55 lines
No EOL
2.3 KiB
Markdown
55 lines
No EOL
2.3 KiB
Markdown
# Experiment 01 - Sensor Calibration
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## Purpose
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The purpose of experiment 1 is to map the analog output values of the hydration
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sensor to different levels of water concentration in soil. This mapping will be
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necessary to adjust the user experience of the final device.
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## Components and equipment
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- Arduino board to run code
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- Three male to male jumper cables
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- One moisture sensor
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- A cup of soil
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- Water
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## Methodology
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1. Prepare the sensor. The power input should come from the 5V output of the
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board. This is important since different voltage inputs to the sensor will
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alter the obtained measurements for an identical humidity.
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2. Prepare the code. Three versions of the code will be used raw, slightly
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smoothed and heavily smoothed.
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- Raw version outputs the sensor's measurement to the serial port in
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real-time, unfiltered.
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- The slightly smoothed version will take 10 measurements with 50ms of
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delay between each and return the mean.
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- The heavily smoothe version will take 100 measurements with 50ms of delay
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between each and return the mean.
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3. Prepare the soil
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- In a small recipient (weight: 80g), place 200g of soil.
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- Let it dry for X days (collection on 24/10/2022) to obtain the driest
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possible soil.
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4. The next steps will be performed repeteadly by adding 10ml of water to the
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soil at each step. Start by first measuring the completely dry-soil. Ensure
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that the water is distributed uniformly across the soil. For each amount of
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water up to a max of 200ml, and for each version of the code:
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- Obtain measurements from the sensor. If the measurement is unstable,
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record the observed range and the most frequent value.
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5. Finally, obtain measurements in a glass of pure water, with no soil at all.
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## Results
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See file `exp01_sensor_calibration.ods`.
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## Conclusions
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The results where a bit dissapointing. The sensor signal was clearly moving
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when the dry soil received the first 10ml of water. But, from that point on,
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the next additions of water barely modified the returned signal. Eventually,
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there was no significant change in the sensor values. This is showing a
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sensitivity way below what I was expecting.
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I have been reading about some modifications in the circuit to improve the
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accuracy of the sensor. I'll design another experiment to try them out. |