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Thread: IR Communication by using PT2248/PT2249A

  1. #1
    DIY Junior Member munhann's Avatar
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    Exclamation IR Communication by using PT2248/PT2249A

    HI All,
    Recently i build a IR communication circuit and still fails to figure out what went wrong..
    I hope can get your expert help on this. Below are component list and attach files is my circuit schematics. Please help and this is urgent!!

    TX IR Component List
    - C1 = C2 = C3 = 120pF, C4 = 10nF (Polarized Capacitor)
    - XTAL = 455Khz
    - D1 = IN4002 and D2 = IN4148
    - Q1 = Q2 = PNP A1015
    - LED0 = Infrared Transmitting LED

    RX IR Component List
    - C1 = 100pf
    - R1 = R2 = 39K
    - 1738 IR Receiver (38Khz)
    - PNP A1015
    - Receiver IR Sensor
    Attached Images Attached Images   

  2. #2
    Jack of all trades DonL's Avatar
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    Welcome to Terry's Forums munhann,

    You can verify the IR transmitter is working, using a cell phones camera, You should be able to detect and see the IR.

    The output going to the 2313 has to be at least 2 wires, Your drawing only shows 1.
    You would need a ground return path for that output feeding the 2313 microcontroller.
    Or is it on a common power supply ?


    Enjoy your project.


    DonL
    Last edited by DonL; 07-06-2011 at 05:22 AM.
    Theory only works perfect in a vacuum.

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    Plumber jimbo's Avatar
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    I think you used putty instead of silcon on the XTAL, and the drain for Q2 needs to be 2" The whole thing is not vented.

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    DIY Senior Member BobL43's Avatar
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    Default Leaky circuit

    Quote Originally Posted by jimbo View Post
    I think you used putty instead of silcon on the XTAL, and the drain for Q2 needs to be 2" The whole thing is not vented.
    Jimbo, now you sound like a plumber talking And those 2 little arrows pointing out of the Light Emitting diode is the vent.
    Last edited by BobL43; 07-06-2011 at 06:56 AM.
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    DIY Senior Member BobL43's Avatar
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    Munhann,

    I see the tuned circuit on the remote sender oscillator is crystal controlled; is the r/c tuned to the same frequency?

    38KHz you specified as the receiver and the transmitter's crystal is 455KHz, the (almost) 12th harmonic of the receiver. I forgot most of this stuff 40 years ago, but maybe what I said will ring a bell for you. Was this a kit you built?

    And what Don said too
    Good Luck

    Bob
    I am definitely not a pro plumber, but I am a pro crastinator

  6. #6
    Jack of all trades DonL's Avatar
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    It looks like all the parts used are correct.

    The receiver has a built in Frequency Divider, and the 38khz is fine for the IR Band.
    The 455Khz is used because you can get them easy, Most are ceramic resonators and not really crystals.

    jimbo is correct tho "The whole thing is not vented."
    There is no place for the smoke to be released properly.

    If it passed the smoke test, then I would recommend getting the O-Scope out.
    It is hard seeing them electrons without the proper equipment.


    DonL
    Theory only works perfect in a vacuum.

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  7. #7
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by DonL View Post
    It looks like all the parts used are correct.

    The receiver has a built in Frequency Divider, and the 38khz is fine for the IR Band.
    The 455Khz is used because you can get them easy, Most are ceramic resonators and not really crystals.

    jimbo is correct tho "The whole thing is not vented."
    There is no place for the smoke to be released properly.

    If it passed the smoke test, then I would recommend getting the O-Scope out.
    It is hard seeing them electrons without the proper equipment.


    DonL
    I googled the chips, and this post looks like a cut and paste form the datasheets.

    as long as the thing is not in an enclosure, the factory smoke should be able to be released without a draft inducer fan. Just keep your face away from the board when it gets energized.

    by the way: URGENT?
    I am definitely not a pro plumber, but I am a pro crastinator

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    Jack of all trades DonL's Avatar
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    Do you have a link to that info Bob ?

    It sure looks like a waste, if that is the only part of the chips being used.

    I think I would have gone with a optic isolator. that would eliminate a lot of outside interference.

    What are you building Munhann ?

    What is your 2313 microcontroller doing with the data that it receives ?

    Hello Come in, Can you hear me now ? ...---... ...---... ...---...


    DonL
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  9. #9
    DIY Senior Member BobL43's Avatar
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    why soytanly Don, : http://www.datasheetcatalog.org/data...on/mXsswsw.pdf

    that's one, the transmiiter, the receiver is : huh! not getting too much on that, but this http://www.alldatasheet.com/datashee...C/PT2249A.html
    when I looked before, i saw the transmitter data sheet and thought that site had everything. Maybe it does, but too much drilling down for me right now
    oh!
    http://pdf1.alldatasheet.com/datashe...C/PT2249A.html
    Last edited by BobL43; 07-06-2011 at 08:16 AM.
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  10. #10
    Jack of all trades DonL's Avatar
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    Thanks Bob,


    Maybe Munhann will come fill us in on his project.

