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Cheap one way RF solution

Discussion in 'Embedded' started by Rohan, Mar 4, 2007.

  1. Rohan

    Rohan Guest

    Hi all,

    I am looking for a CHEAP design for RF communication.
    1. The link has to be unidirectional from one microcontroller to
    another.
    2. The data rate requirement is not a consideration as it is very low.
    3. The communication range is between 20-30 meters with obstacles like
    walls in between.

    I am new to RF so don't know which frequency has what advantages and
    which is cheaper and legal. I am in India.
    I believe I have 2 good options to work with.
    1. 433Mhz
    2. 2.4Ghz

    Kindly suggest which would be cheaper and better suited to my needs.

    Thanks,
    Rohan
     
    Rohan, Mar 4, 2007
    #1
    1. Advertising

  2. Rohan

    Leon Guest

    On 4 Mar, 08:03, "Rohan" <> wrote:
    > Hi all,
    >
    > I am looking for a CHEAP design for RF communication.
    > 1. The link has to be unidirectional from one microcontroller to
    > another.
    > 2. The data rate requirement is not a consideration as it is very low.
    > 3. The communication range is between 20-30 meters with obstacles like
    > walls in between.
    >
    > I am new to RF so don't know which frequency has what advantages and
    > which is cheaper and legal. I am in India.
    > I believe I have 2 good options to work with.
    > 1. 433Mhz
    > 2. 2.4Ghz
    >
    > Kindly suggest which would be cheaper and better suited to my needs.
    >
    > Thanks,
    > Rohan


    The Nordic nRF24L01 will do what you want (and a lot more besides) and
    is cheap.

    Leon
     
    Leon, Mar 4, 2007
    #2
    1. Advertising

  3. Rohan

    Rohan Guest

    On Mar 4, 4:37 pm, "Leon" <> wrote:
    > On 4 Mar, 08:03, "Rohan" <> wrote:
    >
    >
    >
    > > Hi all,

    >
    > > I am looking for a CHEAP design for RF communication.
    > > 1. The link has to be unidirectional from one microcontroller to
    > > another.
    > > 2. The data rate requirement is not a consideration as it is very low.
    > > 3. The communication range is between 20-30 meters with obstacles like
    > > walls in between.

    >
    > > I am new to RF so don't know which frequency has what advantages and
    > > which is cheaper and legal. I am in India.
    > > I believe I have 2 good options to work with.
    > > 1. 433Mhz
    > > 2. 2.4Ghz

    >
    > > Kindly suggest which would be cheaper and better suited to my needs.

    >
    > > Thanks,
    > > Rohan

    >
    > The Nordic nRF24L01 will do what you want (and a lot more besides) and
    > is cheap.
    >
    > Leon


    Thanks..
    nRF24L01 is a Tranceiver. I believe they are more expensive than a
    reciever/transmitter pair? I am not sure. Just asking you guys. Since
    i want a Half Duplex path putting two tranceiver at both ends could be
    more expensive.

    I infer that 2.4Ghz being the most common would be really cheap.

    The data rate on this chip is for VOIP level and my requirement is a
    mere fraction of that. So again this chip seems a little high end for
    my needs.

    Any ATMEL users around?
     
    Rohan, Mar 4, 2007
    #3
  4. Rohan

    Rohan Guest

    On Mar 4, 4:37 pm, "Leon" <> wrote:
    > On 4 Mar, 08:03, "Rohan" <> wrote:
    >
    >
    >
    > > Hi all,

    >
    > > I am looking for a CHEAP design for RF communication.
    > > 1. The link has to be unidirectional from one microcontroller to
    > > another.
    > > 2. The data rate requirement is not a consideration as it is very low.
    > > 3. The communication range is between 20-30 meters with obstacles like
    > > walls in between.

    >
    > > I am new to RF so don't know which frequency has what advantages and
    > > which is cheaper and legal. I am in India.
    > > I believe I have 2 good options to work with.
    > > 1. 433Mhz
    > > 2. 2.4Ghz

    >
    > > Kindly suggest which would be cheaper and better suited to my needs.

