Problems with SHT11 sensor

Comments

• Tracy Allen Posts: 6,667

  2006-10-01 04:25 edited 2006-10-01 04:25

  Did you purchase the SHT11 module from Parallax? Note that the pin numbers on the Parallax module are not the same as the pin numbers in the Sensirion documentation. Be sure to include the pulldown resistor on the sck line.
  
  What code are you using? Post it here or give us a reference. If there is a raw result value that comes back, it can sometimes help if you insert a DEBUG statement for that in the program. That helps to isolate the problem to before or after the computations.
  
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  Tracy Allen
  www.emesystems.com
• Sean11 Posts: 3

  2006-10-01 18:27 edited 2006-10-01 18:27

  Yes i did purchase the SHT11 from parallax
  The link below will show you the code and how the sensor is wired.
  http://www.parallax.com/dl/docs/prod/acc/SensirionDocs.pdf
  
  I am not familiar with PBasic what do you mean by enter a DEBUG statement
  thanks
• Franklin Posts: 4,747

  2006-10-01 21:11 edited 2006-10-01 21:11

  Sean, the program you referenced is full of debug statements. Did you load and run the program>
  
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  - Stephen
• Sean11 Posts: 3

  2006-10-01 23:00 edited 2006-10-01 23:00

  yes
• Tracy Allen Posts: 6,667

  2006-10-02 19:38 edited 2006-10-02 19:38

  Sean, is it the program that is listed in the file that you referenced, and did you type the program yourself, or did you copy and paste or download it from the web site?
  
  By DEBUG for the raw values, I am looking at this subroutine in the program listed in the pdf:
  
  

  SHT_Read_Byte:    
    SHIFTIN  ShtData, Clock, MSBPre, [noparse][[/noparse]ioByte]     ' get byte    
    SHIFTOUT ShtData, Clock, LSBFirst, [noparse][[/noparse]ackBit\1] ' send ack bit    
    INPUT ShtData                                 ' release data line 
    DEBUG ? iobyte      ' <------ADDED THIS DEBUG
    RETURN
  

  
  
  
  That should display raw iobytes on your screen along with calculated values. What do you see? At that point you will take the raw values and calculate temperature and humidity and compare results with the ones that the stamp has calculated. If they are different, you look at the code, if they are the same (and boh wrong), then you look at the hardware connection and the low level acquisition routine.
  
  The main thing is for you to understand how the chip and the program work!
  
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  Tracy Allen
  www.emesystems.com