readme.md

For the following layout, where squares are sensors that send a signal when the train passes and circles are switches. The train only goes counter clockwise in the big oval.

model_railway.py

import RPi.GPIO as GPIO
from random import randrange
from time import sleep
import threading

# Set the time for the relays to be turned on, before being turned off again
SWITCH_TIME = 0.1

GPIO.setmode(GPIO.BCM)

# input sensor hill
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

# input sensor tunnel
GPIO.setup(27, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

# switch group A
GPIO.setup(13, GPIO.OUT)
GPIO.setup(16, GPIO.OUT)

# switch b
GPIO.setup(19, GPIO.OUT)
GPIO.setup(20, GPIO.OUT)

# switch c
GPIO.setup(26, GPIO.OUT)
GPIO.setup(21, GPIO.OUT)

# Enable AC Power
GPIO.setup(2, GPIO.OUT)
GPIO.output(2, GPIO.LOW)

switch_lock = threading.Lock()

switch_status = {
    'a': None,
    'b': None,
    'c': None
}


def station_entry(*args):
    print('Entering the Station!')
    direction = 13
    if randrange(0, 10) < 5:
i        direction = 16

    with switch_lock:
        if switch_status['a'] != direction:
            switch_status['a'] = direction
            GPIO.output(direction, GPIO.HIGH)

        if switch_status['c'] != 26:
            switch_status['c'] = 26
            GPIO.output(26, GPIO.HIGH)

        if randrange(0, 10) < 4:
            switch_status['b'] = 19
        else:
            switch_status['b'] = 20

        sleep(SWITCH_TIME)
        GPIO.output(direction, GPIO.LOW)
        GPIO.output(26, GPIO.LOW)
        print(switch_status)


def bridge_crossing(*args):
    print('Crossing the Bridge!')
    direction = 19
    if randrange(0, 10) < 3:
        direction = 20

    with switch_lock:
        if switch_status['b'] != direction:
            switch_status['b'] = direction
            GPIO.output(direction, GPIO.HIGH)

        if switch_status['c'] != 21:
            switch_status['c'] = 21
            GPIO.output(21, GPIO.HIGH)

        sleep(SWITCH_TIME)
        GPIO.output(direction, GPIO.LOW)
        GPIO.output(21, GPIO.LOW)
        print(switch_status)


print('Setup completed!')
print(switch_status)
print()
GPIO.add_event_detect(27, GPIO.RISING, callback=bridge_crossing, bouncetime=1000)
GPIO.add_event_detect(17, GPIO.RISING, callback=station_entry, bouncetime=1000)