IR Audio Receiver

Discussion in 'The Projects Forum' started by kpraytor, Oct 8, 2009.

  1. kpraytor

    Thread Starter New Member

    Oct 8, 2009
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    Hello everyone!

    I am trying to make a simple go/ no go tester to determine if a remote control is outputting an IR signal. There is no need to clean up the signal or do anything else with it; I just need to know if the remote control is putting out any kind of IR.

    I have attached the first design I had. This appeared to function correctly but the signal was not strong enough to make a very audible note, aka you had to hold the speaker up to your ear to here the noise being produced.

    Unfortunately, I crossed some wires while testing it and fried the only speaker I had. Now, I am forced to go with a Piezo transducer to output an audio signal. It says on the packaging that it requires a driver circuit (?). I am new to the whole electronics thing and would like some advice concerning how to approach this driver circuit.

    Thanks for all your help and I look forward to the responses!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Stick a visible LED in there and watch it flash.
     
  3. ELECTRONERD

    Senior Member

    May 26, 2009
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    kpraytor,

    Do you have a oscilloscope? You can stick a IR detector on the scope and then pass the IR emitter over it, you should see the oscilloscope waveform move around a bit. If you can't do this, a simpler method can be done using a digital camera. Based upon the fact that the human eye can't see any IR light, camera's can though. Using that fact, if you just pass the digital camera over the IR emitter, you should see a blue light coming from the source. That way, you'll know if you have IR light.
     
  4. kpraytor

    Thread Starter New Member

    Oct 8, 2009
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    Thank you for the good ideas, but I am needing this on some sort of permanent basis. I won't always have a camera with me that can see the IR "light", and i really would like something audible as opposed to visible.

    Thanks again for all the responses.
     
  5. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Oh I see, well my previous suggestions were just so that you could make sure you were getting IR from the remote.
     
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Try using a Piezo Buzzer instead of a speaker.... a lot more audible than a plain speaker with no amplifier.....

    try this circuit......
     
  7. kpraytor

    Thread Starter New Member

    Oct 8, 2009
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    Wow! That is incredibly simple. Let me give this buzzer a shot, and I will get back to you in an hour or so.
     
  8. kpraytor

    Thread Starter New Member

    Oct 8, 2009
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    BMorse, I just wired this up and it works like a charm. Apparently, I was trying to complicate things much more than they needed to be.

    I owe you a case of beer/new purse (depending on gender)! LOL

    Thanks again for this simplistic design.
     
  9. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    That would be beer.... and you are welcome, that is why I am here, to help and be helped...
     
  10. hgmjr

    Moderator

    Jan 28, 2005
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    If you have a cellphone with a camera in it, just like electronerd has described you can use it to view the IR LEDs output using the cellphone. Most people carry a cellphone around with them regularly.

    hgmjr
     
  11. kpraytor

    Thread Starter New Member

    Oct 8, 2009
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    Ok, the first circuit I wired up, according to BMorse's schematic, works like a charm. Unfortunately, I had to go purchase some more piezo buzzers. These are your basic buzzers from RadioShack, Part #273-074.

    After I had constructed the 2nd & 3rd "chirpers", there is now a high pitch whine that is continuously emitted from the buzzer. The functionality of the circuit is still there; you do get a different and distinct set of tones when IR is applied to the phototransistor.

    Unfortunately, I do not know what is the problem with these new buzzers. I wired up two seperate circuits, and they both emit this same high- pitch whine. I checked all of the leads and connections, and none of them are shorted; I checked them with a microscope.

    Again, any and all help and feedback is thoroughly appreciated. Thanks again!
     
  12. hgmjr

    Moderator

    Jan 28, 2005
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    It sounds like your NPN transistor is not turning off completely when there is no IR light falling on your detector. You could try putting 47K resistor from base to emitter to insure that the transistor is turned off when there is no IR light present.

    hgmjr
     
  13. kpraytor

    Thread Starter New Member

    Oct 8, 2009
    11
    0
    Thank you so much for the idea. I will give this a shot and return with results.
     
  14. kpraytor

    Thread Starter New Member

    Oct 8, 2009
    11
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    Ok, I have attempted this 47K resistor from the base to the emitter, but I think I am attaching it wrong. Take a look at the attached schematic and let me know what you think.

    Thanks again!
     
  15. hgmjr

    Moderator

    Jan 28, 2005
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    That is what I had in mind. If you are still getting residual buzzer output then I would suggest you lower the value of the 47K resistor to 22K or even 10K would probably be reasonable.

    hgmjr
     
  16. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    It sounds like you are getting ambient light noise, the humming is most likely from the fluorescent lights you have above you (You do have fluorescent lights, right? You can test for this by taking the circuit in a dark room and see if the humming stops.) anyways, here is a revised circuit so you can have some sensitivity adjustment.....

    Plus - you will have to put the IR Phototransistor circuit in some kind of case / enclosure to block out ambient light, You can try shrink tubing to put around the PhotoTransistor, leave just a small opening at the tip, this will narrow its angle a bit but it could help. Or put it in a small enclosure that fits the battery and everything, cut a 3/16" - to a 1/4" hole in the enclosure so you could "aim" it out the hole, but place it about a 1/4" away from the hole, and find some developed film negative, on the end of one of those negatives will be some developed parts without any images on it, cut some big enough to overlap the hole, use up to 2 to 3 layers, try 1 layer at a time to see if this is enough.


    Hope this helps..... the first circuit really didn't take in consideration the 9 volt supply and the pulldown for the 3904 to make sure it shuts off properly.

    And the circuit will produce different tones when different levels of IR intensity hits it....
     
    Last edited: Oct 9, 2009
  17. hgmjr

    Moderator

    Jan 28, 2005
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    Bmorse,

    Isn't the 10K ohm (R1) in series with the 9V power going to prevent the circuit from getting enough current to operate?

    hgmjr
     
  18. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Yeah, on second thought, I built it on a breadboard and 10K would limit the current, just remove that resistor from the circuit and it should work just fine with the 9 volt battery (When I first tried it, I had it connected to my regulated 12 volt psu, and it worked then....)

    I also played around with different IR photo transistors and such, and the ones in a clear casing definitely will be affected by ambient lighting, I had tried a clear one and I got the squealing noise... I found the dark colored ones (with daylight filters) work much better....
     
    Last edited: Oct 9, 2009
  19. bigcape

    Member

    Sep 18, 2009
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    0
    Digital cameras are supposed to have UV and IR filters to remove the IR for areason. Why does it work then. My cell phone camera does not have one?
     
  20. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    Most digital cameras and phone cameras are CMOS sensors, and they can pick up IR and UV light, most of these will have a filter on the lens(red color on camera lens), except it does not block out all IR. If the IR lens is replaced with developed film negative, it will block out most other wavelengths except for IR.... here is an example pic I took with a cmos imaging camera with the filter removed....
     
    Last edited: Oct 10, 2009
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