A simple python project for testing all the 16 sensors in order to see if they work well.
It all starts with a menu for choosing the sensor group that we want to test, it also demands in which channel did we connect the data pin, and then the code will output the sensor data for 1min whenever there is an event trigger by the sensor. The output is simple text to the terminal.
For this first commit only the sensors with simple digital output are covered.
- The 16 sensors covered / to cover
- Basic notions
- Code explanation
- Sensors table
- Sensors one by one
- Changelog
- DHT11 temperature and humidity sensor module
- HC-SR501 infrared human body induction module
DS1302 real time clock module- Rain sensor module
- Sound sensor module
- HC-SR04 ultrasonic sensor module
- Flame sensor module
KY-008 laser head sensor module- Photosensitive resistance sensor module
- VY-69 soil moisture sensor module
- Obstacle avoidance module
- Vibration sensor module
- MQ-2 gas sensor module
433M super regenerative module- Tilt sensor module
- Path tracing module
General Purpose Input Output
BCM - "Broadcom SOC channel" number, it will be different in some raspberry Pi versions.
BOARD - The numbers printed on the board.
Polling is the way of checking the input in a certain time, but it can miss an input if the program reads the value at the wrong time and consumes a lot of CPU.
Interrups occurs when there is a change in state of the input.
More info here.
1/High/3.3V or 0/LOW/0V
The digital input only returns 0 or 1, but the analog can returns a bigger interval of values, being perfect for example for the sound sensor where is possible to detect the intensity of the sound.
More info here.
The program is organised in 2 files, main.py and sensor_test.py, the first one runs the menu and calls the second one. The file sensor_test.py is where the code receives the data from the sensor.
To add the interrups in order to fire when there is an event:
GPIO.add_event_detect(channel, GPIO.BOTH, bouncetime=300)
GPIO.add_event_callback(channel, callback)
And when we finish using the GPIO pins, we remove the event detection and we make a cleanup to the GPIO pins.
GPIO.remove_event_detect(channel)
GPIO.cleanup()
First it’s necessary to have the build-essential and python-dev packages installed:
sudo apt-get update
sudo apt-get install build-essential python-dev
Second, we can clone the Adafruit library from the library repository:
git clone https://github.com/adafruit/Adafruit_Python_DHT.git
cd Adafruit_Python_DHT
And finally install the library in our system for python 2 and 3:
sudo python setup.py install
sudo python3 setup.py install
At this point the library will be installed and ready to be used.
| # | Sensor | Voltage | Extra | Analog Port | Digital Output |
|---|---|---|---|---|---|
| 1 | DHT11 temperature and humidity sensor module | 3.3V -5V | No | Lib needed | |
| 2 | HC-SR501 infrared human body induction module | 3.3V -5V | No | 0 / 1 | |
| 3 | DS1302 real time clock module | 3.3V | Yes | Different | |
| 4 | Rain sensor module | 3.3V -5V | Yes | 0 / 1 | |
| 5 | Sound sensor module | 5V | Yes | 0 / 1 | |
| 6 | HC-SR04 ultrasonic sensor module | 5V | Echo (reduce power) | No | 0 / 1 |
| 7 | Flame sensor module | 3.3V -5V | No | 0 / 1 | |
| 8 | KY-008 laser head sensor module | 5V | need laser receiver | No | 0 / 1 time |
| 9 | Photosensitive resistance sensor module | 3.3V -5V | No | 0 / 1 | |
| 10 | VY-69 soil moisture sensor module | 3.3V -5V | Yes | 0 / 1 | |
| 11 | Obstacle avoidance module | 3.3V -5V | No | 0 / 1 | |
| 12 | Vibration sensor module | 3.3V -5V | No | 0 / 1 | |
| 13 | MQ-2 gas sensor module | 5V | Yes | 0 / 1 | |
| 14 | 433M super regenerative module | 5V | 2 Data pins | No | Lib needed (Rpi) |
| 15 | Tilt sensor module | 3.3V -5V | No | 0 / 1 | |
| 16 | Path tracing module | 5V | No | 0 / 1 |
- The sensor 1 needs a special library in order to obtain the data.
- The sensors 2,4,5,6,7,9,10,11,12,13,15 and 16 they all have the same pattern, the output is either 1 or 0.
- The sensor 3 it’s a clock for store the time.
- The sensor 8 we can only turn it on or off, in order to make it more interesting is necessary a laser receiver, to know if an object has crossed the laser path.
- And finally the sensor 14, like the sensor 1 needs a special library in order to get the sensor data.
There are 2 DHT11, one with 3 pins and the other with 4 pins, the last one will require a resistor (10K) to be place between the pin 1 (3.3V) and the pin 2 (Data). The three pin DHT11 has already the resistor.
This sensor requires a specific protocol to be applied to the data pin, we can easily achieve that with the Adafruit DHT library.
It will return the temperature and humidity in ºC and %.
The Infrared sensor or PIR sensor can detect motion in a range from 3m to 7m and it's possible to adjust the delay time from 5s to 200s.
The rain sensor will output low level when it detects rain in the board. It's possible to calibrate the sensor potentiometer in order to trigger only when is has couple of drops or a really large one.
The sound sensor will output low level when a sound is detected. Important note: Some modules are complitly off tuned, it's necessary to adjust the potentiometer, conter clockwise will reduce the sensitivity, the equilibrium point is when 1 of the 2 leds turns off.
Important: The sensor output signal (ECHO) is rated 5V, but the input pin on the Raspberry Pi GPIO is rated 3.3V. Sending a 5V signal to the GPIO could damage it. It's necessary to use a small voltage divider circuit, consisting of two resistors, to lower the sensor output voltage to something that the Raspberry Pi can handle.
This sensor detects a flame or a light source, with a wavelengh from 700nm to 1000nm, the sensitive can be ajustable.
This sensor can detect the ambient brightness and light intensity.
#####How it works
The infrared transmitter on the sensor emits rays, if it touch a black surface it will absorbed and the sensor will output high level (1), else, it will output low level (0).
Version 1.0 - 12/06/2018
- Base code for the first sensors
Ivo Lopes aka Charro 2018