My first simple electronics project

Discussion in 'The Projects Forum' started by asdasd12345, Oct 5, 2006.

  1. asdasd12345

    Thread Starter New Member

    Jul 24, 2005
    Hello. I am new to electronics. I want to build a very simple piece of equiptment. What I want to build is a transmitter that you can listen to on any radio reciever that sends out a beeping noise, but as you get closer to the reciever the beep gets faster and faster, and as you get further away the beeps are spread apart longer. Its a lot like that beeping device from that movie Aliens. Anyway, it sounds like a simple thing to do. Does anyone know how I would get started? I can build a simple receiver that transmit my own voice over a short distance.
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    Well, it's simple in the movies...

    Uncle Charlie (the FCC) does not like or approve of unlicensed transmitters operating on commercial broadcast frequencies.

    There's the question of universality also - AM, FM or digital? No transmitter can do all three (or any two).

    How does the transmitter know when it gets closer to the receiver so it can start to beep faster? Since it's supposed to be on a broadcast band, which receiver does it interrogate? There may be thousands in range.
  3. pebe

    AAC Fanatic!

    Oct 11, 2004
    Hi asdasd.
    I think you will find that in the type of setup you are talking about, it is the receiver that senses the changes in received signal strength of the transmitter and generates a tone accordingly.

    The transmitter can be AM, FM or carrier only. As long as it is powerful enough for the receiver to respond to the changes of signal level, it does not matter.
  4. Chris Wright

    Well-Known Member

    Jul 26, 2006
  5. asdasd12345

    Thread Starter New Member

    Jul 24, 2005
    yeah thats it! only instead of it becoming louder, as you get closer to the reciever, the beeps get faster until its one continuous sound. perhaps i am thinking things are a lot simpler than they are however.
  6. Gadget

    Distinguished Member

    Jan 10, 2006
    A sensing circuit in the receiver determins the strength of the RECEIVED signal (ie higher strength, closer proximity) and this is used to change the beep speed.
    The transmitter has NO WAY to determine the strength of the signal (proximity) in the receiver.
    No matter how you look at it, to do what you want to do would require modifications to the Receiver........
  7. asdasd12345

    Thread Starter New Member

    Jul 24, 2005
    do u think this project is too hard for a beginner? will i need to know complex mathematics to work out how to do it? i imagine the first step would be to work on a way to transmit a signal, that only the special reciever could understand, and then have it somehow work out how strong the signal is and change the tone based on that? something like that.
  8. Gadget

    Distinguished Member

    Jan 10, 2006
    The transmitter would be the easy bit. For short range perhaps a kitset FM bug circuit, or an xtal locked unit if stability is an issue.
    The receiver would be a little more complex, and probably the cheapest way would be to obtain a cheap FM receiver with a Strength Meter, so that the signal to the strength meter can be modified to control your beeper circuit.
    The beeper circuit might be some sort of low frequency Voltage Controlled Oscillator (controlled via the buffered/amplified voltage from the strength meter circuit) with a square wave output driving a piezo sounder.

    All just Ideas that I'm throwing out to you that may or may not help.
    Not what I'd expect a Beginner to tackle.
  9. abiallan

    New Member

    Oct 31, 2008
    well i am not good at electronics but tat link was great and hats off:D
  10. Audioguru

    New Member

    Dec 20, 2007
    You can buy a simple transmitter/receiver that beeps when your kid who is wearing the transmitter gets too far away from you with the receiver. But usually it beeps when the kid wanders behind a nearby metal shelf.
  11. Wendy


    Mar 24, 2008
    If you actually build something like this (the variable beep duration is a non starter) get back with us, we can help with things like directional antennas. The kit ideas are good ones, since any kit you buy locally will likely be legal in your country of origan.
  12. floomdoggle

    Senior Member

    Sep 1, 2008
    Hey asdasd,
    Try a search on "Theremin" An old electronic device that uses an antenna and your body's grounding to produce a circuit. Good place to start if you want to understand how it works.
    Lotsa luck,
  13. jasbone123

    New Member

    Sep 12, 2009
    I read your thread.I am also new to electronics but I think we should check some manuals regarding to the transmitter development.I have search some papers on the net about this and I got confused about making this.I couldn't find the proper modulation technique but I decide to go with AM for practice.