Grove Base Kit for Raspberry Pi - Lesson 5: Ultrasonic distance sensor and transmitter

Lesson 5: Ultrasonic distance sensor and relay

Objective

In this lesson we will use the Grove - ultrasonic distance sensor to measure the distance when someone comes close, the light on the Grove - relay should switch on.

Hardware requirement

Prepare:

  • microUSB cable
  • Raspberry Pi
  • Computer

Included in the set

  • Grove Base Hat
  • Grove wire
  • Grove - Ultrasonic distance sensor
  • Grove - Relay

Connecting equipment

Step 1 Connect Grove - Ultrasonic distance sensor to port D5, Grove - Relay to port D16 on Base Hat.

Step 2 Connect Base Hat to Raspberry Pi

Step 3 Connect the Raspberry Pi to the power source using the microUSB cable.

Programming

Note

Make sure you clone the python.py repository library on your Raspberry Pi.

Step 1: Enter the following commands to create a Python file

  1. cd grove.py
  2. nano lesson_5.py

Step 2: Copy the following code

  1. #!/usr/bin/env python
  2.  
  3. import time
  4.  
  5. from grove.grove_relay import GroveRelay
  6. from grove.grove_ultrasonic_ranger import GroveUltrasonicRanger
  7.  
  8. def main():
  9.     # Grove - Ultrasonic Ranger connected to port D5
  10.     sensor = GroveUltrasonicRanger(5)
  11.  
  12.     # Grove - Relay connected to port D16
  13.     relay = GroveRelay(16)
  14.  
  15.     while True:
  16.         distance = sensor.get_distance()
  17.         print('{} cm'.format(distance))
  18.  
  19.         if distance < 20:
  20.             relay.on()
  21.             print('relay on')
  22.  
  23.             time.sleep(1)
  24.  
  25.             relay.off()
  26.             print('relay off')
  27.  
  28.             continue
  29.  
  30.         time.sleep(1)
  31.  
  32. if __name__ === '__main__':
  33.     main()

Step 3：Uruchomprogram

  1. sudo chmod +x lesson_5.py
  2. sudo ./lesson_5.py

If everything goes well, a change in light intensity should cause a change in the angle of rotation of the servo.

  1. pi@raspberrypi:~/grove.py $ sudo ./lesson_5.py
  2. 253.722585481 cm
  3. 253.739028141 cm
  4. 252.896341784 cm
  5. 1.20442489098 cm
  6. relay on
  7. relay off
  8. 4.51762100746 cm
  9. relay on
  10. relay off
  11. 253.985668051 cm
  12. ^CTraceback (most recent call last):
  13.   File "./lesson_5.py", line 34, in 
  14.     main()
  15.   File "./lesson_5.py", line 31, in main
  16.     time.sleep(1)
  17. KeyboardInterrupt
  18. pi@raspberrypi:~/grove.py $

Now compare your results from the fourth and fifth lessons. Can you list the advantages and disadvantages of Grove - a mini PIR motion detector and Grove ultrasonic distance sensor?

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