RF transmission to transmit data from uC

Discussion in 'Wireless & RF Design' started by ssm14293, Jul 14, 2011.

  1. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    Hi i am new to rf modulation. i want to transmit data via UART mode of 18f452 from one ic to another. maximum range is 100m. please advise me a curcuit to do so. frequency should be below 80mhz and above 10mhz.

    Please dont advice to buy a transmitter module as itx not available in my country, also dont tell me to import because the module would not cost me as much as the importing duty and other stuff might cost me....
    do help me... my whole project depends on it!!

    also do advise a receiver circuit with it... :D

    Thanks in advance!!
     
  2. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    Anyone?? hello??? :(
     
  3. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    if no one can help with that... then tell me if i can connect an fm transmitter to the PIC to transmit dtmf tones... if yes... den how??
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    Thanks for the reply....
    i would like to make a transmitter on 6MHz and its receiver... the ques is how??
    please advice a circuit diagram...

    waiting for your reply!!
     
  6. ssm14293

    Thread Starter Member

    Jul 14, 2011
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  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What will be the transmission speed of the digital data?
    You will need to convert the digital data to some FSK signal.
    This page of the EDUCYPEDIA will give you information on digital modulation techniques:
    http://www.educypedia.be/electronics/rfdigmod.htm

    Bertus
     
  8. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    i have set the UART of the PIC to operate at 2400bps.
     
  9. ssm14293

    Thread Starter Member

    Jul 14, 2011
    90
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    thanks for the link... bt i cannot understand anything! :(
     
  10. ssm14293

    Thread Starter Member

    Jul 14, 2011
    90
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    btw... are u telling me bout DTMF way??
    it would be great if there is an answer is for my first question...
     
  11. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    ok... i would now like to change the question as i have found an encoder decoder IC available in my country...
    now i want the transmitter module schematic not of an ISM band bt of an fm band... itx not a crime here as i want to transmit in my home only dat can be around 50m max... it should be 5V power supply as my whole system is built on 5v power supply... do reply!! Waiting!!
     
  12. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    HF circuits are not easy to deal with, especially with the layout considerations. Which country are you living in? 27MHz toy car receivers/transmitters should be easily available anywhere, don't they?

    Have a look at this site:http://radio-control-schematics.blogspot.com/2007/05/27mhz-toy-car-transmitterreceiver.html
     
  13. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    Hi... I posted somthing and it magically disappeared...
    Anyway... I have found a decoder encoder available in my country...Now all I need is a tx/rx circuit... Fm circuit is quite easy make nd its receiver too... mow please tell me it it can b done... Dont worry bout the law.. as transmitting till 100m is not a crime here... and i want to transmit in a home with a max range of 50 meters.. advice me a circuit... and one more thing... it should be working on 5V as my whole project is working on 5V... Waiting for your reply...
     
  14. ssm14293

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    Jul 14, 2011
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  15. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    i have seen it earlier and i dont understand where the data input will be...
    and i want a circuit working on 5V...
    Thanks!!
     
  16. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Well, you'll have to experiment a bit. I'm quite sure the circuits can be adjusted to work at 5V as well.

    A modulation of the transmitter could be achieved adding/replacing the 15p cap with a variable capacitance diode. At the collector of the second transistor in your receiver you should then be able to retrieve your signal, but it will need further treatment.

    Sorry, I know you want a readymade design, but I guess u have to do some experiments.
     
  17. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    thanks man.... but i m not good at this.... can i use an fm band to transmit signal of an encoder?? i have an fm transmitter with a mic, can it be used for this purpose... it does not transmit more than 15m bt that will still work for me. :D
     
  18. praondevou

    AAC Fanatic!

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    Might be worth trying. Do you have schematic of this transmitter?
     
  19. ssm14293

    Thread Starter Member

    Jul 14, 2011
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    unfortunately... no... itx a single transistor transmitter... i'll buy it and let you know... doesnt cost much... compared to what i hv invested in this project... :/
    is it possible though??
     
  20. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I'm more worried about it's frequency stability and not if it's possible to modulate it/adapt to yor needs. There is something else too. You won't have any feedback if you use only one transmitter, did you think about that? Or does it not matter if you loose a bit once in a while? :D
    The sending MC will have no information about what the other MC received...
     
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