    It looks like a secret project. Over kill from what I can see, using that chip setup for 1 function.

    There must be a method for the madness. I am not knowing...


    DonL
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  11. #11
    DIY Junior Member munhann's Avatar
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    Sorry not details given. Below are ideal IR transmitter design stage; But after i build up whole IR transmitter circuit, i found that IR LED no voltage due to Q2 Transistor Emitter no voltage (Base and Collector have nearly same to 2.5v).. i not sure it is design problem or somewhere connection wrongly..

    Operation Mode
    - This circuit only require 3v DC Supply. 3v Lithium used for this design.
    - C4 used for power supply filters purpose.
    - When switch is open, the whole circuit in very low power or sleep mode to achieve low power consumption. Whole circuit only operate mode during switch close mode.
    - IN4002 Diode applied reserve voltage 4v DC to work act ensure current flow in one direction and block the reverse current flow back.
    - IN4148 Diode used for high-speed switching and used to trigger C1 (T1) to be 1 which able to communicate with IR Receiver through matching serial code bits.
    - From the PT2248 datasheet, basic transmitting waveform consists of 12 bits serial data (3 code bits, 3 single short code and 6 keys input code). Carrier frequency is dependent on the oscillation frequency (Fosc) and is given by following formula;
    A= (Fosc/12) Hz
    So in order to get 38Khz, 38*12 = Fosc = ~455Khz (XTAL) must be used.
    - When (TXOUT) in high (1), Q1 transistor (PNP) emitter and base reverse biased so emitter and collector act as open circuit. No current flow into Q2 transistor and LED0 is in Off Mode.
    - When (TXOUT) in low (0), Q1 transistor (PNP) emitter and base forwards biased so emitter and collector act as close circuit. Current flow into Q2 transistor and LED0 is in ON Mode then signal will be transmit to IR Receiver.

  12. #12
    Jack of all trades DonL's Avatar
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    If Q2 has 2.5 Volts on Collector and Base, then the emitter should have about 1.8 volts, and the LED should be on.
    That is if the transistor is a NPN installed properly and is good.

    I would double check the pin out, because it sounds like it is not inserted or pined properly, wrong type or is bad.


    Have a good day.


    DonL
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  13. #13
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by DonL View Post
    If Q2 has 2.5 Volts on Collector and Base, then the emitter should have about 1.8 volts, and the LED should be on.
    That is if the transistor is a NPN installed properly and is good.

    I would double check the pin out, because it sounds like it is not inserted or pined properly, wrong type or is bad.


    Have a good day.


    DonL
    Even if the LED is on and sending out a "carrier beam" at the carrier frequency, doesn't it need to be modulated with some data for the receiver to interpret? I am not saying I know how these remote devices work, but with the capabilties these 2 chips have, it looks like the receiver is going to be looking for something it understands to give an output. To be honest, I have not yet looked at the Attiny 2313 device to see what it is and what type input it looks for. A demodulator? I will look.
    I am definitely not a pro plumber, but I am a pro crastinator

  14. #14
    DIY Senior Member BobL43's Avatar
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    OK, I looked: Attiny 2313: http://www.atmel.com/dyn/resources/p...s/doc2543S.pdf
    It is a microprocessor that needs a compiled program loaded into it. Perhaps with an "empty brain" it knows not what to do. Did you load a program into it munhann? did you look at any of the stuff you built with an oscilloscope as Don suggested?
    Interesting stuff, but at my age, 68, it is just that to me: interesting. I wish I knew more to help you.
    I will follow this thread, but at this point I cannot contribute much except google search hits :-) I used to work with lots of discrete component linear and digital circuits, and then on to IC circuits, but that was a LONG time ago.
    I am definitely not a pro plumber, but I am a pro crastinator

  15. #15
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by BobL43 View Post
    Even if the LED is on and sending out a "carrier beam" at the carrier frequency, doesn't it need to be modulated with some data for the receiver to interpret? I am not saying I know how these remote devices work, but with the capabilties these 2 chips have, it looks like the receiver is going to be looking for something it understands to give an output. To be honest, I have not yet looked at the Attiny 2313 device to see what it is and what type input it looks for. A demodulator? I will look.

    Yes Bob You are correct.

    The fact that the transistor is not conducting is the first problem.

    That needs to be corrected first. There could be other problems also.

    When a sub part is used, then the EBC pins are sometimes swapped, depending on the Package type and manufacture.


    Have a Great day.


    DonL
    Theory only works perfect in a vacuum.

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