Objective of this project:
There are barriers between a railroad train and a pedestrian or car crossing.
In this project we will realize a system that simulate the operation of automatic barriers for railways trains.
We will design this system using:
- ESP32 card
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two ultrasonic sensors hc-sr04 for the detection of the arrival of the train.
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two servomotors to lower or raise the barriers
Operation of the barrier controlled by ESP32:
Components required
- ESP32 card
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HC-SR04 sensor
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Supply power module
- LEDs
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test plate
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connecting wires
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toy train
Mounting:
To do the assembly, we connected:
For the first sound sensor HC-SR04:
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the VCC pin to the 3.3V pin of ESP32
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the Trig pin to pin D5 of ESP32
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the ECHO pin to pin D18 of ESP32
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the GND pin to the GND pin of ESP32
For the second sound sensor HC-SR04:
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the VCC pin to the 3.3V pin of ESP32
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the Trig pin to pin D22 of ESP32
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the ECHO pin to pin D23 of ESP32
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the GND pin to the GND pin of ESP32
For the first servomotor:
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red wire: power supply wire to be connected to the 5V terminal of the power supply module
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brown wire: wire to connect to the GND pin of ESP32
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Yellow: Positioning signal wire connected to pin D4 of ESP32
For the second servomotor:
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red wire: power supply wire to be connected to the 5V terminal of the power supply module
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brown wire: wire to connect to the GND pin of ESP32
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Yellow: Positioning signal wire connected to pin D21 of ESP32
For LEDs:
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the terminals (-) of the LEDs to GND of ESP32
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the (+) terminal of the first red LED to pin D2 of ESP32
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the (+) terminal of the second red LED to pin D19 of ESP32
Micropython programs
Here are the micropython programs that allow you to:
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calculate the distance between the HC-SR04 sensor and the detected object
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raise or lower barriers
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turn LEDs on or off
esp32-barrieres.py:
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import machine from hcsr04 import HCSR04 from machine import Pin from servo import Servo import utime sensor1 = HCSR04(trigger_pin=5,echo_pin=18,echo_timeout_us=1000000) sensor2 = HCSR04(trigger_pin=22,echo_pin=23,echo_timeout_us=1000000) servo1_pin = machine.Pin(4) servo2_pin = machine.Pin(21) my_servo1 = Servo(servo1_pin) my_servo2 = Servo(servo2_pin) led1=Pin(2,Pin.OUT) led2=Pin(19,Pin.OUT) i1=90 i2=90 while True: distance1 = sensor1.distance_cm() distance2 = sensor2.distance_cm() if distance1<4 and distance1>0: # If the hc-sr04 sensor detects the arrival of the train while i1 > 0: led1.value(1) # Turn on the red LED my_servo1.write_angle(i1) # lower the barrier utime.sleep_ms(10) i1-=1 else: # Absent from train while i1 < 90: led1.value(0) # Turn off the red LED my_servo1.write_angle(i1) # raise the barrier utime.sleep_ms(10) i1+=1 if distance2<4 and distance2>0: # If hc-sr04 sensor detects detecte the arrival of train while i2 > 0: led2.value(1) # Turn on the red LED my_servo2.write_angle(i2)# lower the barrier utime.sleep_ms(10) i2-=1 else: # en absent the train while i2 < 90: led2.value(0)# Turn off the red LED my_servo2.write_angle(i2) # raise the barrier utime.sleep_ms(10) i2+=1 |
servo.py
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from machine import PWM import math # originally by Radomir Dopieralski http://sheep.art.pl # from https://bitbucket.org/thesheep/micropython-servo class Servo: """ A simple class for controlling hobby servos. Args: pin (machine.Pin): The pin where servo is connected. Must support PWM. freq (int): The frequency of the signal, in hertz. min_us (int): The minimum signal length supported by the servo. max_us (int): The maximum signal length supported by the servo. angle (int): The angle between the minimum and maximum positions. """ def __init__(self, pin, freq=50, min_us=600, max_us=2400, angle=180): self.min_us = min_us self.max_us = max_us self.us = 0 self.freq = freq self.angle = angle self.pwm = PWM(pin, freq=freq, duty=0) def write_us(self, us): """Set the signal to be ``us`` microseconds long. Zero disables it.""" if us == 0: self.pwm.duty(0) return us = min(self.max_us, max(self.min_us, us)) duty = us * 1024 * self.freq // 1000000 self.pwm.duty(duty) def write_angle(self, degrees=None, radians=None): """Move to the specified angle in ``degrees`` or ``radians``.""" if degrees is None: degrees = math.degrees(radians) degrees = degrees % 360 total_range = self.max_us - self.min_us us = self.min_us + total_range * degrees // self.angle self.write_us(us) |
hc-sr04.py:
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import machine, time from machine import Pin __version__ = '0.2.0' __author__ = 'Roberto S鐠嬶箯chez' __license__ = "Apache License 2.0. https://www.apache.org/licenses/LICENSE-2.0" class HCSR04: """ Driver to use the untrasonic sensor HC-SR04. The sensor range is between 2cm and 4m. The timeouts received listening to echo pin are converted to OSError('Out of range') """ # echo_timeout_us is based in chip range limit (400cm) def __init__(self, trigger_pin, echo_pin, echo_timeout_us=500*2*30): """ trigger_pin: Output pin to send pulses echo_pin: Readonly pin to measure the distance. The pin should be protected with 1k resistor echo_timeout_us: Timeout in microseconds to listen to echo pin. By default is based in sensor limit range (4m) """ self.echo_timeout_us = echo_timeout_us # Init trigger pin (out) self.trigger = Pin(trigger_pin, mode=Pin.OUT, pull=None) self.trigger.value(0) # Init echo pin (in) self.echo = Pin(echo_pin, mode=Pin.IN, pull=None) def _send_pulse_and_wait(self): """ Send the pulse to trigger and listen on echo pin. We use the method `machine.time_pulse_us()` to get the microseconds until the echo is received. """ self.trigger.value(0) # Stabilize the sensor time.sleep_us(5) self.trigger.value(1) # Send a 10us pulse. time.sleep_us(10) self.trigger.value(0) try: pulse_time = machine.time_pulse_us(self.echo, 1, self.echo_timeout_us) return pulse_time except OSError as ex: if ex.args[0] == 110: # 110 = ETIMEDOUT raise OSError('Out of range') raise ex def distance_mm(self): """ Get the distance in milimeters without floating point operations. """ pulse_time = self._send_pulse_and_wait() # To calculate the distance we get the pulse_time and divide it by 2 # (the pulse walk the distance twice) and by 29.1 becasue # the sound speed on air (343.2 m/s), that It's equivalent to # 0.34320 mm/us that is 1mm each 2.91us # pulse_time // 2 // 2.91 -> pulse_time // 5.82 -> pulse_time * 100 // 582 mm = pulse_time * 100 // 582 return mm def distance_cm(self): """ Get the distance in centimeters with floating point operations. It returns a float """ pulse_time = self._send_pulse_and_wait() # To calculate the distance we get the pulse_time and divide it by 2 # (the pulse walk the distance twice) and by 29.1 becasue # the sound speed on air (343.2 m/s), that It's equivalent to # 0.034320 cm/us that is 1cm each 29.1us cms = (pulse_time / 2) / 29.1 return cms |
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