Testing of LM 311.

Discussion in 'The Projects Forum' started by saranya ajesh, Sep 26, 2011.

  1. saranya ajesh

    Thread Starter New Member

    Sep 26, 2011
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    0
    hi,
    I have an LM 311 IC with me. I need to check whether it is working or not.
    I don't have any testing equipment with me. Please guide me regarding the same.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here is a simple test circuit:

    [​IMG]

    When VR1 is about mid-position, a small movement one way or the other should turn the LED on and off.

    This is just a very quick and informal test. If you want to know if it is functioning according to manufacturer's specifications, you will need test equipment.
     
    saranya ajesh likes this.
  3. saranya ajesh

    Thread Starter New Member

    Sep 26, 2011
    4
    0
    Sir,
    Thank you for your reply. I implemented this circuit and got output. But I have doubts about its output section. Why we are connecting the cathode of LED to the output. Is it in reverse biased condition? [/COLOR]
     
  4. saranya ajesh

    Thread Starter New Member

    Sep 26, 2011
    4
    0
    Sir,
    Thank you so much for your reply, it helped me a lot. But sir I have one doubt about its output section. Why we are connecting the out put to the cathode terminal of the LED
    .

     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Pin 5 is the output of the comparator. It is an open-collector output. It can sink current from pin 5 to pin 6, but it cannot source current from pin 5.

    An LED will only light up if current flows through it in one direction. The anode must be more positive than the cathode in order for it to light.

    As shown, when the output is turned ON while adjusting VR1, current is sunk from the 9v supply V1 via the resistor R5 through the LED D1 to pin 5; this causes the LED to illuminate.
     
    Last edited: Oct 4, 2011
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