Automated plant watering

[alexbox]

I would like to build a circuit to automatically measure the dryness of the soil in a hanging basket and then water it when required. Some type of soil probe and a water solenoid set up.
Any ideas?

[Gazza]

I would like to build a circuit to automatically measure the dryness of the soil in a hanging basket and then water it when required. Some type of soil probe and a water solenoid set up.
Any ideas?

If I was doing this, I would use a Microcontroller. I have no experience in soil sampling, so I don't know what the proper device is, I did find this. http://www.berryhilldrip.com/Irrometr.htm#Model%20'R

You could set up the controller to monitor the output level of the sensor and set up some limits, at a low level for moisture, trigger a solenoid to a water reservoir, at the high level of moisture turn off the solenoid.

[audioguru]

I am using many of the Plants Watering Watcher-2 devices and discovered that different types of soil and water have a different resistance. Distilled water (rain?) is an insulator while my tap water conducts the same as salt water. Perilite is also an insulator but soil with some fertilizer salts conducts well.

If soil has been dry too long then sometimes it take up to an hour for it to absorb water.

My circuit uses an AC signal because DC would cause unplating and corrosion of its probes.
http://www.electronics-lab.com/projects/science/018/index.html

[MP]

Hi Alex,
Firstly, Welcome to the forum!
Do you have experience programming a micro? This would be the most interesting way to do it. Otherwise, you might want to use a timer. Either way, you really do not need a water monitor, per se. You just need a circuit that will activate a relay at a predetermined moisture level or predetermined time interval.
For either application, since the moisture in the soil changes the resistance of the soil, you can use a circuit which uses the resistance of the soil in a voltage divider to activate a comparator or transistor, then to a relay that activates the watering mechanism. For the timer idea, you would want to build a clock circuit and activate the relay at predetermined time periods.

Hopefully, this gives you some ideas. Good luck with the project!

MP