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Thread: Help with usinng 434MHz RF Module with HT12E/D without MCU

  1. #1

    Default Help with usinng 434MHz RF Module with HT12E/D without MCU

    Im trying to make a simple remote controle without usng microcontroller. Im using RF Module 434MHz and Encoder HT12E and Decoder HT12D. Im using the basic crcuit as shown in datasheet of RF A 434. Ive alos reffered to the Circuit shown in dis link
    http://www.rentron.com/RF-Remote.htm
    http://www.rentron.com/Files/ht-12e.gif
    http://www.rentron.com/Files/ht-12d.gif
    Encoder and Decoder used is of 18 Pin.

    Ive connected LEDS between Ground and D0, D1, D2, D3 on the Decoder in the Recieving side.
    Im expecting that when I make connection of Ground and D0, D1, D2 or D3 one by one on Encoder in the Transmitting side, then corrosponding LED on the Recieving side would Glow.

    But when I switch power on, then All four LEDS glow together after few seconds, even if Ive not make connection between ground and any of D0, D1, D2, D3.

    Am I making some mistake in the concept that Im not able to realize?

    Ive put LED on the VT pin of decoder and i expect that it should glow only if I make connection between the Ground and any of D0, D1, D2, or D3. But It randomly glows (rather flicker) even without that connection.

    Im sorry If my question sounds silly, but Im new to Robotics, and ive searched for this on the forumns but couldnt find much.

  2. #2
    Super Moderator T-1000 docel's Avatar
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    The LEDs are showing correct output, since the no signal output is high. They will remain high, if you have'nt installed series resistors.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  3. #3

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    do u mean to say that by default, LEDS would glow, and on recieving signal of button being pressed, corosponding LED would stop glowing?

    Also, in the datasheet of Encoder, http://www.rentron.com/Files/ht-12e.pdf , in the in description, it says that the pin A0-A7 can be connectted to the Vss or be left open. But Vss is already ground. So, in both cases, Bit value would remain 0. So how would I define a high Bit Value at it? Would 5V be gud for it? or would it damage it? Though in the Decoder datasheet, it says dat pin A0-A7 of decoder can be connectted to VDD or Vss.

    And 1 more thing, I am unable to interpret the Graph given at the end of the datasheets. Refferring to the Encoder Datasheet linked above, When My VDD is 5V, I move parallel to y axis. But how have we stopped at 1 k Ohm? ie corosponding to osscilator frequency of 3kHz? How have we come to know that Osscilator frequency is 3kHz?

    And if I dont attach an Antenna to my RF 434A Module (during initial testing of system), then approximately, how much distance would it work in?

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    Super Moderator T-1000 docel's Avatar
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    Quote Originally Posted by mohitkhanna3v_infinate
    do u mean to say that by default, LEDS would glow, and on recieving signal of button being pressed, corosponding LED would stop glowing?
    Yes.

    in description, it says that the pin A0-A7 can be connectted to the Vss or be left open.
    This is obvious. Connect to Vss, or leave it open. Since there are only 2 states in a binary......

    And if I dont attach an Antenna to my RF 434A ...
    .....you will blow out the transmitter :!:

    And whats wrong with the graph?
    There are 3 parameters: you determine 2 parameters to get the 3rd. The curve is almost exponential as it is an RC time constant. The C is built-in and you select the R. Now, the Voltage also determines the time constant.
    So, you read the frequency at the point where the R line intersects the x and y cordinate.
    If you study the graph carefully, you will see that the x,y ::V,F. If you trace the 3kc line horizontally, you will read the Voltage for the R value at the intercept.
    Simply put, 3 kc can be arrived at with 820k@3v,,910k@4v,,1M@5v....
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  5. #5

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    Well, I feel that in the datasheet, Vss is ground (ie 0V). and VDD is 5V. So, if i give the A0-7 pins Vss (0V) or keep them open (again no potentail, so 0V), so wats the differentce?

    And I simple want to know that how do i determine the value of Frequency for my RF module to find R. I know V (5V), So now If i Know frequency, I will come to know wats R) Im new, im using RF module for d 1st time>

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    Super Moderator T-1000 docel's Avatar
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    Mohit!
    i have explained everything in my last post.
    Read the datasheets again, carefully. Everything there is clearly written. Just follow the instructions even if you don't understand ![/i].
    I know it is difficult to understand datasheets the first time, but you can, if you read it thoroughly and patiently.
    ....and read my explanation too, again.

    ( ....did you MEASURE the voltage at the Addr and Data pins, in the open condition??
    It is easy to spoon feed you, but it is the wrong way, I feel.
    It is better that you solve these small things for yourself, in the long run
    Forget what you know or think;read what the manufacturer has to say. They can never be wrong!!
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  7. #7

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    i think im getting wat u mean 2 say between d lines. il try again, n ive read datasheet again, may b il read it 1 more time.... but if things dont seem to work, il have 2 disturb u again.

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    Super Moderator T-1000 docel's Avatar
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    Sure
    No problem!!!!!
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

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