BH1750 always give 0 lx

[Luca Albano]

Hi,
I have a problem with BH1750 light sensor.
It is inside a sensorial node and communicate with LoPy by I2C bus.
In the first cicle, i have a correct measure, for example (light is the first value: 79):

79;22.0;63.5;1017.7;17;25;32;82;2021-02-17 10:53:55

From 2nd, i have always 0.
This is the code:

from sht10 import SHT10
from machine import Pin
import time
import pycom
import struct
import math
import bh1750fvi
import bme680
from i2c import I2CAdapter
from hm3301 import HM3301
from network import Sigfox
import socket
import utime
from machine import I2C
import machine
from network import WLAN
from machine import RTC
from machine import SD
import os
import sys

pycom.heartbeat(False) # disable the blue blinking

# ____ SD _____
try:
    sd = SD()
    os.mount(sd, '/sd')

    # check the content
    os.listdir('/sd')
    # f = open('/sd/data.csv', 'w')
except:
    print("Error: no SD")
    sys.exit(1)

# ____ WiFi connession _____
# configure the WLAN subsystem in station mode (the default is AP)
print("Configuring WLAN...")
wlan = WLAN(mode=WLAN.STA)
# go for fixed IP settings (IP, Subnet, Gateway, DNS)
wlan.ifconfig(config=('192.168.1.107', '255.255.255.0', '192.168.1.1', '192.168.1.1'))
wlan.scan()     # scan for available networks
wlan.connect(ssid='*********', auth=(WLAN.WPA2, '*********'))
while not wlan.isconnected():
    pass
print(wlan.ifconfig())
time.sleep(5)

# ____ Update time _____
print("Update time...")
rtc = RTC()
rtc.ntp_sync("it.pool.ntp.org")

data_pin = 'P9'
sck_pin = 'P10'

p_out_light = Pin('P20', mode=Pin.OUT)
p_out_light.value(1)
time.sleep(1)

#i2c_var = I2CAdapter(pins=(data_pin, sck_pin))
i2c=I2C(0, I2C.MASTER)
i2c.scan()

#print(i2c_var.scan())

p_out_light.value(0) # Pin off

try:
    while True:
        f = open('/sd/data.csv', 'a')

        date = rtc.now()

        p_out_light.value(1)
        print("---- PIN ON ----")
        time.sleep(1)

        pycom.rgbled(0xFFA500)
        time.sleep(0.5)
        pycom.rgbled(0x000000)
        time.sleep(0.5)
        pycom.rgbled(0xFFA500)
        time.sleep(0.5)
        pycom.rgbled(0x000000)
        time.sleep(0.5)
        pycom.rgbled(0xFFA500)
        time.sleep(0.5)
        pycom.rgbled(0x000000)
        time.sleep(0.5)
        pycom.rgbled(0xFFA500)
        time.sleep(0.5)
        pycom.rgbled(0x000000)
        time.sleep(0.5)

        print("Measuring...")
        output = ""

        # Luminosità
        i2c_var = I2CAdapter(pins=(data_pin, sck_pin))
        #i2c_var.writeto(i2c_var.scan()[0], bytes([0x10]))
        light_sensor = bh1750fvi.BH1750FVI(i2c_var)
        # print("LUX:")
        print(i2c_var.scan()[0])
        lux = light_sensor.read()
        i2c_var.writeto(i2c_var.scan()[0], bytes([0x10]))
        #print(lux)
        output = str(lux) + ";"
        time.sleep(1)
        #time.sleep(1)

        # Temperatura
        sht = SHT10(data_pin, sck_pin)
        tmp = sht.readTemp()
        hum = sht.readHum()
        output += "{:.1f};{:.1f};".format(round(tmp,1), round(hum,1))
        time.sleep(1)

        # Pressione
        i2c_dev = I2CAdapter(pins=(data_pin, sck_pin))
        # print("PRESSION:")
        print(i2c_dev.scan()[1])
        # dev_add = i2c_dev.findSlaves()
        # print(dev_add)
        sensor = bme680.BME680(i2c_device=i2c_dev, i2c_addr=i2c_dev.scan()[1]) # se da errore "index out of range", cambiare da 1 a 0, poi da 0 ad 1 e ricaricare 4-5 volte
        sensor.set_pressure_oversample(bme680.OS_4X)
        sensor.set_filter(bme680.FILTER_SIZE_3)
        if sensor.get_sensor_data():
            output += "{:.1f};".format(round(sensor.data.pressure,1))
        time.sleep(1)

        # PM
        time.sleep(1)
        hm = HM3301('P21', 'P22') # P21 -> data , P22 -> clock
        #hm.findSlaves()
        pm1 = hm.readStandardPM()
        dep_string = ""
        pm_index_count = 0 # indice per PM
        c_pm1 = 0
        c_pm10 = 0
        c_pm25 = 0
        for digit in pm1:
            pm_index_count += 1

            if pm_index_count == 1:
                c_pm1 = digit
            elif pm_index_count == 2:
                c_pm25 = digit
            elif pm_index_count == 3:
                c_pm10 = digit
        time.sleep(1)
        pm2 = hm.readAtmosphericPM()
        dep_string = ""
        pm_index_count = 0 # indice per PM
        c_pm1atm = 0
        c_pm10atm = 0
        c_pm25atm = 0
        for digit in pm2:
            pm_index_count += 1
            if pm_index_count == 1:
                c_pm1atm = digit
            elif pm_index_count == 2:
                c_pm25atm = digit
            elif pm_index_count == 3:
                c_pm10atm = digit
        time.sleep(1)

