can somebody please correct me (infrared LED)

Discussion in 'The Projects Forum' started by aespino88, Apr 22, 2010.

  1. aespino88

    Thread Starter Member

    Mar 31, 2010
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    i tried to make an infrared object sensor, the sensor light works (its stays on no matter what ever is in front) just not the object sensor part. could somebody please explain what i did wrong and how to correct it. thanks.

    i used a green square LED, a 100 ohm resistor, a transistor, infrared LED and receiver, and i powered it with 3 AAAs from a LED flashlight. all from radioshack cept the batteries.
     
  2. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Before we can help you, we need a schematic to examine your circuit.

    Austin
     
  3. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    i don't know how to draw schematics but i'll explain the best way i can.

    from the + power i connected the collector peg of the transistor, also from the + power i connected the infrared LED and in series the matching receiver LED (i covered them with some paper from the package so it wouldn't have problem with the light from the green LED) from there it went to the base peg of the transistor, from the + power i put the resistor to the base peg. then i put the green square LED from the emitter peg of the transistor to the - power.

    please refer to the pics
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Oh boy. If the IR receiver ever got turned on, it would have turned on the IR emitter, which would keep the IR receiver turned on. Since it doesn't sound like you have a resistor between the IR emitter, IR receiver and the base of the transistor, you may have fried all three of them.

    You really need to learn how to make a schematic. Trying to explain things in words just makes it far too easy to have a misunderstanding.

    You can download Linear Technology's LTSpice program for free.
    Google "LTSpice download".
     
  5. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    so do i just add a resistor between the receiver, emitter, and receiver n base peg????
    would all those resistors add up or would the whole circuit stay at 100 ohms???
    did i do right in having the infrared and receiver in series?
     
  6. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    The IR LED has to be connected between +V and -V with a resistor to keep the current to a safe limit. The rest of the circuit does not seem to work.
    The 100 ohm resistor from base to +V will keep the transistor turned on all the time regardless of what else is happening.
     
  7. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
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    so if i just move the resistor from the + power to the base to between the + power and IR LED it should work as a object sensor?
     
  8. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    ok i switched the resistor but still nothing. how do i get the infrared led to detect whether theres an object or not???
     
  9. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    this is the schematic for the object sensor i made. i didn't know the symbol for the infrared LED, but i think everything else is correct. i hope. somebody please help
     
  10. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Do you even know if your IR emitter is on? Get a digital camera and see if you can detect light coming from the IR emitter. Our eyes aren't capable of seeing IR light, but cameras can. That will tell you whether your IR emitter is on or not.

    Austin
     
  11. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    will the camera on my phone work? i can't find my kodak camera.
     
  12. electronicslover

    New Member

    Mar 5, 2010
    28
    1
    yes...using your camera in the phone..you will be able to see the IR led glowing if it has not been damaged... :)
     
  13. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    how can you tell if they haven't been damaged?
     
  14. Blackbull

    Well-Known Member

    Jul 26, 2008
    70
    6
    I haven’t seen a board with the tracks uppermost before, could be a bit tricky soldering DIP packages etc. in that fashion!
     
  15. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    If they haven't been damaged, your cellphone camera will see a light in the led.
     
  16. aespino88

    Thread Starter Member

    Mar 31, 2010
    41
    0
    they don't seem to be workin. could somebody draw simple schematic using the same components?
     
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