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two different inputs to photo diode reciever circuit, possible?

Discussion in 'Homework Help' started by Mindmywork, Oct 29, 2016.

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  1. Mindmywork

    Mindmywork Member

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    i want two different trigger (one time) outputs from a photo diode reciever circuit (at pin no 1), is it possible

    im using it for the street light project
    idea is to when a normal vehicle comes between ir and photo diode (trigger 1) then street light will lit up with their maximum efficiency.
    if a specific vehicle comes (like police, ambulance cars) between ir and photo diode (trigger 2) then street lights and flashing lights too will lit up
     

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  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    You would need a high power pulsed IR emitter to have a TX to RX path as wide as a street.
    One problem would be it would also detect pedestrians etc travelling along the street, thru the TX to RX beam.

    How do plan to detect a police/ambulance passing thru the TX to RX beam.

    We need more information.

    E

    BTW: Note your posted circuit is a DC operated system which means it will be effected by the ambient light conditions.
     
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  3. Mindmywork

    Mindmywork Member

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    I created two different circuits One for street lights,another for flash lights.
    All I can't able figure out how to trigger these two circuits with the same photo diode receiver circuit which is connected to the above two circuits.
    I have created a ir led and photo diode blockage input receiver for street lights.
    All I want is to produce another signal or trigger with the same photo diode receiver to trigger the flash lights also.
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi M,
    The IR detector will not detect the 'Blue' flashing light mounted on a Police car etc..

    E
     
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  6. spec

    spec Well-Known Member Most Helpful Member

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    Assuming that your detection side works OK, the answer to your question of post #1 is simply connect the output from the LM358 to the two trigger circuit inputs in parallel. It is as simple as that.:)

    It is good practice to isolate the output of an operational amplifier (opamp) from the capacitance and inductance of any load, so it would be wise to put one 47 Ohm resistor in series with each trigger circuit input. The resistors should be physically close to the opamp output pin.

    As you have not told us what the trigger circuits are, the above statements are based on the assumption that the trigger circuits have an input impedance of 1K Ohms or higher.

    Another point is that, as the LM358 opamp is configured as a comparator, it is wise to include some hysteresis so that the comparator changes from one state to another smartly. You can add hysteresis by adding a resistor from the LM358 output to the non-inverting input. The opamp would need a 100nF ceramic capacitor connected physically between its supply pins to help frequency stability and performance.

    And one final thing, an LM393 comparator makes a much better... er comparator than an LM358 opamp.:D

    spec
     
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  7. Mindmywork

    Mindmywork Member

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    Thanks spec for Ur suggestion.

    What I need is another trigger pulse from lm 358 when a special car enters. I can't figure it out.
    Is there any way I can get a two different output pulses from lm 358.
    One pulse to trigger only street lights (white LEDs in my project on the pole)another pulse to trigger street and flash lights(white and red blue flashing on the pole)
    I have a idea about adding a ir led to the special car at the opposite direction to the photo diode. But it will give the same output of ir and photodiode blockage circuit? Isn't it?
     
  8. spec

    spec Well-Known Member Most Helpful Member

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    No probs MMW,

    So what you need are two separate detectors to:
    (1) Detect all vehicles and produce an output to turn the street light on
    (2) Detect the police automobile flashing lights and turn a flashing light on and also turn the street lights on.

    Do you agree that this is your requirement?

    If so, the hard bit will be the design and development of the two detectors. The rest of the circuitry would be relatively straight forward (famous last words).:)

    spec
     
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  9. Mindmywork

    Mindmywork Member

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    Thanks for Ur response spec.
    Yup that is the requirement.
    I built a circuit which will produce a output when ir beam is blocked.
    I want the receiver same for the two pulses but the output must be two different pulses which can trigger connected circuits.

    I don't want to be using a flashing light of car as input just some another ir led which I will put to car(special ones like ambulances, police,fire engines).

    My question is that can I produce two outputs from same ir receiver circuit with change in ir transmitter(I.e ir led in my circuit)
     
  10. Mindmywork

    Mindmywork Member

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    My mother tongue is not English. So please excuse my English a bit.
     
  11. spec

    spec Well-Known Member Most Helpful Member

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    Your English is fine.:)

    Are you saying that the police vehicle can have a special transmitter that you can detect to turn the flashing street lights on?

    spec
     
  12. Mindmywork

    Mindmywork Member

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    Yeah. My question is that can we make photo diode receiver able to grasp the change. ???
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Our emergency vehicles have very bright white and red flashing lights that are detected and change traffic lights to allow the emergency vehicles through intersections, day and night. Our street lights are all LEDs now so they use low power and are always on at night.
     
  14. Mindmywork

    Mindmywork Member

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    I'm from India. This for school project and im the guide.
     
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