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I'm currently using an mq5 gas sensor in my kitchen with the MCP3208 ADC. my code shows a continuous loop of the voltage charge. in the mq5 as it detects gases in the air. It is supposed to print ("Gas leak") on line 9 when the voltage reaches the set threshold of 0.50 but it does not. Am i doing something wrong?

#main loop
def main():
     init()
     while True:
              smokelevel=readadc(smokesensor_apin, SPICLK, SPIMOSI, SPIMISO, SPICS)

              if GPIO.input(smokesensor_dpin)> 0.50 :
                       if GPIO.input(smokesensor_dpin) > 0.50 :
                           print("Gas leak")

              else:
                       print("Gas lealage")
                       print"Current Gas AD vaule = " +str("%.2f"%((smokelevel/1024.)*5))+" V"
                       time.sleep(0.5)

if __name__ =='__main__':
     try:
              main()
              pass
     except KeyboardInterrupt:
              pass
  • i think that GPIO.input will return a digital value, ie a one or zero and am confused as to how you plan on comparing that to 0.50 – Mohammad Ali Sep 10 '17 at 18:27
  • ok yes, i understand the digital usage of the pins...what i actually need the code to do is tell the analog to digital converter to alert me when the voltage on the sensor exceeds a threshold. – Allen Jakpa Sep 10 '17 at 23:57
  • pretty sure you're going to need to look up the spec sheet for your adc. their are many tutorials online for this: learn.adafruit.com/raspberry-pi-analog-to-digital-converters/… – Mohammad Ali Sep 10 '17 at 23:59
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Code snippets are rarely conclusive. We have to guess at the missing parts.

All the Pi's GPIO are digital. They return 0 or 1, which is what I guess your GPIO.input() function is doing.

  • Would it help if I post the full code here ? – Allen Jakpa Sep 20 '17 at 19:05
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If you want to interface MQ sensors with raspbery pi you will need a analog to digital converter, on you can buy a breakout board whihc has MQ sensor and ADC on the same board like this one You can use this python script to read MQ5 gas sensor.

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