    >
    > > Thanks,
    > > Rohan

    >
    > The Nordic nRF24L01 will do what you want (and a lot more besides) and
    > is cheap.
    >
    > Leon


    Thanks..
    nRF24L01 is a Tranceiver. I believe they are more expensive than a
    reciever/transmitter pair? I am not sure. Just asking you guys. Since
    i want a Half Duplex path putting two tranceiver at both ends could be
    more expensive.

    I infer that 2.4Ghz being the most common would be really cheap.

    The data rate on this chip is for VOIP level and my requirement is a
    mere fraction of that. So again this chip seems a little high end for
    my needs.

    Any ATMEL users around?
     
    Rohan, Mar 4, 2007
    #4
  5. Rohan

    Wim Ton Guest

    >
    > I am looking for a CHEAP design for RF communication.
    > 1. The link has to be unidirectional from one microcontroller to
    > another.
    > 2. The data rate requirement is not a consideration as it is very low.
    > 3. The communication range is between 20-30 meters with obstacles like
    > walls in between.
    >
    > I am new to RF so don't know which frequency has what advantages and
    > which is cheaper and legal. I am in India.
    > I believe I have 2 good options to work with.
    > 1. 433Mhz
    > 2. 2.4Ghz
    >

    I suggest 433 MHz, as 2.4 GHz does not travel well trough stone walls in my
    experience. I guess some of the more optimistic numbers for 2.4 GHz come
    from the US,where wall are often made of thin plasterboard.

    Wim
     
    Wim Ton, Mar 4, 2007
    #5
  6. Rohan

    msg Guest

    Rohan wrote:


    > I am new to RF so don't know which frequency has what advantages and
    > which is cheaper and legal. I am in India.
    > I believe I have 2 good options to work with.
    > 1. 433Mhz
    > 2. 2.4Ghz
    >
    > Kindly suggest which would be cheaper and better suited to my needs.


    Hi, I don't know about allocations in India, but in the U.S.
    there is a portion of the 27MHz 'citizen's band' that is used for
    remote control and packet data. A wireless messaging device
    with lots of 'aftermarket' uses by hams and others is the
    Cybiko; it works on 27MHz for distances of up to 1/4 mile, has
    open source software (and closed source development kit),
    schematics, etc. You might also consider 49MHz (also a remote
    control allocation) if permitted in India.

    Regards,

    Michael
     
    msg, Mar 4, 2007
    #6
  7. Hello Rohan,

    What kind of controller are you using? I have some simplex/duplex code for a
    PCA equipped Atmel 8052 that works just as well in a simplex configuration.
    I used super cheap TWS-434A transmitter and RWS-434 receiver modules that
    operate in 1200 bps CW mode. Not too sure about the range, but you should
    get 20m with a brick wall in the way okay. Check my homepage listed below if
    you think that might help.

    --
    32°02'14.23"S 115°53'21.30"E
    http://www.review-a-gadget.com/
    http://members.iinet.net.au/~vanluynm/

    "Rohan" <> wrote in message
    news:...
    > Hi all,
    >
    > I am looking for a CHEAP design for RF communication.
    > 1. The link has to be unidirectional from one microcontroller to
    > another.
    > 2. The data rate requirement is not a consideration as it is very low.
    > 3. The communication range is between 20-30 meters with obstacles like
    > walls in between.
    >
    > I am new to RF so don't know which frequency has what advantages and
    > which is cheaper and legal. I am in India.
    > I believe I have 2 good options to work with.
    > 1. 433Mhz
    > 2. 2.4Ghz
    >
    > Kindly suggest which would be cheaper and better suited to my needs.
    >
    > Thanks,
    > Rohan
    >
     
