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154 lines
7.3 KiB
154 lines
7.3 KiB
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"original_hash": "70e5a428b607cd5a9a4f422c2a4df03d",
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"translation_date": "2025-08-28T20:39:44+00:00",
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"source_file": "2-farm/lessons/1-predict-plant-growth/virtual-device-temp.md",
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"language_code": "en"
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# Measure temperature - Virtual IoT Hardware
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In this part of the lesson, you will add a temperature sensor to your virtual IoT device.
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## Virtual Hardware
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The virtual IoT device will use a simulated Grove Digital Humidity and Temperature sensor. This keeps this lab consistent with using a Raspberry Pi with a physical Grove DHT11 sensor.
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The sensor combines a **temperature sensor** with a **humidity sensor**, but in this lab, you will focus only on the temperature sensor component. In a physical IoT device, the temperature sensor would be a [thermistor](https://wikipedia.org/wiki/Thermistor), which measures temperature by detecting changes in resistance as the temperature changes. Temperature sensors are typically digital sensors that internally convert the measured resistance into a temperature in degrees Celsius (or Kelvin, or Fahrenheit).
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### Add the sensors to CounterFit
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To use a virtual humidity and temperature sensor, you need to add the two sensors to the CounterFit app.
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#### Task - Add the sensors to CounterFit
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Add the humidity and temperature sensors to the CounterFit app.
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1. Create a new Python app on your computer in a folder called `temperature-sensor` with a single file named `app.py`, set up a Python virtual environment, and add the CounterFit pip packages.
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> ⚠️ You can refer to [the instructions for creating and setting up a CounterFit Python project in lesson 1 if needed](../../../1-getting-started/lessons/1-introduction-to-iot/virtual-device.md).
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1. Install an additional pip package to add a CounterFit shim for the DHT11 sensor. Make sure you install this from a terminal with the virtual environment activated.
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```sh
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pip install counterfit-shims-seeed-python-dht
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```
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1. Ensure the CounterFit web app is running.
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1. Create a humidity sensor:
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1. In the *Create sensor* box in the *Sensors* pane, open the *Sensor type* dropdown and select *Humidity*.
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1. Leave the *Units* set to *Percentage*.
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1. Ensure the *Pin* is set to *5*.
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1. Click the **Add** button to create the humidity sensor on Pin 5.
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The humidity sensor will be created and appear in the sensors list.
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1. Create a temperature sensor:
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1. In the *Create sensor* box in the *Sensors* pane, open the *Sensor type* dropdown and select *Temperature*.
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1. Leave the *Units* set to *Celsius*.
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1. Ensure the *Pin* is set to *6*.
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1. Click the **Add** button to create the temperature sensor on Pin 6.
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The temperature sensor will be created and appear in the sensors list.
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## Program the temperature sensor app
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The temperature sensor app can now be programmed using the CounterFit sensors.
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### Task - Program the temperature sensor app
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Program the temperature sensor app.
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1. Ensure the `temperature-sensor` app is open in VS Code.
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1. Open the `app.py` file.
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1. Add the following code to the top of `app.py` to connect the app to CounterFit:
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```python
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from counterfit_connection import CounterFitConnection
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CounterFitConnection.init('127.0.0.1', 5000)
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```
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1. Add the following code to the `app.py` file to import the required libraries:
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```python
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import time
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from counterfit_shims_seeed_python_dht import DHT
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```
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The `from seeed_dht import DHT` statement imports the `DHT` sensor class to interact with a virtual Grove temperature sensor using a shim from the `counterfit_shims_seeed_python_dht` module.
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1. Add the following code after the code above to create an instance of the class that manages the virtual humidity and temperature sensor:
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```python
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sensor = DHT("11", 5)
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```
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This declares an instance of the `DHT` class that manages the virtual **D**igital **H**umidity and **T**emperature sensor. The first parameter specifies that the sensor being used is a virtual *DHT11* sensor. The second parameter specifies that the sensor is connected to port `5`.
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> 💁 CounterFit simulates this combined humidity and temperature sensor by connecting to two sensors: a humidity sensor on the pin specified when the `DHT` class is created, and a temperature sensor that runs on the next pin. If the humidity sensor is on pin 5, the shim expects the temperature sensor to be on pin 6.
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1. Add an infinite loop after the code above to poll the temperature sensor value and print it to the console:
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```python
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while True:
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_, temp = sensor.read()
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print(f'Temperature {temp}°C')
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```
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The call to `sensor.read()` returns a tuple of humidity and temperature. You only need the temperature value, so the humidity is ignored. The temperature value is then printed to the console.
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1. Add a small sleep of ten seconds at the end of the `loop` since temperature levels don't need to be checked continuously. A sleep reduces the power consumption of the device.
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```python
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time.sleep(10)
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```
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1. From the VS Code Terminal with an activated virtual environment, run the following to execute your Python app:
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```sh
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python app.py
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```
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1. From the CounterFit app, change the value of the temperature sensor that will be read by the app. You can do this in one of two ways:
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* Enter a number in the *Value* box for the temperature sensor, then click the **Set** button. The number you enter will be the value returned by the sensor.
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* Check the *Random* checkbox, and enter a *Min* and *Max* value, then click the **Set** button. Every time the sensor reads a value, it will read a random number between *Min* and *Max*.
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You should see the values you set appearing in the console. Change the *Value* or the *Random* settings to see the value change.
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```output
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(.venv) ➜ temperature-sensor python app.py
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Temperature 28.25°C
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Temperature 30.71°C
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Temperature 25.17°C
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```
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> 💁 You can find this code in the [code-temperature/virtual-device](../../../../../2-farm/lessons/1-predict-plant-growth/code-temperature/virtual-device) folder.
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😀 Your temperature sensor program was a success!
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---
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**Disclaimer**:
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This document has been translated using the AI translation service [Co-op Translator](https://github.com/Azure/co-op-translator). While we aim for accuracy, please note that automated translations may include errors or inaccuracies. The original document in its native language should be regarded as the authoritative source. For critical information, professional human translation is advised. We are not responsible for any misunderstandings or misinterpretations resulting from the use of this translation. |