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  • What is the use of optocoupler in this circuit?

    prasadaraju

    Member

    Updated: Oct 26, 2024
    Views: 1.3K
    [​IMG]


    R1-7-9=1Kohm
    R2-3-4-5=100Kohm
    R6 =10Kohm
    R9 =47Kohm
    IC1 = 4066
    IC2 =4N25
    Q1-2=BC550
    S1...11=Push button sw or keyboard
    S12=Push button normal closed
    All resistors is 1/4W 5%

    can i get an output of putting an led at 5th pin of optocoupler and by pressing 1,4,7 .
    will the led glows when 1,4,7 is pressed ,
    can u tell me any modifications if the circuit is wrong if u think
    please reply for all as i m in very hard situation
    0
    Replies
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Replies

  • Kaustubh Katdare

    Administrator • Aug 27, 2009

    Thread moved to electrical & electronics engineering section.
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  • reachrkata

    Member • Aug 29, 2009

    I can think of only 1 reason - GROUND ISOLATION.

    -Karthik
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  • prasadaraju

    Member • Aug 29, 2009

    ground isolation?
    i cant get u clearly?
    can u xplain clearly plzzzzzzzzz
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  • Kaustubh Katdare

    Administrator • Aug 29, 2009

    prasadaraju
    ground isolation?
    i cant get u clearly?
    can u xplain clearly plzzzzzzzzz
    SMS text is strictly NOT allowed on CrazyEngineers.
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  • skipper

    Member • Aug 29, 2009

    If it's a security lock, maybe the optical coupler is the switch that's opened when you go through?
    So the alarm goes if the code entered is wrong, then the switch is opened (the beam is broken)...?

    Given the simple design, off the top I would guess that the ICs are latches (set by the switches), the S12 is probably to reset the latch condition.
    If you don't press the buttons in the right order it doesn't latch and the optocoupler stays on so the beam is interrupted and the alarm goes?
    Or, the latch enabkes the opto, and you have to break the beam to reset the lock...?

    You really need more details, but I would say it's one or the other.
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  • prasadaraju

    Member • Aug 29, 2009

    vcan u tell me some more about it
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  • Muffy

    Member • Aug 31, 2009

    The only function of the opto-coupler in this circuit is to provide an opportunity to have a wide variety of output stages. For example you could connect a micro controller circuit at the output of the op coupler , or a simple relay , or a solenoid (door lock, since its obviously a security system).
    The presence of the opto-coupler dose not alter the operation of the circuit in anyway. But the circuit by itself has no meaning you will have to add a circuit at the output of the op coupler if you want to achieve something useful.

    Hope this helps :smile:

    Good Luck.
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  • mishra

    Member • Sep 1, 2009

    can u please tell me..that why we use only NPN transistor in an optocoupler....??
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  • reachrkata

    Member • Sep 2, 2009

    That is because the behavior of the component is such. Whenever a current flows through the LED in the Opto, we expect the switch (phototransistor) to close. This action is same as that of a npn transistor.

    - Karthik
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  • prasadaraju

    Member • Sep 2, 2009

    can u explain the detailed operation
    can u tell me wat is the value of R8,R9 RESISTORS
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  • shaswat

    Member • Sep 2, 2009

    optocoulpler is given to electrically isolate one part of the circuit to the other part. so that in case of any damage in one part will not affect the other part of the circuit.
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  • Muffy

    Member • Sep 2, 2009

    @prasadaraju: Can you tell us the IC number? It would be easier to figure out the operation. It seems like a quad bilateral switch, perhaps a 4066?
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  • prasadaraju

    Member • Sep 2, 2009

    ya it is 4066
    optocoupler ic is 4n25
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  • mishra

    Member • Sep 8, 2009

    Hey thanks karthik...it is commendable dat u replied my ques
    i'll surely come with more queris further
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  • unkunny

    Member • Sep 10, 2009

    Possibly to isolate Analog Gnd from Digital Gnd ....
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  • prasadaraju

    Member • Sep 10, 2009

    [​IMG]


    R1-7-9=1Kohm
    R2-3-4-5=100Kohm
    R6 =10Kohm
    R9 =47Kohm
    IC1 = 4066
    IC2 =4N25
    Q1-2=BC550
    S1...11=Push button sw or keyboard
    S12=Push button normal closed
    All resistors is 1/4W 5%

    can i get an output of putting an led at 5th pin of optocoupler and by pressing 1,4,7 .
    will the led glows when 1,4,7 is pressed ,
    can u tell me any modifications if the circuit is wrong if u think
    please reply for all as i m in very hard situation
    Are you sure? This action cannot be undone.
    Cancel

  • Muffy

    Member • Sep 12, 2009

    You could use an LED at the output of the optocoupler, but the more sensible option would be to neglect the optocoupler and use an LED in its place. Pressing 1,4, 7 in sequence would illuminate the LED.
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  • prasadaraju

    Member • Sep 12, 2009

    the circuit is working by just pressing 7
    but can u suggest any modifications if any to get ouput by only perssing 1,4,7
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  • Ashraf HZ

    Member • Sep 13, 2009

    shaswat
    optocoulpler is given to electrically isolate one part of the circuit to the other part. so that in case of any damage in one part will not affect the other part of the circuit.
    Yes, this is probably true in this case. A secondary circuit, such as for the operation of an solenoid lock would require much higher voltages and current.. which would probably fry the ICs used in the primary circuit 😀
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  • prasadaraju

    Member • Sep 18, 2009

    as i m going to connect this i am getting some malfunctions in circuit ?can u help me

    by pressing only 7 also i am geetting output at 1st pin of optocoupler
    can you tell me why is it happening so?
    can u sugggest any other modifications if any?
    also can u clearly explain how each component working?
    please help me sir.





    [​IMG]


    R1-7-9=1Kohm
    R2-3-4-5=100Kohm
    R6 =10Kohm
    R9 =47Kohm
    IC1 = 4066
    IC2 =4N25
    Q1-2=BC550
    S1...11=Push button sw or keyboard
    S12=Push button normal closed
    All resistors is 1/4W 5%

    can i get an output of putting an led at 5th pin of optocoupler and by pressing 1,4,7 .
    will the led glows when 1,4,7 is pressed ,
    can u tell me any modifications if the circuit is wrong if u think
    please reply for all as i m in very hard situation
    Are you sure? This action cannot be undone.
    Cancel

  • reachrkata

    Member • Sep 18, 2009

    Yes you will see an output at pin 1 of the Opto. But this will not be useful because the R1 = 100kOhm and this high resistance will prevent the Photo-diode inside the opto from working because the current is very low.

    Only after pressing 1,4,7 will the photo-diode work properly because now the current would be supplied through R7 which is only 1kOhm.

    To check the output here is what you can do -
    1) Connect Pin 5 of the Opto to (say) 10V through a 1K resistor and also a normal LED.
    2) Connect pin 4 of the opto to Ground.

    You should see that when you press 1,4 & 7, the LED would glow.

    - Karthik
    😁
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  • prasadaraju

    Member • Sep 19, 2009

    that means

    that means i have to connect a 1kohm resistor and led between 5th pin of opto and 9v .....is this what you are saying
    can u reply me
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  • reachrkata

    Member • Sep 21, 2009

    Exactly ! Plus also connect pin 4 to GND.

    -Karthik
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