IR proximity sensor

Discussion in 'Embedded Systems and Microcontrollers' started by varuntejavarma, May 12, 2014.

  1. varuntejavarma

    Thread Starter Member

    Apr 16, 2014
    36
    1
    Hello,

    I am a beginner who started working with circuits and microcontrollers recently. I am doing a project on IR proximity sensor.

    I have started with a basic proximity sensor circuit available in internet. But i couldn't achieve long range with that sensor. So, I came to know that i can improve the range and efficiency of the Ir sensor if a modulate it to a particular frequency.

    My Hurdles:

    How to modulate the Ir led to 56Khz using a PIC18f4550 mcu (program and explanation)

    how should i connect a bandpass filter in the reciever circuit(with appropriate res and cap values so as to allow only 56khz signals), amplifier to amplify the signal. {explanation with circuit diagram would be of great help}

    Please dont mind to explain me in detail as i am new to this field. so, It takes some time for me to understand the working of the circuit or program.

    Any kind of help would be appreciated

    Regards,
    Varun
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,447
    3,363
    You can use a 555 timer astable circuit to drive the LED

    What range are you aiming for?

    38kHz is a typical modulating frequency. You can buy sensors that are ready to receive at 38kHz.
     
  3. varuntejavarma

    Thread Starter Member

    Apr 16, 2014
    36
    1
    @MR.chips I should use a microxontroller in my circuit anyway. so, thought of utilizing it even for creating pulses instead of using a timer..
    I dont know.. just my thought.. which one do you think is better??


    As there are so many Ir sources pulsed at 38khz around us. I dont want to trigger the circuit from other source. so, thought of using 56khz

    I am aiming for a range of 1.5 meter. Is it possible?

    A detailed explanation would be very much appreciated. you can also mail me at : iamtony1991@gmail.com
     
    Last edited: May 13, 2014
  4. varuntejavarma

    Thread Starter Member

    Apr 16, 2014
    36
    1
    I thought of using 56 khz so that i wont mess with other 38khz signals. Is it too hard to modulate the led to 56 khz or is it possible using pic 18f4550. I dont know how to do the calculations. I am confused with calculating the prescale value.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
    1,606
    It's possible to use the PIC for that. I'm less sure about rejecting 38kHz in a 56kHz amp (I don't work with things such as that to know).

    I would have to ask how are you determining if something is close? Are you measuring distance or just looking for a reflection of your signal?
     
  6. varuntejavarma

    Thread Starter Member

    Apr 16, 2014
    36
    1
    could you explain me how to modulate the signal at 56 khz and which oscillator is better to use in pic18f4550. I am confused by different information i get in internet.

    I am looking just for a reflection but in a long range upto 1.5 meters.

    Any kind of help would be appreciated
     
  7. varuntejavarma

    Thread Starter Member

    Apr 16, 2014
    36
    1
    Hello,

    I have tried to modulate the signal using 555 timer to test the 56 khz photodiode. It seems to be working. It shows 0v when there is a obstacle and 5v when there isnt any. But the range is not improved. It detects an obstacle only in the range of 2-3 inches.

    how can i increase the range of detection
    how can i increase the intensity of Ir led

    What values should i change in the circuit
    [​IMG]
     
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