Using the new method of measurement, described in this post, I could successfully collect some meaningful data. This time, the read values are the exact values of the final sensor without a different kind of oscillator.
I watered the plant at day zero with quite a great amount of water. From there you can see how the frequency slowly rises, while the soil in the flower pot starts to get dry. There is a small measurement error between day two and three. Here I had a short power loss and no data was recorded which resulted in some zero records. Continue reading Successful Measurements→
I started a second take on the long term tests for the plant watering sensor. This tests are required to be sure, the measurements follow the expected cycles. After watering the sensor, the frequency should go down and while the soil is drying up, the frequency should go up the the initial value.
Logging this measurements is very important to get a good overview of the measurements and be sure if every aspect of the device works as expected. At this point, I especially test the sealing of the foot part of the sensor. If it keeps completely sealed against water, I should get very consistent and repeatable readings.
The curve on the right side shows the measurements of the last 48 hours. These small variations are normal and are most likely caused by the plant itself or because of temperature changes of the board.
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The first long term measurement I made, to test the behaviour of the sensor over a longer time range was a failure. After the five days with the device introduced in this post, the readings made absolute no sense.
The sensor was not moved in the flower pot and the plant was once watered at the begin of the measurement. While it looked promising at the begin, the frequency suddenly went down again, which was very irritating. I am still investigating how this could happen.
To get closer to the real measurement of the final plant watering sensor, I started a new approach.
I soldered a header to one of the LED pads on a fully assembled plant sensor. Next I changed the device for the measurements.