    Dhr de Luynes, Mar 5, 2007
    #7
  8. Rohan

    skr Guest

    On Mar 4, 1:03 pm, "Rohan" <> wrote:
    > Hi all,
    >
    > I am looking for a CHEAP design for RF communication.
    > 1. The link has to be unidirectional from one microcontroller to
    > another.
    > 2. The data rate requirement is not a consideration as it is very low.
    > 3. The communication range is between 20-30 meters with obstacles like
    > walls in between.
    >
    > I am new to RF so don't know which frequency has what advantages and
    > which is cheaper and legal. I am in India.
    > I believe I have 2 good options to work with.
    > 1. 433Mhz
    > 2. 2.4Ghz
    >
    > Kindly suggest which would be cheaper and better suited to my needs.
    >
    > Thanks,
    > Rohan


    Hi Rohan,

    Atmel has series of Transmitters / Receivers for Automotive control
    i.e. Tire Pressure Monitoring System look at the following link

    http://www.atmel.com/dyn/products/devices.asp?family_id=606
     
    skr, Mar 5, 2007
    #8
  9. Rohan

    David Brown Guest

    Rohan wrote:
    > On Mar 4, 4:37 pm, "Leon" <> wrote:
    >> On 4 Mar, 08:03, "Rohan" <> wrote:
    >>
    >>
    >>
    >>> Hi all,
    >>> I am looking for a CHEAP design for RF communication.
    >>> 1. The link has to be unidirectional from one microcontroller to
    >>> another.
    >>> 2. The data rate requirement is not a consideration as it is very low.
    >>> 3. The communication range is between 20-30 meters with obstacles like
    >>> walls in between.
    >>> I am new to RF so don't know which frequency has what advantages and
    >>> which is cheaper and legal. I am in India.
    >>> I believe I have 2 good options to work with.
    >>> 1. 433Mhz
    >>> 2. 2.4Ghz
    >>> Kindly suggest which would be cheaper and better suited to my needs.
    >>> Thanks,
    >>> Rohan

    >> The Nordic nRF24L01 will do what you want (and a lot more besides) and
    >> is cheap.
    >>
    >> Leon

    >
    > Thanks..
    > nRF24L01 is a Tranceiver. I believe they are more expensive than a
    > reciever/transmitter pair? I am not sure. Just asking you guys. Since
    > i want a Half Duplex path putting two tranceiver at both ends could be
    > more expensive.
    >


    You don't get receiver-only devices. There are transmitter-only, and
    transceiver types. Transmitter-only are now less common - they are not
    much cheaper than transceivers, and it's often nice to have a little
    feedback (blinking LED, for example).

    > I infer that 2.4Ghz being the most common would be really cheap.
    >
    > The data rate on this chip is for VOIP level and my requirement is a
    > mere fraction of that. So again this chip seems a little high end for
    > my needs.
    >
    > Any ATMEL users around?
    >
     
    David Brown, Mar 8, 2007
    #9
  10. Rohan

    larwe Guest

    On Mar 8, 7:27 am, David Brown

    > You don't get receiver-only devices. There are transmitter-only, and


    That isn't even vaguely true. RFMD, Philips, Melexis, Atmel,
    Microchip, ... all make receive-only devices. Not only are they
    cheaper, they're also cheaper to integrate due to fewer and simpler
    external components.

    RKE applications, for instance, have absolutely no use for a
    transceiver.
     
    larwe, Mar 8, 2007
    #10
  11. Rohan

    David Brown Guest

    larwe wrote:
    > On Mar 8, 7:27 am, David Brown
    >
    >> You don't get receiver-only devices. There are transmitter-only, and

    >
    > That isn't even vaguely true. RFMD, Philips, Melexis, Atmel,
    > Microchip, ... all make receive-only devices. Not only are they
    > cheaper, they're also cheaper to integrate due to fewer and simpler
    > external components.
    >
    > RKE applications, for instance, have absolutely no use for a
    > transceiver.
    >


    Fair enough - it looks like I've been over-generalising based on the
    manufacturers we have used. Nordic VLSI, for example, no longer appears
    to have anything other than transceivers. Chipcon (now part of TI) have
    transmitters, but no receiver-only devices. From the way these devices
    are designed, most of the hard work is on the receiving end - you save
    very little by making a receiver-only instead of a transceiver. If the
    quantities are high enough, then of course small savings turn into large
    ones.
     
