Add 6 Ultrasonic Distance Sensors to Existing Raspberry Pi Robot

This is NOT a tutorial to make a Raspberry Pi robot with 6 Ultrasonic Sensors.

This is a tutorial shows the best method to add 6 Ultrasonic Sensors directly to a raspberry pi without the use of any micro controller like Arduino.

LEVEL: ADVANCED

Prerequisite:

• I would be referring to Ultrasonic Sensors as USS in short.
• All +5v, +3v and GND pins need to be connected to a +5v, +3v or GND rail respectively.

The Raspberry Pi's GPIO work on 3.3v and USS works on 5v, although we can always use resistor to limit current, Bi-Directions Level converters are a much more elegant solution.

Hardware Requirements:

• 6x HC-SR04 USS (Click Here)
• 6x USS Brackets (Click Here)
• 3x Bi directional Level Shifters - Make sure they are I2C safe (Click Here)
• Bunch of Famale to Femal Jumper Cables (Click Here)
• Raspberry pi Robot

Software Setup:

• sudo apt-get install pigpio

Example connection on the Bi-Directional Level Shifter

LV	+3.3V
HV	+5V
L1	GPIO Pin of your choice for trigger1
H1	Trig Pin On USS1
L2	GPIO Pin of your choice for ECHO1
H2           ECHO Pin On USS2
L3           GPIO Pin of your choice for trigger2
H3	Trig Pin On USS2
L4	GPIO Pin of your choice for ECHO2
H4      ECHO Pin On USS2
GND	GND Rail

Example connection on the USS

VCC	+5v
GND	GND Rail
Trigg	H1 Level Shifter
Echo	H2 Level Shifter

As you can see we have two USS using one same Level shifter so for 6 USS we have 3 Level Shifters.

You can refer to this document for connecting the USS through Level Shifter to the Raspberry Pi (Click Here)

This is the Python code i use to run all the 6 USS

As you can see Memcached can also be use to extract values from this script.

This scrip works on the pins as mentioned in the example document provided in the previous step, pin numbers need to be edited specifically.

#!/usr/bin/env python
#
# HC-SR04 interface code for the Raspberry Pi
#
# William Henning @  http://Mikronauts.com

#
# uses joan's excellent pigpio library
#
# Does not quite work in one pin mode, will be updated in the future
#
import time
import pigpio
#import memcache
#mc = memcache.Client(['127.0.0.1:11211'], debug=0)
def _echo1(gpio, level, tick):
   global _high
   _high = tick
def _echo0(gpio, level, tick):
   global _done, _high, _time
   _time = tick - _high
   _done = True
def readDistance2(_trig, _echo):
   global pi, _done, _time
   _done = False
   pi.set_mode(_trig, pigpio.OUTPUT)
   pi.gpio_trigger(_trig,50,1)
   pi.set_mode(_echo, pigpio.INPUT)
   time.sleep(0.0001)
   tim = 0
   while not _done:
      time.sleep(0.001)
      tim = tim+1
      if tim > 50:
         return 2900
   return _time
pi = pigpio.pi('localhost',1234)
if __name__ == "__main__":
   my_echo1 = pi.callback(10, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(10, pigpio.FALLING_EDGE, _echo0)
   my_echo1 = pi.callback(25, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(25, pigpio.FALLING_EDGE, _echo0)
   my_echo1 = pi.callback(8, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(8, pigpio.FALLING_EDGE, _echo0)
   my_echo1 = pi.callback(5, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(5, pigpio.FALLING_EDGE, _echo0)
   my_echo1 = pi.callback(12, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(12, pigpio.FALLING_EDGE, _echo0)
   my_echo1 = pi.callback(16, pigpio.RISING_EDGE,  _echo1)
   my_echo0 = pi.callback(16, pigpio.FALLING_EDGE, _echo0)
   while 1:
      print "DISTANCE 1: ",(readDistance2(24,10)/58)
      print "DISTANCE 2: ",(readDistance2(9,25)/58)
      print "DISTANCE 3: ",(readDistance2(11,8)/58)
      print "DISTANCE 4: ",(readDistance2(7,5)/58)
      print "DISTANCE 5: ",(readDistance2(6,12)/58)
      print "DISTANCE 6: ",(readDistance2(19,16)/58)
      #mc.set("d1",(readDistance2(24,10)/58))
      #mc.set("d2",(readDistance2(9,25)/58))
      #mc.set("d3",(readDistance2(11,8)/58))
      #mc.set("d4",(readDistance2(7,5)/58))
      #mc.set("d5",(readDistance2(6,12)/58))
      #mc.set("d6",(readDistance2(19,16)/58))
      time.sleep(0.05)
#   my_echo1.cancel()
#   my_echo0.cancel()