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IR Jammer circuit not working

Discussion in 'General Electronics Discussion' started by sneitzke, Sep 3, 2011.

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  1. sneitzke

    sneitzke

    3
    0
    Sep 3, 2011
    Hello I'm new to electronic circuits and have been trying everything to get this circuit to work. Any help would be greatly appreciated.

    In this circuit I'm using:
    (These are all in right place on schematic)

    - 10k potentiometer
    - A 470 ohm resistor
    - A 1k ohm resistor
    - A 560 ohm resistor
    - A 47 ohm resistor in place of the 180 ohm
    - 2 High Output IR Led
    - A 555CN Timer
    - 2 10nf capacitors
    - A 2N3906 in place of BC557 (this may be wrong please comment if it is)
    - 2 1N4148 diodes

    I have attached the schematic which I used for this project.

    That is what I have in this circuit if there are any problems or concerns with this please tell me Thank you

    [​IMG]
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The major problem is that the current through the LEDs is going to be limited to about 3mA

    Once the voltage across the 180 ohm resistor exceeds about 0.7V, the 2 1N4148's shunt any additional current away from the base of the transistor.

    Are you sure the resistor isn't meant to be 18 ohms?

    Even with 18 ohms, the light output isn't going to be significant enough to jam IR transmitters unless this device is placed right next to the receiver. And if you're going to do that, a piece of black card would be more effective.
     
  3. sneitzke

    sneitzke

    3
    0
    Sep 3, 2011
    Thank you for the quick response! So should i just get rid of the resistor altogether? and also im currently using a 47 ohm will that, did not make the schematic and im not sure what that is supposed to be.
     
    Last edited: Sep 3, 2011
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    If you remove the resistor entirely, either the transistor or the LEDs (or possibly all three) will join the great electronics project in the sky.

    The LED current will be limited to approx 0.7/R Amps (or 700/R mA).

    If these LEDs are rated for 20mA then you would be safe setting the resistor for 30mA.

    Note also that you have an unlabelled pin on your 555. It should be labelled as pin 7 :)

    47 ohms gives you about 15mA.

    To get any significant range you would need to have a very short duty cycle and have the LED current much higher (but averaging 20mA or less). The datasheet on the LEDs would tell you what current you can use for a given duty cycle.
     
  5. sneitzke

    sneitzke

    3
    0
    Sep 3, 2011
    Thank you I have looked at the data sheets for my components and have found out that my LED's can take 100mA and my transistor can also take up to 200mA so with these ratings what resistor should i use? also thanks for the unlabeled pin :)
     
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