Newbie question on basic FSK/MSK RF data comm.

Discussion in 'Wireless & RF Design' started by tryagain, Jun 9, 2011.

  1. tryagain

    Thread Starter New Member

    Jun 4, 2011
    9
    0
    Hi all,

    I am trying to learn some basic RF comm, but am trying to float above the heavy theory.

    I really just need to send '1' or '0' across about a 300m range, a sort of 'hey your car is being broken into' :eek: when a sensor trips.

    So i've found a bunch of cheap receivers and transmitters and transceivers online - and they all use FSK or ASK modulation. The FSK seems to have better range than the ASK one. But I don't want to use a microcontroller.

    So my question is, how does one produce an FSK modulation (but like really basic 'sending' or 'not sending' data), without a microcontroller?

    What kind of components or ICs can I use to send a very simple signal wirelessly? Is it possible for a beginner, or do I need to get an EE degree first?

    Thanks in advance,

    Daniel
     
  2. geoffers

    Active Member

    Oct 25, 2010
    239
    6
    Hi,
    I'm not an expert on anything realy but as no one else has posted I thought I would! I think you could do somthing with a few 555 timers or similar? Basicly you could use two at the transmit end, one running at half the frequency of the other, transmit one frequency for a 1 the other for a 0, at the recive end you could have another 2 timers with the output from the reciver to the reset of the timers, this could be set up to give you 3 states, 1, 0 or no signal. For example the recive timer could be running at a speed between the two transmit timers, then when the high frequncy is being sent it will be reset before it can trigger, the low frequency would let it trigger so you now have the output for 1 & 0, the second recive timer could be set at half the frequency of the slow transmit timer, so if the signal is lost it would trigger. I hope this makes sense and isn't nonsense? Hopefully someone more experianced will put me right if it is:).
    A pic would involve less components and allow you more scope, its worth trying to learn.
    Good luck, Geoff
     
  3. tryagain

    Thread Starter New Member

    Jun 4, 2011
    9
    0
    Hey Geoff,

    Thanks for the suggestion - I don't understand it, but I do like 555 timers - wouldn't they cycle though? i mean, wouldn't they send like 'on' 'off' 'on' 'off' - they are oscillating timers... but yeah, i have no electronics background, so i don't know anything about dual timer designs.

    yeah, perhaps learning PIC would help. i'll try find a USB PIC programming kit that doesn't look like it was designed for windows 95.

    As a followup, I managed some partial success with AM: that is, since it takes CMOS/TTL level inputs, it just sends my signal across, no problem: 5V for on, 0V for off.

    But yeah, AM is only 50m range, so I will probably still need to switch later to FM. I also fear that anyone with a 433Mhz transmitter will be able to screw with my receiver.

    So yeah. I do have a follow-up question:

    Do you happen to know how to switch different relays based on different received frequencies?

    Is that possible?

    Regards
    Daniel
     
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