Raspberry Pi Forums

pirx1988 wrote: ↑

Tue Jun 09, 2020 2:23 pm

Hi, I have created simple light dector. Schemea is below:


Real circuit on breadboard:



I have written code in python using GPIO library:

Code: Select all

import signal
import sys
import RPi.GPIO as GPIO
import sqlite3
import datetime
INPUT_GPIO = 16
def save_light_event_in_db():
    try:
        conn = sqlite3.connect('/home/pi/databases/light_sensor.db')
        cur = conn.cursor()
        cur.execute('SELECT * from light_events')
        light_time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
        message = "Wykryto świt!"
        sqlite_insert_with_param = """INSERT INTO light_events
                              (created_at, message)
                              VALUES (?, ?);"""
        data_tuple = (light_time, message)
        cur.execute(sqlite_insert_with_param, data_tuple)
        conn.commit()
    except Error as e:
            print(e)
    finally:
       if conn:
           conn.close()

def signal_handler(sig, frame):
    GPIO.cleanup()
    sys.exit(0)
def light_detection_callback(channel):
    print("Yeah, juz swita, wstawać!")
    save_light_event_in_db()
    
if __name__ == '__main__':
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(INPUT_GPIO, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    GPIO.add_event_detect(INPUT_GPIO, GPIO.FALLING, 
            callback=light_detection_callback, bouncetime=1000) 
    signal.signal(signal.SIGINT, signal_handler)
    signal.pause()

This circuit should detect only situation when light has changed from night to dawn. I have configured pull up resistor on board and I've used and GL5539, which has light resistance in range 50-10k, and dark resistance 5 mega ohm. The problem is, it records also events with. twilight I don't know wy. Where is a problem?
I would be grateful for explanation, some advices.
Best regards

drgeoff wrote: ↑

Wed Jun 10, 2020 11:34 am

Agreed that the 100k resistor should be adjusted. However, no need for "protection" as even if zero ohms is there, nothing will be damaged.