounted in the bottom of a plastic tub, and holes were cut in the tub’s lid to make room for his growing baskets. Tomato seedlings were wrapped in rock wool and placed in a clay growing medium, suspended over the water bath. The mister was turned on, and after just a few days, the results were obvious.

In the last step of his tutorial, he compares his aeroponically grown plant to one grown in soil – the difference is unbelievable. Considering how reasonably priced his setup is, it seems like a no-brainer to start growing your entire vegetable garden this way.