Help with Expanding the Range of an IR Transceiver and Receiver

Discussion in 'The Projects Forum' started by JoeBro391, Sep 12, 2010.

  1. JoeBro391

    Thread Starter Member

    May 15, 2010
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    Okay, so most of you have probably seen my exploits about using a mic to detect sound and either power a lone LED or connect to the inputs of a LM3915/16 bar-graph display IC. Well, i'm still taking things one step at a time, but since last year, my VU meter was attached to my laptop via cable, I was to try to branch out and send the signal wirelessly.

    This is my first wireless project and I'm actually pretty happy with the results, however, I can only get a range of about a foot to two feet. I've attached the schematics for the receiver and transceiver below.
    transceiver.jpg
    receiver.jpg

    I'd like to be able to attach the outputs of the receiver to a LM3915 IC. Right now I'm lighting up a simple LED successfully, but the range stinks. It definitely won't reach the 10 feet across my dorm. How do TV remotes combat this problem??

    So any comments and ideas. I really like the idea of using simple, discrete components, but I'm open to ideas. If you have any questions about parts or values, just ask. Thanks for any help you can provide. -Joe
     
  2. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    Firstly some questions.

    Are you sure it is an IR LED?

    Are you protecting the phototransistor from natural light? (should not be nessecary but could help if it doesn't have an IR filter)

    You could also try using 3 or 4 IR LEDs and driving them with a bigger transistor.

    Another option could be to use some small RF modules. They are reasonably cheap and easy to set up.
     
  3. JoeBro391

    Thread Starter Member

    May 15, 2010
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    Yea, it's a black IR detector, not a clear phototransistor. I tested the circuit with a phototransistor, but it obviously functioned improperly cause it didn't filter visible light.

    yea, I think I'll try that. What time of transistor should I use in this case??

    I have absolutely no experience with RF modules, but if you have a site or something that I can read up on the subject, feel free to point me in a direction.

    -Joe
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    The IR emitter diode in a typical TV remote is operated in the pulsed stage which allows them to crank out a lot more light intensity in brief pulses using the same amount of overall power.

    I think I used the 17* one of these two, but note that if you run them at around an 8% duty cycle you can pump some heavy current into them:
    http://www.vishay.com/docs/81010/tsal6200.pdf
    http://www.mouser.com/catalog/specsheets/tsal7600.pdf

    You can also increase the range of your receiver by placing a magnifying glass in front of it and experimenting for the best placement, I used to use those credit card sized fresnel "card lenses"
     
  5. JoeBro391

    Thread Starter Member

    May 15, 2010
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    marshallf3: Ah, that's true, since it's popping out at around 45kH, it can be fired at a much higher voltage! Too bad that's not an option here :/. Though I'll definitely look for some more high-power IR LED's in the future. -Joe
     
    Last edited: Sep 12, 2010
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
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    It's not the actual frequency but the duty cycle that makes the difference - the percentage of time it's on vs the percentage of time it's off. If it's only lit 10% of the time you can theoretically put 10x the amperage through it per pulse to achieve the same average power dissipation but that's rarely the rule, the spec sheets will usually give you a suggested maximum pulse current.

    A perfect square wave would illustrate a 50% duty cycle.
     
  7. JoeBro391

    Thread Starter Member

    May 15, 2010
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    marshallf3, yea, that's the basis behind PWM. But since I'm sending an audio-signal, that idea is out. Right now, i'm messing around with multiple IR Emitters, and i'm definitely getting better range, but it's really hard lining the receiver up with the emitter. -Joe

    PS: what about adding another receiver? Or would that just make it more susceptible to picking up stray IR light?? I have about a dozen of them laying around
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    If you have a small flash light around try using the parabolic reflector from it as way to focus your IR source.
     
  9. JoeBro391

    Thread Starter Member

    May 15, 2010
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    So far, I've added two more IR LED's to the transceiver and 2 more IR Detectors to the receiver (all in parallel). I'm definitely getting better distance, but only about 5 feet when I'd like to get about 10 feet (from one end of my dorm to the other).

    How did my old pair or wireless headphone be able to send it's signal about 20 feet, and through minor obstructions?? All I remember was that the transceiver had 4 IR LED's and the headphones had 2 IR Detectors (one for left and channel and one for right channel). I already too it apart for another wireless project, but this time I really want to just make my own.

    Any thoughts about boosting the Voltage for the transceiver?? It's currently at 6V with 3 IR LED's in parallel with a single 10-ohm transistor to limit current through them. Any thoughts about boosting the voltage to 9V and upping the resistance a little bit less than linearly?? It'd equal about the same current, but more voltage. Not quite sure how that'd turn out, but I don't want to burn out my only IR LED's. -Joe
     
  10. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Your wireless headphones worked on the modulated carrier method and probably sent digital signals that were encoded at the set and decoded at the headphones.

    I wouldn't go messing about with the LEDs until you look at the spec sheets, but since you're sending audio through them you've got some headroom as that isn't 100% on all the time.
     
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