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radio frequency circuit design

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by bananasiong, Mar 8, 2006.

  1. mstechca

    mstechca New Member

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    Why do you care?
    Ron, A microcontroller can be a solution, BUT it must be programmed. If bananasiong is willing to spend time programming it correctly, then it may be no problem.

    I am detecting remote signals myself, and all I am doing is making a simple PLL using a 555 timer, 2 XOR gates, and 2 NAND gates.


    I agree 100%. If the frequency is even slightly off, and the bandwidth of the transmitter is not high enough, the range will also drop, and the signal quality will be poorer.


    One way you can do that is to picture the project in your head, and pretend you are the electricity flowing through it.

    A software filter, very interesting :wink:
    BUT, you must understand that if you intend to use the same microcontroller for another application at the same time, you must consider the rom space required for the filter, and subtract that from the total rom space.

    Nigel does have a point. What he is introducing is what is called a "timeout". Assuming that "no signal" or an invalid signal produces a binary 0, If the result is 0 long enough, then you can make the microcontroller go to an error routine.

    BUT

    this will only work if your transmitter transmits a continuous "1" bit.

    If your transmitter transmits a certain tone as a logic high, a PLL should be used to detect the signal.

    and continuously transmitting a "1" can waste power.
     
  2. bananasiong

    bananasiong New Member

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    hi all,

    i just tested these circuits today. the tx works as few days ago, now it give me nice 10KHz square wave.
    but the rx, even there is signal or no signal, it gave a square wave :roll: :roll: it is not a nice square wave.. it seems combination of a few square waves, looks noisy. the rx is not affected by the tx anymore. what's the problem? may it be the LM393?
     
  3. akg

    akg New Member

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    the freq of the 'noise' sq: wave may hold a clue , are u powering the rx with batt or main power supply ?. power ur rx with batt and move the ckt away from wall plugs and other a/c interferences.
     
  4. dave

    Dave New Member

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  5. Roff

    Roff Well-Known Member

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    Duh. :roll:
    Go back a few posts. You'll find that I said that at least twice.
     
  6. bananasiong

    bananasiong New Member

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    currently i'm testing it using a power supply, but battery is suposed to be used.

    oh.. u're right.. i didn't think about other sourse can affect also. can i still use power supply to test? i will tell u all the result after testing it tomorrow.. thanks for all ur helping :wink: :wink:
     
  7. bananasiong

    bananasiong New Member

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    hi all,

    these circuits work. but i found a problem, when the tx antenna goes near to the rx inductor, the rx output gives a 10KHz square wave, that is what i want. but it has to be very close in order to get the signal. i mean the tx antenna has to be very close to the rx coil (less than or around 1cm only). can i increase the range by increasing the supply to the 555 timer? i can't increase the rx supply because i have to fix it in my robot using battery. thanks for all your helping. :D
     
  8. panic mode

    panic mode Well-Known Member

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    your coil could have more than just one conductor. transmitter coil for AGVs using this type of guidance uses frequency in audio range (some 4-5kHz) and cable instead of wire. ends of cable ware terminated so that it appeared as multi turn coil. This part was done before I had chance to take a closer look but I think it was only some 4-5 turns (or conductors in cable). if more power is required to drive the coil you could use transistor after 555 chip. 555 is not very strong, don't stress it too much.
     
  9. bananasiong

    bananasiong New Member

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    sorry. i really don't get the point..
    what is " ur coil could have more than just one conductor"??
    what is AGV??

    and.. the last sentence, u mean i shouldn't increase the supplied voltage to increase the range? then what should i do? and what is the maximum voltage?
    thanks for helping. :D
     
  10. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The max voltage and output current is listed on the datasheet for the 555.
     
  11. panic mode

    panic mode Well-Known Member

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  12. bananasiong

    bananasiong New Member

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    what do u think of this? should i make any changes in the circuit? :roll:
    is there any problem with my receiving coil?
     
  13. revoltage

    revoltage New Member

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    Can the circuit given by ruff be used as a buried wire fence for a robotic lawn mower? The mower has to move inside this wire fence only.

    Thanks
     
  14. moonstreat

    moonstreat New Member

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    I can use this system to communicate with the PLC to PIC?
     
    Last edited: Jan 14, 2010

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