You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
141 lines
6.2 KiB
141 lines
6.2 KiB
# Measure temperature - Virtual IoT Hardware
|
|
|
|
In this part of the lesson, you will add a temperature sensor to your virtual IoT device.
|
|
|
|
## Virtual Hardware
|
|
|
|
The virtual IoT device will use a simulated Grove Digital Humidity and Temperature sensor. This keeps this lab the same as using a Raspberry Pi with a physical Grove DHT11 sensor.
|
|
|
|
The sensor combines a **temperature sensor** with a **humidity sensor**, but in this lab you are only interested in the temperature sensor component. In a physical IoT device, the temperature sensor would be a [thermistor](https://wikipedia.org/wiki/Thermistor) that measures temperature by sensing a change in resistance as temperature changes. Temperature sensors are usually digital sensors the internally convert the resistance measured into a temperature in degrees Celsius (or Kelvin, or Fahrenheit).
|
|
|
|
### Add the sensors to CounterFit
|
|
|
|
To use a virtual humidity and temperature sensor, you need to add the two sensors to the CounterFit app
|
|
|
|
#### Task - add the sensors to CounterFit
|
|
|
|
Add the humidity and temperature sensors to the CounterFit app.
|
|
|
|
1. Create a new Python app on your computer in a folder called `temperature-sensor` with a single file called `app.py` and a Python virtual environment, and add the CounterFit pip packages.
|
|
|
|
> ⚠️ 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).
|
|
|
|
1. Install an additional Pip package to install a CounterFit shim for the DHT11 sensor. Make sure you are installing this from a terminal with the virtual environment activated.
|
|
|
|
```sh
|
|
pip install counterfit-shims-seeed-python-dht
|
|
```
|
|
|
|
1. Make sure the CounterFit web app is running
|
|
|
|
1. Create a humidity sensor:
|
|
|
|
1. In the *Create sensor* box in the *Sensors* pane, drop down the *Sensor type* box and select *Humidity*.
|
|
|
|
1. Leave the *Units* set to *Percentage*
|
|
|
|
1. Ensure the *Pin* is set to *5*
|
|
|
|
1. Select the **Add** button to create the humidity sensor on Pin 5
|
|
|
|
|
|
|
|
The humidity sensor will be created and appear in the sensors list.
|
|
|
|
|
|
|
|
1. Create a temperature sensor:
|
|
|
|
1. In the *Create sensor* box in the *Sensors* pane, drop down the *Sensor type* box and select *Temperature*.
|
|
|
|
1. Leave the *Units* set to *Celsius*
|
|
|
|
1. Ensure the *Pin* is set to *6*
|
|
|
|
1. Select the **Add** button to create the temperature sensor on Pin 6
|
|
|
|
|
|
|
|
The temperature sensor will be created and appear in the sensors list.
|
|
|
|
|
|
|
|
## Program the temperature sensor app
|
|
|
|
The temperature sensor app can now be programmed using the CounterFit sensors.
|
|
|
|
### Task - program the temperature sensor app
|
|
|
|
Program the temperature sensor app.
|
|
|
|
1. Make sure the `temperature-sensor` app is open in VS Code
|
|
|
|
1. Open the `app.py` file
|
|
|
|
1. Add the following code to the top of `app.py` to connect the app to CounterFit:
|
|
|
|
```python
|
|
from counterfit_connection import CounterFitConnection
|
|
CounterFitConnection.init('127.0.0.1', 5000)
|
|
```
|
|
|
|
1. Add the following code to the `app.py` file to import the required libraries:
|
|
|
|
```python
|
|
import time
|
|
from counterfit_shims_seeed_python_dht import DHT
|
|
```
|
|
|
|
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.
|
|
|
|
1. Add the following code after the code above to create an instance of the class that manages the virtual humidity and temperature sensor:
|
|
|
|
```python
|
|
sensor = DHT("11", 5)
|
|
```
|
|
|
|
This declares an instance of the `DHT` class that manages the virtual **D**igital **H**umidity and **T**emperature sensor. The first parameter tells the code the sensor being used is a virtual *DHT11* sensor. The second parameter tells the code the sensor is connected to port `5`.
|
|
|
|
> 💁 CounterFit simulates this combined humidity and temperature sensor by connecting to 2 sensors, a humidity sensor on the pin given 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 temperatures sensor to be on pin 6.
|
|
|
|
1. Add an infinite loop after the code above to poll the temperature sensor value and print it to the console:
|
|
|
|
```python
|
|
while True:
|
|
_, temp = sensor.read()
|
|
print(f'Temperature {temp}°C')
|
|
```
|
|
|
|
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.
|
|
|
|
1. Add a small sleep of ten seconds at the end of the `loop` as the temperature levels don't need to be checked continuously. A sleep reduces the power consumption of the device.
|
|
|
|
```python
|
|
time.sleep(10)
|
|
```
|
|
|
|
1. From the VS Code Terminal with an activated virtual environment, run the following to run your Python app:
|
|
|
|
```sh
|
|
python app.py
|
|
```
|
|
|
|
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:
|
|
|
|
* Enter a number in the *Value* box for the temperature sensor, then select the **Set** button. The number you enter will be the value returned by the sensor.
|
|
|
|
* Check the *Random* checkbox, and enter a *Min* and *Max* value, then select the **Set** button. Every time the sensor reads a value, it will read a random number between *Min* and *Max*.
|
|
|
|
You should see the values you set appearing in the console. Change the *Value* or the *Random* settings to see the value change.
|
|
|
|
```output
|
|
(.venv) ➜ temperature-sensor python app.py
|
|
Temperature 28.25°C
|
|
Temperature 30.71°C
|
|
Temperature 25.17°C
|
|
```
|
|
|
|
> 💁 You can find this code in the [code-temperature/virtual-device](code-temperature/virtual-device) folder.
|
|
|
|
😀 Your temperature sensor program was a success!
|