I recently got sent a YL-39 and YL-69 soil humidity kit.
This kit is not hard to get operational, hook it up, connect to your choice of microcontroller, read the values (analog or digital) and do something with the information. The sensor works by measuring the resistance between the two legs of the PCB sensor. It does this by applying a voltage across the lega of the PCD sensor, and measuring the current flow.
Basically, this is kit that you can play with, but, DO NOT leave operational without thinking it through. This kit is not going to be reliable as the PCB sensor will be destroyed by galvanic corrosion.
Basically, this sensor is a toy. It is not useful in any real application. The PCB material will potentially absorb water and therefore change sensors performance. And, if you leave the sensor powered then you will have great fun with galvanic corrosion.
If you want to use. DO NOT leave the sensor powered. When you want to take a reading, power the sensor for maybe a few seconds (to settle the sensor) and take your readings. Then power it off again. Do not take readings too often. And, periodically you should invert the pins of the electrical connection between the PCB board and the sensor. This will reduce the amount of galvanic corrosion.
But, this is not all bad. I have operational damp sensors, they have been operational for many years, as least 5 years, and the sensors have not corroded. The circuit avoids galvanic corrosion by implementing a AC bias solution at an alternating frequency at about 1Khz. When I get a moment I may adapt the YL-39 + YL-69 Soil Humidity Kit to AC bias to prevent galvanic corrosion.
Anobium
Last edit: Anobium 2016-07-11
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I recently got sent a YL-39 and YL-69 soil humidity kit.
This kit is not hard to get operational, hook it up, connect to your choice of microcontroller, read the values (analog or digital) and do something with the information. The sensor works by measuring the resistance between the two legs of the PCB sensor. It does this by applying a voltage across the lega of the PCD sensor, and measuring the current flow.
Basically, this is kit that you can play with, but, DO NOT leave operational without thinking it through. This kit is not going to be reliable as the PCB sensor will be destroyed by galvanic corrosion.
Basically, this sensor is a toy. It is not useful in any real application. The PCB material will potentially absorb water and therefore change sensors performance. And, if you leave the sensor powered then you will have great fun with galvanic corrosion.
If you want to use. DO NOT leave the sensor powered. When you want to take a reading, power the sensor for maybe a few seconds (to settle the sensor) and take your readings. Then power it off again. Do not take readings too often. And, periodically you should invert the pins of the electrical connection between the PCB board and the sensor. This will reduce the amount of galvanic corrosion.
But, this is not all bad. I have operational damp sensors, they have been operational for many years, as least 5 years, and the sensors have not corroded. The circuit avoids galvanic corrosion by implementing a AC bias solution at an alternating frequency at about 1Khz. When I get a moment I may adapt the YL-39 + YL-69 Soil Humidity Kit to AC bias to prevent galvanic corrosion.
Anobium
Last edit: Anobium 2016-07-11
Very interesting ...
I am waiting...
When I get a moment I can draw up my circuit. It is really simple with a little thinking it worked.
This is the circuit I used. I checked the strip board today. Looks wonderful...and, the damp sensor works!
This diagram also shows the analysis from my scope today.