    David Brown, Mar 8, 2007
    #11
  12. Rohan

    Rohan Guest

    On Mar 8, 6:24 pm, David Brown <>
    wrote:
    > larwe wrote:
    > > On Mar 8, 7:27 am, David Brown

    >
    > >> You don't get receiver-only devices. There are transmitter-only, and

    >
    > > That isn't even vaguely true. RFMD, Philips, Melexis, Atmel,
    > > Microchip, ... all make receive-only devices. Not only are they
    > > cheaper, they're also cheaper to integrate due to fewer and simpler
    > > external components.

    >
    > > RKE applications, for instance, have absolutely no use for a
    > > transceiver.

    >
    > Fair enough - it looks like I've been over-generalising based on the
    > manufacturers we have used. Nordic VLSI, for example, no longer appears
    > to have anything other than transceivers. Chipcon (now part of TI) have
    > transmitters, but no receiver-only devices. From the way these devices
    > are designed, most of the hard work is on the receiving end - you save
    > very little by making a receiver-only instead of a transceiver. If the
    > quantities are high enough, then of course small savings turn into large
    > ones.


    Discussion so far...
    1. 2.4 Ghz vs 433 Mhz - 2.4Ghz is easier to impliment and cheaper but
    doesn't travel through walls well.
    --This is a important consideration. Does anyone has any experience
    with the 2.4 Ghz range issues. Is it possible to increase the range to
    upto 50 meters with walls in between?

    2. Recieve only device is not much of a cost saving: fair enough and
    with rising sales of tranceivers the cost will eventually come below a
    recieve only device.
    --So its better to base the design on a tranceiver device
     
    Rohan, Mar 8, 2007
    #12
  13. Rohan

    larwe Guest

    On Mar 8, 9:38 am, "Rohan" <> wrote:

    > 1. 2.4 Ghz vs 433 Mhz - 2.4Ghz is easier to impliment and cheaper but


    Hardly! Where did you get this information?
     
    larwe, Mar 8, 2007
    #13
  14. Rohan

    skr Guest

    2. Recieve only device is not much of a cost saving: fair enough and
    with rising sales of tranceivers the cost will eventually come below a
    recieve only device.
    --So its better to base the design on a tranceiver device

    ----- Agree Receive functionality is difficult and consume most part
    of
    trans-receiver but not from marketing and selling point of view
    this is true from designing IC point of view.

    You can go for receive only if you need only that

    As Larwe specified RKE application is what your device looks like and
    you
    have IC available for that on Atmel or Maxwell
     
    skr, Mar 9, 2007
    #14
  15. Rohan

    larwe Guest

    On Mar 9, 10:14 am, David Brown

    > > 1. 2.4 Ghz vs 433 Mhz - 2.4Ghz is easier to impliment and cheaper but
    > > doesn't travel through walls well.

    >
    > The price and complexity depends on your application type. I have
    > mostly required two way communication with various types of data,
    > networks of several radio nodes, automatically finding and identifying


    This is not just a Tx/Rx or even a txvr/txvr pair, it is a complete
    network stack! Maybe this is where our logical disconnect is
    occurring.

    If the goal is "transmit a few bytes from point A to point B cheaply"
    then an unlicensed transmitter in the 433MHz or 300-ish MHz (315MHz
    commonly in the USA) region is the cheapest solution. The transmitter
    can be little more than a couple of transistors, an xtal and a few
    matching passives (though it's easier to use an IC solution, which
    makes the BOM one IC, one xtal, half a dozen passives). The receiver
    can be any of several possibilities from Philips, Infineon, Melexis
    etc - Infineon probably one of the cheaper options. A comparator to
    slice the data, and a micro to decode it, and you're away.

