Analog Breathalyser

Discussion in 'Homework Help' started by Top-Dog, Mar 1, 2013.

  1. Top-Dog

    Thread Starter Member

    Mar 1, 2013
    36
    0
    Hi, I need to create a completely analog circuit that uses the MQ-3 alcohol gas sensor to determine the BAC of the user (I can use timers like the 555 too). The circuit has to operate between 7 - 9v and should minimise noise and be operationally stable. The output should provide at least a 3 step 'resolution' e.g. sober, tipsy, drunk.

    I would like to increase the output resolution and use a led bar graph with 10 steps. The MQ-3 requires +5v DC (or AC), so I think that it would make sense to use a 5v regulator to power the sensor, op-amps, LEDs... I would also like to implement some function that would be able to let the user calibrate the sensor, and provide a warm-up timer (since it takes ~20 sec for the heater to warm up).

    If you could provide some ideas about how to implement these functions and filter the signal that would be appreciated (i.e what 'stages' are needed to get a useful output from the sensor).

    Thanks
     
  2. #12

    Expert

    Nov 30, 2010
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    Is this a school assignment? We have a section just for those.
     
  3. Top-Dog

    Thread Starter Member

    Mar 1, 2013
    36
    0
    Yep, should it be under the "Homework Help" section?
     
  4. #12

    Expert

    Nov 30, 2010
    16,248
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    I'll tell the boss.
     
  5. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
  6. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    Not the boss, more like one of the head grunts.
     
  7. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    It just sounds so much better to call you the boss instead of a "grunt":D
     
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