proximity sensor problem

Discussion in 'The Projects Forum' started by aespino88, Apr 30, 2010.

  1. aespino88

    Thread Starter Member

    Mar 31, 2010
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    hey guys i made this proximity sensor but it doesn't seem to work like it should. the led stays on and only get brighter when it senses something. it also only reaches about an inch if that. i have to put my finger right in front almost touching the IR LED. i used 3 AAAs to power it. how could i get it to go from complete off until theres an object in front and how could i get it to reach 5 more inches???
     
  2. roltex_rohit123

    Member

    Jan 1, 2010
    72
    0
    what sensor do you use? are you using the PIR sensor? if so then get the Datasheet before using the part. I think most of the PIR sensors are powered from 3-15 volts.
    check this site
    http://www.futurlec.com/PIR_Sensors.shtml

    they offer cheap and good parts
     
  3. hgmjr

    Moderator

    Jan 28, 2005
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    214
    It would be helpful if you provide us with the details of what you are trying to do with this detector circuit. For example, what range are you expecting to detect whatever object you are trying to detect.

    I think you are trying to put together your own reflective IR sensor module. Often the performance of reflective sensors is intentionally limited to short distances. A quarter of an inch from the reflective sensor is about the maximum effective distance. To achieve greater distances requires that you pulse the IR transmitter with their maximum current for a very short period to avoid damaging the IR transmitter.

    hgmjr
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    And you should really put some kind of divider in between the detector and emitter, so you will not get any side illumination from the emitter. Having them that close to each other you are basically shinning the IR right into the side of the photo detector.


    You should also place the circuit in a housing with some kind of filter lens to block out ambient light from getting to the detector...

    B. Morse
     
  5. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    i got the IR LED from radioshack it came as a pair. i want to use the sensor as a light switch for about 4 or 5 LEDs. how could i get it to have a 4 to 5 inch range? was my schematic correct? i don't really know how to draw them but i'm really tryin to learn.
     
  6. hgmjr

    Moderator

    Jan 28, 2005
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    Is it your idea to use this circuit to turn this bank of 4 or 5 LEDs on by waving your hand in the path of the IR reflective sensor circuit you have built?

    hgmjr
     
  7. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    i want the the LEDs to come on when theres an object present, and to turn off when its removed.
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Is it reflective detection or pass through detection?
    For reflection you will need more sensitivity.

    Bertus
     
  9. aespino88

    Thread Starter Member

    Mar 31, 2010
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    i guess reflective. how could i make it more sensitive?
     
  10. bertus

    Administrator

    Apr 5, 2008
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  11. hgmjr

    Moderator

    Jan 28, 2005
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    The problem with attempting to extend the range of the reflective sensor is that you end up making the receiver so sensitive that it begins to respond to ambient light.

    The typical solution involves pulsing the IR led and then using an ac coupled receiver. Such a design is a good deal more complex.

    hgmjr
     
  12. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    is there a certain op amp i need to use?
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did you read the header of the page I gave you?

    To have less influence of the surrounding light you could place the IR led and the IR transistor into seperate tubes.

    Bertus
     
  14. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    where could i get this opamp?
     
  15. bertus

    Administrator

    Apr 5, 2008
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