    Plenty of people sell canned solutions for this sort of thing, e.g.
    <http://www.rentron.com/rf_remote_control.htm> is a rather cute-
    looking option.

    The FHSS and DSSS 2.4GHz solutions are _very_ complicated to deal with
    (compared with the simple Manchester-on-a-wet-string ASK techniques)
    unless you buy everything canned, in which case they are expensive.
     
    larwe, Mar 9, 2007
    #15
  16. Rohan

    David Brown Guest

    Rohan wrote:
    > On Mar 8, 6:24 pm, David Brown <>
    > wrote:
    >> larwe wrote:
    >>> On Mar 8, 7:27 am, David Brown
    >>>> You don't get receiver-only devices. There are transmitter-only, and
    >>> That isn't even vaguely true. RFMD, Philips, Melexis, Atmel,
    >>> Microchip, ... all make receive-only devices. Not only are they
    >>> cheaper, they're also cheaper to integrate due to fewer and simpler
    >>> external components.
    >>> RKE applications, for instance, have absolutely no use for a
    >>> transceiver.

    >> Fair enough - it looks like I've been over-generalising based on the
    >> manufacturers we have used. Nordic VLSI, for example, no longer appears
    >> to have anything other than transceivers. Chipcon (now part of TI) have
    >> transmitters, but no receiver-only devices. From the way these devices
    >> are designed, most of the hard work is on the receiving end - you save
    >> very little by making a receiver-only instead of a transceiver. If the
    >> quantities are high enough, then of course small savings turn into large
    >> ones.

    >
    > Discussion so far...
    > 1. 2.4 Ghz vs 433 Mhz - 2.4Ghz is easier to impliment and cheaper but
    > doesn't travel through walls well.


    The price and complexity depends on your application type. I have
    mostly required two way communication with various types of data,
    networks of several radio nodes, automatically finding and identifying
    new nodes, retries on errors, and that sort of thing. I've therefore
    been using more integrated devices (which is why I never even knew about
    receive-only devices). There is little doubt that the more advanced
    devices make this easier, as they handle the low-level telegram
    transfers themselves (think of them as somewhat like a CAN controller,
    rather than a UART). These devices first appeared, to my knowledge,
    with 2.4 GHz chips - but there are certainly 433 and 900 MHz devices
    with this sort of functionality.

    If you mean easier from the regulations viewpoint, then you are right
    (as long as you stick to low power) - at 2.4 GHz, you can pick
    frequencies that are available almost all over the world.


    If you are looking for something really simple, then as others have
    suggested, a transmit-only and receive-only pair will be the lowest cost
    for high volumes. Atmel have some 4-bit microcontrollers with
    transmitters for very low prices.

    > --This is a important consideration. Does anyone has any experience
    > with the 2.4 Ghz range issues. Is it possible to increase the range to
    > upto 50 meters with walls in between?
    >
    > 2. Recieve only device is not much of a cost saving: fair enough and
    > with rising sales of tranceivers the cost will eventually come below a
    > recieve only device.
    > --So its better to base the design on a tranceiver device
    >
     
    David Brown, Mar 9, 2007
    #16
  17. Rohan

    Tom Guest

    In article <>, "Rohan" <> wrote:
    >1. 2.4 Ghz vs 433 Mhz - 2.4Ghz is easier to impliment and cheaper but
    >doesn't travel through walls well.
    >--This is a important consideration. Does anyone has any experience
    >with the 2.4 Ghz range issues. Is it possible to increase the range to
    >upto 50 meters with walls in between?
    >
    >2. Recieve only device is not much of a cost saving: fair enough and
    >with rising sales of tranceivers the cost will eventually come below a
    >recieve only device.
    >--So its better to base the design on a tranceiver device


    Something that I've been noticing lately is that 2.4 GHz devices are becoming
    so popular that there is an incredible amout of congestion on that band. You
    didn't mention whether your indoor environment is office or home or industrial
    but if you do decide to go with this band you may have all sorts of other
    devices causing interference like WiFi, Bluetooth, microwave ovens, cordless
    phones, wireless video cameras, just to name a few.

