2.5 KiB
Build a more efficient watering cycle
Instructions
This lesson covered how to control a relay via sensor data, and that relay could in turn control a pump for an irrigation system. For a defined body of soil, running a pump for a fixed length of time should always have the same impact on the soil moisture. This means you can get an idea of how many seconds of irrigation correspond to a certain drop in soil moisture reading. Using this data you can build a more controlled irrigation system.
For this assignment you will calculate how long the pump should run for a particular rise in soil moisture.
⚠️ If you are using virtual IoT hardware, you can work through this process, but simulate the results by increasing the soil moisture reading manually by a fixed amount per second the relay is on.
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Start with dry soil. Measure the soil moisture.
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Add a fixed amount of water, either by running the pump for 1 second or by pouring a fixed amount in.
The pump should always run at a constant rate, so every second the pump runs it should supply the same amount of water.
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Wait until the soil moisture level stabilizes and take a reading.
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Repeat this multiple times and create a table of the results. An example of this table is given below.
Total Pump time Soil Moisture Decrease Dry 643 0 1s 621 22 2s 601 20 3s 579 22 4s 560 19 5s 539 21 6s 521 18 -
Work out an average increase in soil moisture per second of water. In the example above, each second of water decreases the reading by an average of 20.3.
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Use this data to improve the efficiency of your server code, running the pump for the required time to get the soil moisture to the level needed.
Rubric
| Criteria | Exemplary | Adequate | Needs Improvement |
|---|---|---|---|
| Capture soil moisture date | Is able to capture multiple readings after adding fixed quantities of water | Is able to capture some readings with fixed quantities of water | Can only capture one or two readings, or is unable to use fixed quantities of water |
| Calibrate the server code | Is able to calculate an average decrease in soil moisture reading and update the server code to use this | Is able to calculate an average decrease, but cannot update the server code, or is unable to correctly calculate an average, but uses this value to correctly update the server code | Is unable to calculate an average, or update the server code |