ir receiver not working?

Discussion in 'The Projects Forum' started by chimera, Oct 27, 2010.

  1. chimera

    Thread Starter Member

    Oct 21, 2010
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    to summarize: designed a 555 timer astable circuit to pulse an IR led at 38Khz. Then placed a 38Khz IR reciever RIGHT infront of it. I cant get a steady reading out of the reciever. Im supplying it with 5V and its outputing like 3V. The reciever is placed directly opposite to the IR led. has the reciever gone bad? Caz, ideally, if it should detect an IR input, it should output some voltage (dont know at which level) and if it doesnt it should output zero. I tred dimming out the lights and placing a aluminum foil in between the led and the reciever and then measure so that i could account for ambient lighting. Still the same confusion. Whats going on? Please help!!!
     
  2. R!f@@

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    Apr 2, 2009
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    Show ur receiver config
     
  3. chimera

    Thread Starter Member

    Oct 21, 2010
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    i didnt know exactly what u meant but i drew the reciever and attached it. I have placed the reciever at the actual distance as it is in the real circuit. btw..the parts are from radioshack...and thanks for taking a look at it. I really do appreciate your effort
     
  4. R!f@@

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    Did u power the receiver properly.
    What is the signal that get from the RX output.
    It shud be same as the modulated in put to the IR diode.
     
  5. chimera

    Thread Starter Member

    Oct 21, 2010
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    okay..i might have misunderstood. the output of the Rx should be the same as the output coming out of the pin 3 from the 555 timer? are u sure of that? caz thts the voltage the diode is working on (plus a resistor ofcourse). I just checked the circuit and the voltage out of the 555 is 2.15 while the volatge out of the Rx is 2.48. To verify that my circuit might be not be working as expected, I disconnected the IR diode to see if the Rx stopped to give any value at the output. As it turns out, the value of 2.48 was constant (with or without the IR diode). Ive attached a picture of the actual circuit. The Rx is powered by the same power supply as the 555 timer (5.3 volts--the package said that it can work from 2.4 till 5.5 volts) Thanks for your time r!f@@...your a really helpful person and ive honestly been really confused with this circuit :confused:
     
    Last edited: Oct 27, 2010
  6. R!f@@

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    Apr 2, 2009
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    First of all. reduce the voltage 5V and stay at it

    Looking at ur practical layout. I don't think it will work. U need a UV filter kinda thingy that blocks ambient light

    By the way, do u have access to a scope
     
    Last edited: Oct 27, 2010
  7. eblc1388

    Senior Member

    Nov 28, 2008
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    We are too, looking at the values of the components.

    With what you have provided so far, the output is no way near 38KHz, not even 3.8Hz.:eek:

    The breadboard picture you have provided is so dim that we can't figure out what value of the ceramic capacitor is being used instead.

    [​IMG]
     
  8. jpanhalt

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    Jan 18, 2008
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    I am afraid UV and so forth suggested by Rifaa is not the problem.

    It would be nice to know the part number for the IR receiver you are using. In the absence of that information, I will assume it is a conventional IR receiver that has two basic requirements:
    1) The IR is modulated at 38 KHz or whatever the specification for the receiver is. Call that the carrier.
    2) The carrier IR is ON/OFF modulated at a certain frequency.

    In the absence of the latter (#2) sensitivity is turned way down. There are various ways to do the second modulation. One simple way is to use two 555's or a single 556. Another way is to use a microcontroller.

    Finally, in answer to your question about whether the output of the IR receiver will mimic the output on pin 3 of the 555, the answer is "no." Most IR receivers simply give an on/off output showing whether the properly modulated IR is received or not.

    If you give us the part number for your IR receiver, we can give much more specific help.

    John
     
  9. jpanhalt

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    Jan 18, 2008
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    @Chimera,

    You have two threads asking the same question. That will be counterproductive and lead to confusion. Which thread do you want continued? Please tell a moderator.

    John
     
  10. R!f@@

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    Apr 2, 2009
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    I saw the OP's other thread too. I just tried to get the OP going, since most of u were offline.
    Not bad huh!!. I tried to keep the OP's hope up. I know one of u will simulate the diagram.
    I don't use spice.

