LED connect to Transistor And gate circuit bright all time.

Discussion in 'General Electronics Chat' started by mmc01, Jul 21, 2014.

  1. mmc01

    Thread Starter New Member

    Jul 27, 2010
    6
    0
    I connect LDR and PIR sensor to input of Transistor And gate circuit and connect 4 LED 12V 1W to output . But LED is bright all time. when have no input from both sensor LED is little bright. So, I pull out input from LDR. when somebody pass PIR sensor it's more bright . And If have input from both sensor it's most bright. I want only ON/OFF LED not want little bright. I want to set LED output hight (12V) when input from LDR and PIR sensor is hight only. I'm not sure can it use with opamp comparator. how to fix it.

    [​IMG]
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi mm,

    Is your circuit complete.?? R9 looks incorrectly connected?

    Also the value of R1.?
    E
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    Your LDR circuit has no positive voltage supply.
     
  4. shakilabanu

    Member

    Jul 8, 2014
    44
    2
    There are clearly multiple mistakes with this schematic, and purely accidental if this circuit is doing anything close to what you are aiming for... you need to relook the schematic.
     
  5. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    There is no power to the PIR sensor as drawn.

    Bob
     
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