Trouble with RF module (ASK 434Mhz)

Discussion in 'Embedded Systems and Microcontrollers' started by allahjane, Sep 19, 2012.

  1. allahjane

    Thread Starter Member

    Sep 19, 2012
    75
    1
    Hello,
    Hey I got this RF transmitter and receiver pair from ebay (Says 434Mhz and ASK modulation)

    http://www.ebay.in/itm/280952855034...:IT&_trksid=p3984.m1439.l2649#ht_1883wt_1139

    Its same as

    https://www.sparkfun.com/products/8950

    I prepared a test circuit on a Breadboard/project board as shown in the Attached Image

    [​IMG]

    on turning on the power the Data Pin on the receiver side Always remains HIGH (+5v) no matter what

    Even when the transmitter is removed from the circuit the receiver give HIGH output at data pin

    I'm using the digital data pin and the ground pin to form the data out circuit as you can see in the figure labeld as data terminals

    However a the data pin on receiver goes to LOW state for a split second whenever i give a +5v to the data pin of the transmitter i.e closing the D switch (this may be due to the fact that I'm using the same power Source for both transmitter & Receiver) after then it quickly becomes HIGH again

    there is no tuning controls available on the pair either

    What am i doing wrong? has the ASK modulation has to do something?


    Please help me
     
    Last edited: Sep 19, 2012
  2. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
    89
    These module can't be used without any uC or Decoder chip like HT12E/D if u want to test u have to use Oscilloscope, testing with LED at Data o/p will tell nothing....
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,395
    1,607
    Looking at the Running TX433 and RX433 RF modules with AVR microcontrollers app from Sparkfun there is a image of a transmitter and receiver "In the last pictures you can see data packets of 4 bytes seen on the oscilloscopes. Yellow signal is from transmission data line(TX) while blue is taken from receiver data line(RX):"


    [​IMG]

    So it seems the receiver data is normally high for no data.

    He's got some good comments on how these things work in the real world well worth reading. You do need to transmit real serial data to receive the same, though a simple square wave may go thru the pair as well for a test application.
     
    allahjane likes this.
  4. allahjane

    Thread Starter Member

    Sep 19, 2012
    75
    1
    THANKS I got it Actually the receiver is highly susceptible to noise in absence of transmission from the transmitter...

    as the author says..
    when transmitter doesn't transmit any data – receiver catches various noises that come from power supply or other sources because receiver likes adjust its input gain depending on input signal level
     
  5. allahjane

    Thread Starter Member

    Sep 19, 2012
    75
    1
    THANKS I got it Actually the receiver is highly susceptible to noise in absence of transmission from the transmitter...

    as the author says..
    when transmitter doesn't transmit any data – receiver catches various noises that come from power supply or other sources because receiver likes adjust its input gain depending on input signal level
     
    ErnieM likes this.
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,395
    1,607
    Good job. Maybe one day you can post your project so we can see the cool thing you're building. :)
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    I've seen these on ebay lately for $3.95 for a PAIR (one TX and one RX).

    They can have issues from the receiver cranking up gain when sending serial high bytes like 0xFF, it's better to use manchester encoding or some encoding type that tries to keep roughly the same amount of 0 and 1 bits over time.

    If you must use serial you can send it in half bytes (send two serial bytes, each is half 0 bits and the nibble you are sending). Or you can send a preamble byte like 0x55 so the receiver can set the gain before the data byte(s).
     
  9. allahjane

    Thread Starter Member

    Sep 19, 2012
    75
    1
    Does anyone know how much time the receiver requires to adjust the gain?
     
  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Less than one byte.
     
    allahjane likes this.
  11. Papabravo

    Expert

    Feb 24, 2006
    10,175
    1,798
    I don't think anybody has one, but maybe Sparkfun can get you one if they still sell the product. BTW this thread is 2.5 years old -- did you notice?
     
Loading...