    @john
    But One q though. The Rx shud see the Tx carrier in order to get it. I mean if no info is modulated then it's just the carrier alone. So why doesn't the Rx output the Tx carrier
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I closed the other thread with a link to this one.
    If you open more threads on the same subject it will only give confusion.

    Bertus
     
  12. jpanhalt

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    The datasheets for any of the IR modular receivers will explain that. Here is a link to a Vishay TSOP series: http://www.vishay.com/docs/81762/tsop391.pdf

    It is quite uncommon for any receiver, be it for light or RF, to output the carrier.

    John
     
  13. R!f@@

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    Man , I am old school in this.

    I had photo diode kind of thingy in my head when I answered.
    Never for once thought the new ones have built in light immunity and demodulation.
    Sorry..My bad.

    Thanks though for the info
     
  14. chimera

    Thread Starter Member

    Oct 21, 2010
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    well..firstly..i cant find what model number the Rx is..its from radioshack and all I need to do is stay with the limit for Vcc. Secondly, the 555 timer circuit is producing 37.8Khz because i ran a simulation using a computer. I plugged in the actual values i had recorded fr the components. But all of this goes to show that my circuit works but it doesnt tell as to why the Rx is not respondoming. Any suggestions?

    Oh and btw..i physically tied two 0.47nF together so they act as if their in parallel and the combined capacitance i get is 0.952nF..resulting in 37.8Khz frquency applied to the IR led.
     
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  15. jpanhalt

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    Jan 18, 2008
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    Can you post a picture the the RadioShack device. Is it the large (ca. 2 cm sq) canned device?


    See post #8. Did you not understand my comment about modulating the 38 KHz carrier?

    John
     
  16. Markd77

    Senior Member

    Sep 7, 2009
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    Have you tried using the camera on your mobile phone to look at the IR diode? You should be able to see something.
    Also from the 555 datasheet:
    I can't see those in your circuit.
     
  17. Papabravo

    Expert

    Feb 24, 2006
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    Does the IR receiver have an OPEN-COLLECTOR output requiring an external pullup resistor? If so, without that pullup resistor you will never see any output no matter what else you do.
     
    Last edited: Oct 27, 2010
  18. chimera

    Thread Starter Member

    Oct 21, 2010
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    okay i dont know if it needs a pull up resistor but i still tried it and it gave me a zero voltage reading. Although the circuit might not be working, there was atleast an output present. Now that could also mean that the pull up resistor is necessary and the Rx circuit now works. But since it cant detect the modulated IR beam, its not registring anything..

    Im supplying it with 5V and its outputing like 3V. The reciever is placed directly opposite to the IR led. has the reciever gone bad? Caz, ideally, if it should detect an IR input, it should output some voltage (dont know at which level) and if it doesnt it should output zero. I even remove the IR led and the Rx still inputs something..whereas it should go to zero.

    The part number from radioshack is:
    http://www.radioshack.com/product/index.jsp?productId=2049727

    Ive attached a picture in case. When ur looking at the picture, the left most pin is out (1), the center is gnd (2) and the third most right pic is Vcc(3). I cant find the data sheet for this particular model or make.

    I know this is frustrating guys but I appreciate all of ur efforts trying to help me debug when none of you have anything ivested in it. you all are really helpful and I can only thankyou guys for the time.:)
     
    Last edited: Oct 27, 2010
  19. chimera

    Thread Starter Member

    Oct 21, 2010
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    I think I might have figured out one of the reasons why Its not working. Take a look at page 3 of this data sheet. Pay attention to the Singal Gap time

    http://www.rev-ed.co.uk/docs/TSOP18.pdf

    Does this seem like a logical reason?
     
  20. jpanhalt

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    Jan 18, 2008
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    Yea, between posts I checked the RadioShack site and figured that might be the device. I did a quick check of Vishay. All of the 20 or so of its products I checked had a different pin-out and incorporated a pull-up resistor.

    IR is deceptive in terms of what it will penetrate. In my experience, good, black, vinyl electrical tape (e.g., 3M) will block it. With your pull-up resistor, see if covering the window with electrical tape changes the output you are seeing. BTW, Vishay (at least the ones I checked) are "active low." That is, the output of the receiver goes low ("zero") with the right IR signal.

    Any chance you can get another part (not RadioShack) for which you can get a real datasheet?

    John
     
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