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Member Since: May 19, 2010

Country: United States

  • A few tips on this device:
    - you only need I2C once to read 2 values from eeprom; you can make those values constants in code and disconnect i2c
    - eeprom values (sens and offset) are stored with MSB first (ex: sens is a 2 byte value, addr 10 is MSB and addr 11 is LSB)
    - sens should be appx 300-400, offset appx 7500-7700
    - only 3 pins are needed to read values (vdd, gnd, fout), fout outputs pulses representing a frequency 5-10khz, you must count the rising edges to calculate freq
    - I could not get accurate readings using a 6" jumper wire, I had to solder a pin to fout and plug in directly at mcu
    - here is an example of my eeprom values along with a sample fout reading and the calculation to get RH:
    eeprom sens: 405
    eeprom offset: 7504 (the value in eeprom is in hz)
    sample fout rising edge count in 1 second: 7335 (i.e. 7335 hz)
    plugged into the calculation from datasheet:
    (7504-7335)*405/4096 = %16.71 relative humidity, which I confirmed with a different sensor

  • It's worth pointing out that the control board load traces can only handle 5.5A even though the relay is 30A (per calculations others made in the comments on the control board itself).
    The limitation should be included in giant red letters in the tutorial.

  • What's better than NOT getting free stuff? Spamming the refresh button for 3 hours to answer 8 questions! I found it quite exhilarating to see the page load when I did get through!

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