Saturday, 12 May 2012

434MHz RF modules with encoders and decoders

To make any wire less circuit with less cost we all ways go for RF modules and encoders and decoders .i'm working on HT12E and HT12D.

RF MODULE 
As we know that RF communication is better than IR.Range of RF is more than that of IR at the avilable power. Generally an RF module is used for such wireless communication.This RF module comprises of an RF Transmitter and an RF Receiver. The transmitter/receiver (Tx/Rx) pair operates at a frequency of 434 MHz.Other frequencies are also available (but not in the local Indian market). An RF transmitter accepts serial data and transmits it wireless through RF through its antenna connected at pin4. 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.



We can establish a serial communication between the modules or we can go for encoders at the Tx unit and a decoder at the Rx unit
These are 12 bit encoder and decoder pair available .8bits are assigned for address and 4 bits are for data.There are other pairs available like HT640 encoder ,HT648L decoder(10 bit for address and 8 bit for data).but in Indian market it is hard to find these two.but (HT12E & D) are available every ware.
the pin diagram of the ICs  will be as follows


A0 to A7 bits are used for address bits.To achieve proper communication the 8 bit address at the HT12E of transmitter must match with the HT12D at the receiver an external resistor must be connected between "OSC1 & OSC2" for  rc oscillator.750Kohm at HT12E and 33Kohm for HT12D.

HT12E has a transmission enable pin (pin 14)which is active low.which must be kept low during transmission.in a similar manner HT12D consisting of  Valid transmission pin(pin 17). which goes high on reception of a valid signal from the transmitter.so better to connect an LED for indication but the voltage at this pin may not sufficient to drive an led.so a BC548 transistor can be used. For configuring the address a DIL switch is used.it is an array of switches.
  

THE CIRCUITS


RF TRANSMITTER: the R2 resistor in the transmitter circuit is of 750Kohm. As this particular value is not available i prefer  to use 680Kohm+68Kohm = 748Kohm

PCB LAYOUT OF RF Tx


RF RECEIVER CIRCUIT
 RF Rx PCB LAYOUT

 ANTENNA
 I prefer to use an old model TV antenna.which is very cheep.i bought it for
38 rupees in an electronics store.it consist two antenna poles.remove the plastic holder and separate the two antennas.so that one can be used at transmitter and other can be used at receiver

while using the RF modules better not to go for supply voltage more than 5v.though for some it may be around 12V.as voltage increases heat desipated fby the module increases.that may cause improper function.

working video of robot racer without microcontroller


28 comments:

kick ass said...

Thank you for such great info..!
Can I use this circuit for driving 4 motors?
(they would be paralleled,so 2 motors)
Can u give me some more info..!
Thankyou..! :)

VAMSI DANDA said...

yes i did the project
check out the" high speed racer " project
you can use L293D OR L298 OR realy H-bridge driver

AYUSH SRIVASTAV said...

i'm not able to find TLP434A for the circuit..
please help me with it please

AYUSH SRIVASTAV said...

though i am getting one on ebay. but i'm not sure whether to trust ebay for electronics or not.. please help me out with this !!!

VAMSI DANDA said...

these RF modules are available as a pair.
you can use any RF modules from any company because all are bit compatible.you can find them in any hobby project shop for less than 400Rs

panchal pratik said...

hey buddy can i use these modules without encoder and decoder and with 8051 controller.?? is it possible.?

VAMSI DANDA said...

yes by using serial UART you can do.
but the baud rate must be less than 9600
better to go for 4800 or 1200 as per the data sheet
but there will be a lot of signal noise
some times you may not get the signal

if you want to go for serial communication i prefer you to go for transverse instead of these RF modules for better communication

Akshay said...

which software did you used for making pcb layout?i also want to make layout of simillar project..please reply asap.

VAMSI DANDA said...

i use eagle 5.11

Akshay said...

ok..can u tell me library used for RF module and Encoder, decoder? and thank you for reply.
my project link is as below:
http://www.engineersgarage.com/electronic-circuits/wireless-rf-remote-control-circuit

VAMSI DANDA said...

i just used pinheads

Akshay said...

ok Thank you,I will try..

Shrikanth said...

Sir
I want to use 3no 433MHz RF Tx & Rx. separately
But the problem If i connect to 9 Volt supply to the all 3 Tx then the receivers will not receive its signals.If i disconnect supply for 2 Tx then its particular receiver receives the signal. Pl. help me
Thanking You
shrikanth

VAMSI DANDA said...

here comes the concept of "co channel interference"

are you using encoders and decoders along with RF modules?

Nitin Purohit said...

Hello sir,
i am working with this project,but am not getting any signal on the output of TWS 434,i checked it on an spectrum analyzer.I am working on this since last week,but not getting the output.

yogesh rao said...

am interfacing ht12e and the tx ...this forms the transmission side...ht12d,8051,dc motor and the reciever form the reception side...... pls help...

Nitin Purohit said...

Hello,
can u please tell me how u designed the pcb in eagle.i am unable to make tws rws pair in tht.

akheel mohammed said...

Hi, i have done with the complete circuit its working fine but only one issue. when i power up both the circuit the led's remains on when i press the switch its off. iam not getting the actual problem is. could u please help me in this as i have completed my entire circuit but only for this reason iam stucked PLS HELP ME.............

bristo said...

hi,can i use rf module 433 instead of 434

flt cdt karan chauhan said...

can u tell me something about wireless vedio transmission as well as receiver

Mandeep Sharma said...

yes i did the project
check out the" high speed racer " project
you can use L293D OR L298 OR realy H-bridge driver

Mandeep Sharma said...

sir send the pcb layout of project

Kishan Physics said...

Sir how to know the rf is working or not

mohamed ayad said...

sir can you send me more information on transmitter..

Prashnat Mourya said...

what are the resistor and capacitor value of transmitter ckt and dimension of the pcb?

Unknown said...

Hi Vamsi, I need "Eagle PCB library" for Rx/Tx modules....Let me know if you have them

ahmed said...

what means of data

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