        # Media tra valori PM std e PM atm
        c_pm1_fin =  (c_pm1 + c_pm1atm) / 2
        c_pm10_fin = (c_pm10 + c_pm10atm) / 2
        c_pm25_fin = (c_pm25 + c_pm25atm) / 2

        output += str(round(c_pm1_fin)) + ";" + str(round(c_pm25_fin)) + ";" + str(round(c_pm10_fin)) + ";"

        vl_pm10 = 50 # limite giornaliero PM10 -> è 50 per la legge italiana
        vl_pm25 = 25 # limite giornaliero PM2.5

        # PM1 -> NON é POSSIBILE INSERIRLI PERCHé NON C'é UN LIMITE GIORNALIERO MESSO PER LEGGE

        # sottoindici
        i_pm10 = (c_pm10_fin / vl_pm10) * 100
        i_pm25 = (c_pm25_fin / vl_pm25) * 100

        index_pm = round((i_pm10 + i_pm25) / 2)

        if index_pm >= 0 and index_pm <= 50:
            dep_pm = 1 # "OTTIMA"
        elif index_pm > 50 and index_pm <= 75:
            dep_pm = 2 # "BUONA"
        elif index_pm > 75 and index_pm <= 100:
            dep_pm = 3 # "DISCRETA"
        elif index_pm > 100 and index_pm <= 125:
            dep_pm = 4 # "MEDIOCRE"
        elif index_pm > 125 and index_pm <= 150:
            dep_pm = 5 # "POCO SALUBRE"
        elif index_pm > 150 and index_pm <= 175:
            dep_pm = 6 # "INSALUBRE"
        elif index_pm > 175:
            dep_pm = 7 # "MOLTO INSALUBRE"

        # init Sigfox for RCZ1 (Europe)
        print("Init SigFox...")
        sigfox = Sigfox(mode=Sigfox.SIGFOX, rcz=Sigfox.RCZ1)
        # create a Sigfox socket
        s = socket.socket(socket.AF_SIGFOX, socket.SOCK_RAW)
        # make the socket blocking
        s.setblocking(True)
        # configure it as uplink only
        s.setsockopt(socket.SOL_SIGFOX, socket.SO_RX, False)

        # send AQI
        my_string = str(round(tmp))+";"+str(round(hum))+";"+str(dep_pm)
        my_bytes = my_string.encode('utf-8')
        s.send(my_bytes)
        time.sleep(5)

        time.sleep(1)
        pycom.rgbled(0x2eff00)
        time.sleep(1)
        pycom.rgbled(0x000000)
        time.sleep(1)

        output += str(index_pm) + ";"
        dateUTC = '{:02d}-{:02d}-{:02d} {:02d}:{:02d}:{:02d}'.format(date[0],date[1],date[2],date[3],date[4],date[5])
        output += str(dateUTC) #timestamp

        print(output)

        # try some standard file operations
        f.seek(0, 2) # seek to end
        f.write(output+"\r\n")
        f.close()

        p_out_light.value(0)
        print("---- PIN OFF ----\n\n")

        index_time = 1 #600 # effettuo 6 misurazioni all'ora, 1 ogni 10 min
        while(index_time > 0):
            if index_time % 2:
                pycom.rgbled(0x4F3394)
            else:
                pycom.rgbled(0x000000)
            time.sleep(1)
            index_time = index_time - 1

        pycom.rgbled(0x000000)

        s.close()

        time.sleep(1)

except KeyboardInterrupt:
    print("\n---- END POLLING ----\n")
    f.close()
    pass

I have found something similar in forum (here) but i don't know how to solve this problem.

Sorry for my english!
Thanks a lot.

[Matthew Felgate 0]

Can you try reading the sensor twice?
(and throw away the first result)

light_sensor_temp = bh1750fvi.BH1750FVI(i2c_var)
light_sensor = bh1750fvi.BH1750FVI(i2c_var)

[Luca Albano]

@Matthew-Felgate-0 I have tried but this is the ouput:

Configuring WLAN...
('192.168.1.107', '255.255.255.0', '192.168.1.1', '192.168.1.1')
Update time...
---- PIN ON ----
Measuring...
35
119
Init SigFox...
205;21.2;62.8;1016.0;19;28;33;89;2021-02-17 15:22:11
---- PIN OFF ----


---- PIN ON ----
Measuring...
35
119
Init SigFox...
0;21.2;62.7;1016.0;16;24;28;74;2021-02-17 15:22:44
---- PIN OFF ----


---- PIN ON ----
Measuring...
35
119
Init SigFox...
0;21.2;62.9;1015.9;28;38;42;116;2021-02-17 15:23:16
---- PIN OFF ----

It doesn't work correctly

[livius]

@Luca-Albano
Did you tried on different pins then P9 and P10?
And how this sensor behave if you have only import releated to i2c and all otheres devicess are not connected?
I meen simple code without sd card, wifi, .....
I ask because for me it is working without any problems form months

[Luca Albano]

@livius Thanks for reply.
I tried this sensor in single in another shield (Arduino UNO) and there was always this problem.
I could try with P21 and P22 which I am already using for the PM sensor, but for me this is not an I2C bus problem ...

[livius]

If you have tried this sensor with different hardware and still problem occurs then probably some problem with sensor itself.
I use this sensor long long time and i have not any problems.

[Luca Albano]

@livius I probably damaged it: yesterday, for a second, I connected GND and Vcc by reversing them. Since then, the sensor has worked like this. The only way, i think, is trying with another BH1750 to verificate if it is damaged or not, do you think?

[livius]

@Luca-Albano
for me it looks like a fastest way to werify

[rcolistete]

I suggest anoter light sensor, MAX44009, better than BH1750 : low power (about 1 uA), "ultra-wide 22-bit dynamic range from 0.045 lux to 188,000 lux", etc.

[Luca Albano]

@rcolistete Thank you but for this thesis' project i have only this type of sensor.
I'll remember it!