Code to detect motion on Raspberry Pi with Miniature Reflective Infrared Optical Sensors - ITR20001/T from Adafruit https://www.adafruit.com/product/3930

ir-optical-sensor-pi

import logging
import datetime
from time import sleep
from gpiozero import MotionSensor


pir = MotionSensor(4, pull_up=True, sample_rate=200, threshold=0.2)

logging.basicConfig(filename='optical-sensor.log',level=logging.DEBUG)
datetime_set = False
motion_counter = 0

if __name__ == '__main__':
  logging.info("Date: " + datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S"))
  logging.info("Start Optical Sensor Pin " + str(pir.pin))
  while True:
    try:
      pir.wait_for_motion()
      if (pir.motion_detected):
        datetime_set = True
      else:
        datetime_set = False

      if (datetime_set):
        logging.info("Motion captured: " + datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S"))
        sleep(0.1)

    except KeyboardInterrupt:
      print("Quit")
      break