Optical Sensor (Time to decode - TTD)

Discussion in 'The Projects Forum' started by bc627, May 20, 2013.

  1. bc627

    Thread Starter New Member

    May 20, 2013
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    i am working on a school project and need to design a circuit that will decode the time it takes once a light is triggered to the time it goes off (time to decode - TTD).. i have some ideas but i am somewhat of a newbie.. any help would be greatly appreciated.. -thank guys
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    We can help but you will have to explain a bit more clearly what you are attempting to do.

    What do you mean by "light is triggered to the time it goes off"?

    What level school work is this?
     
  3. bc627

    Thread Starter New Member

    May 20, 2013
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    this is for my engineering class (undergrad)
    we will be triggering a device that sets off a light that will remain on for a variable amount of time from 0-10sec (measuring only ms and sec)
    We would like to count the time it takes once it is triggerd to the time it cuts off ex: light on - light off = .143ms
    We are goin to implement a microcontroller and a light sensor and send the information via usb to our laptop
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    What turns off the light?
     
  5. bc627

    Thread Starter New Member

    May 20, 2013
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    its an external trigger which has already been configured
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Use a photosensor and measure the duration that the sensor receives light.
     
  7. bc627

    Thread Starter New Member

    May 20, 2013
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    ive had a few ideas, but not sure if theyd work.. 2 photo transistors.. maybe an LDR so the counter starts when light is on so the resistance drops using an opamp to bias transistor to relay
     
  8. bc627

    Thread Starter New Member

    May 20, 2013
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    any ideas on how to design the circuit so it functions properly?
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    What relay? I thought you just wanted to measure the time the light is on.
    Connect the output of the photosensor to an input pin of the microcontroller.
     
  10. bc627

    Thread Starter New Member

    May 20, 2013
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    more or less yea... i just want to trigger the light, initiate timer.. light goes off.. stop timer.. send data to computer.. it just seems like there would be more to it then just that.. u made is sound so simple
     
  11. wayneh

    Expert

    Sep 9, 2010
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    If you want complicated ... try here.
     
  12. LDC3

    Active Member

    Apr 27, 2013
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    I think the calculation delay might be toooooo long. :D
     
  13. LDC3

    Active Member

    Apr 27, 2013
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    The microcontroller is the timer, so you don't need a separate timer.
     
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