    We recently got a 2.4 GHz cordless phone for the office. Completely useless.
    In a large office building there are so many other phones and WiFi devices
    that this phone would start dropping out as soon as you got more than 2m away
    from the base station. We replaced it with a 900 MHz phone and it's crystal
    clear even at the far end of the office which is about 20 m away.

    The other ISM bands like 433 MHz or 27 MHz have very few devices on them so
    the chance of interference is very low. Probably the biggest users on 433 are
    keyless entry devices and wireless thermometers, while 27 MHz is popular for
    cordless mice and remote control toys.

    In terms of transmit-only and receive-only devices, there are single chip
    modules like these:
    www.rfm.com/products/vwire.htm
    and there are also CPUs with built-in transmitters like the rfPIC12F675 and
    the standalone receiver rfRXD0420. The prices are around $2 - $3 in quantities
    of 100. The transmitter can be made for well under $1 if you're willing to
    invest in some RF design. Take a look at how a typical keyless entry
    transmitter is built. The entire RF section consists of one large PCB trace
    that acts as an antenna, one UHF transistor and a few passives.

    ---Tom.
     
    Tom, Mar 9, 2007
    #17
  18. "Tom" <> wrote in message
    news:ptfIh.12889$4D.11154@pd7urf2no...
    > In article <>, "Rohan"

    <> wrote:
    > The other ISM bands like 433 MHz or 27 MHz have very few devices on them

    so
    > the chance of interference is very low. Probably the biggest users on 433

    are
    > keyless entry devices and wireless thermometers


    Not to mention radio amateurs that are allowed to produce 400 Watts in the
    entire 430 to 440MHz range. If I would go to a gas station and talk to a
    fellow ham on 433,920MHz, which is a perfectly legal thing to do, no one at
    that gas station would be able to unlock his car with his keyfob....

    Meindert
     
    Meindert Sprang, Mar 9, 2007
    #18
  19. Rohan

    Tauno Voipio Guest

    Meindert Sprang wrote:
    > "Tom" <> wrote in message
    > news:ptfIh.12889$4D.11154@pd7urf2no...
    >
    >>In article <>, "Rohan"

    >
    > <> wrote:
    >
    >>The other ISM bands like 433 MHz or 27 MHz have very few devices on them

    >
    > so
    >
    >>the chance of interference is very low. Probably the biggest users on 433

    >
    > are
    >
    >>keyless entry devices and wireless thermometers

    >
    >
    > Not to mention radio amateurs that are allowed to produce 400 Watts in the
    > entire 430 to 440MHz range. If I would go to a gas station and talk to a
    > fellow ham on 433,920MHz, which is a perfectly legal thing to do, no one at
    > that gas station would be able to unlock his car with his keyfob....
    >
    > Meindert
    >
    >


    Otherwise OK, but the international amateur power limit
    on the 430 MHz band is 1 kW.

    The frequency division plan states clearly that these low-
    power devices have no interference protection from the
    legal higher-power services on the same band.

    --

    Tauno Voipio, OH2UG
    tauno voipio (at) iki fi
     
    Tauno Voipio, Mar 9, 2007
    #19
  20. Rohan

    larwe Guest

    On Mar 9, 1:19 pm, "Meindert Sprang"

    > entire 430 to 440MHz range. If I would go to a gas station and talk to a
    > fellow ham on 433,920MHz, which is a perfectly legal thing to do, no one at


    Worse, in the US it is a fairly common thing that military/police
    installations will expand their spectrum usage to cover unlicensed low-
    priority-user bands, and suddenly in an entire neighborhood people
    cannot open their garage doors remotely.
     
    larwe, Mar 9, 2007
    #20
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