MOC7811 output swing limits?

Discussion in 'The Projects Forum' started by onlyvinod56, Aug 26, 2011.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    Hello,

    I have connected MOC7811 as per this circuit

    When there is an obstacle, the output voltage is 4.2V.
    When there is no obstacle, the output voltage is 4V.

    Is it not possible to get the output from 0V to 5V????
     
  2. ian123

    Member

    Aug 24, 2011
    73
    2
    Are you working under a light source . I had that problem years back found light from my desk was causing the base to turn on
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Are you certain that your voltages and resistance values are as shown in the schematic?

    Measure your supply voltage with your components connected. If the supply voltage is not 5v, then you need to say what it is.

    The 360 Ohm resistor may need to be adjusted if your voltage is different than 5v.
    If your output load is heavy, you may need to amplify the output signal. You don't say what it is.
     
  4. ian123

    Member

    Aug 24, 2011
    73
    2
    also make sure the obstacle is black some plastics allow infra red through
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    The current through the IR led is to low.
    In the datasheet 20 - 30 mA is given, you have about 12 mA.

    See the attached datasheet

    Bertus
     
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