RF communication

During early days of mine as an electronic hobbyist, the wireless communication had always

Wired bot

got me excited . Afterall, who wouldnot grow tired of those tangling wires of wired bot. 😛 So i got the cheapest rf module available in the market, without knowing much about it. 😛

So this is a simple project for the beginners who are going to use rf modules for the first time. Here, the signals are generated by the user via push buttons and is sent to the receiver module kept at a distance.

Let us grasp some basic information on the working of a RF- module.

Rf modules

These RF modules work between 30Khz-300 Ghz. In our case, it’s frequency is around 400Mhz-500Mhz (434 MHz approaximately).  The digital data is represented as the variations in the amplitude of the carrier signal according to the message signal (known as ASK).It receives serial data and transmits it wirelessly through RF through its antenna. The transmission occurs at the rate of 1Kbps – 10Kbps.The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter.

These modules work with the serial data, so we need an encoder to encode the parallel binary key to the serial format and hence, transmitted. Similarly at the receiver end, the encoded message signals received serially is converted back to original parallel binary form. The commonly used ICs for this is HT12 D/E.

Transmitter and Receiver circuit

Following is the schematic of the Tranmitter part.

Transmitter Circuit

Pins:
  • 1-8 for addressing purposes
  • 9- ground
  • 10-13 for inputting the parallel data
  • 17 for actual data pin connected to the transmitter
  • 18 voltage

The encoder encodes the input parallel binary data along with its address. In case of multiple transmitter units, this addressing helps identify which transmitter actually transmitted the data.

The resistor connected between 15-16 is used along with some RC circuit inside to determine the frequency of operation of the transmitter circuit.
NOTE: The parallel input data lines send high signal (logic level 1) by default, so we have to connect PushButtons to the ground to generate 0, when pressed…
Coming to the receiver part:

Receiver Circuit

Pins:

  • 1-8 for addressing
  • 9 – ground
  • 10-13 parallel data output
  • 14 serial data coming from the receiver
  • 15-16 resistance for setting the frequency of operation
  • 17 threshold voltage(remained open
  • 18 voltage

The addressing here matches the address of this receiver unit to determine which transmitter unit send the signals.

Since by default, 1111 will be sent to the receiver unit, we will connect LED according to as shown in the figure. Whenever, any PushButton will be pressed at the transmitter part, corresponding LED will glow.

There should be seperate power supply for Transmitter and Receiver part.

Connecting 9/12 volts to the voltage pin of the transmitter and receiver increases their range considerably.

Here is the video for the completed project :

for the complete description of project:

for working only part:

Thanks a lot..

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About Shantanu Sharma

Currently working as Software R&D member in Samsung R&D India.

Posted on October 17, 2012, in Projects and tagged , , , , , , , , . Bookmark the permalink. 3 Comments.

  1. EXCELLENT

  2. Hi nice post,Ive been looking for a good post on RF TX RX,

  3. niice work ,congratzzzzzzzzz

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