Building an RF remote control

The easiest solution would be to take a cheap wireless toy car take out its receiver module along with its remote and use them in your robot. The other way round is this to make your own RF remote .

We will be using ASK (Amplitude Shift Keying) based Tx/Rx (transmitter/receiver) pair operating at 433 MHz. The transmitter module accepts serial data at a maximum of XX baud rate. It can be directly interfaced with a microcontroller or can be used in remote control applications with the help of encoder/decoder ICs.

RF Receiver Transmitter Module

The encoder IC takes in parallel data which is to be transmitted, packages it into serial format and then transmits it with the help of the RF transmitter module. At the receiver end the decoder IC receives the signal via the RF receiver module, decodes the serial data and reproduces the original data in the parallel format.

 

RF communication flowchart

 

Now in order to control say a dc motor, we require 2 bits of information (switching it on/off) while we need 4 bits of information to control 2 motors. HT12E and HT12D are 4 channel encoder/decoder ICs directly compatible with the specified RF module. The schematic is as shown below.

 

RF transmitter

RF receiver

 

In order to drive motors, we would need to connect a suitable motor driver at the output of the decoder IC. The motor driver circuit can consist of a relay, transistorized H-Bridge or motor driver ICs like the L293D, L298 etc. 

The example above shows the receiver section using the HT-12D decoder IC for a 4-bit RF remote control system.  Similarly the transmitter and receiver module can also use the Holtek 8-bit HT-640/HT-648L remote control encoder/decoder combination for an 8-bit RF remote control system.

 

Driving a motor through NPN

Driving a motor using PNP

 

Here we have used a flyback protection diode to prevent the damage of the diode. The data output of the decoder ICs should be connected to base of transistor (as shown in the figure).

Tip: Also note that we can also use a Darlington pair ULN2803, as it will provide higher voltage and eliminate the need of flyback diode (as it has an internal diode for protection.

 

Download the datasheets of encoder/decoder -

 

 

  

Comments

Member since:
15 March 2009
Last activity:
8 years 18 weeks

Also how are decoding the data at the receiver end... 

Member since:
15 March 2009
Last activity:
8 years 18 weeks

probably the connections should be all right.. just crosscheck by transmitting only 1 bit at a time to verify the code... 

What is the maximum baud rate till which the radio transmitter and receiver works???

i m directly connecting the Tx pin of the microcontroller to the data pin of the radio transmitter with the ground and 5V Vcc in place...Is there anything wrong in the connections??

Member since:
15 March 2009
Last activity:
8 years 18 weeks

Why we only use TX/RX with frequencies 434MHz and 315 MHz only, why other frequency TX/RX pairs are not available... 

Member since:
15 March 2009
Last activity:
8 years 18 weeks

ya if i can do by any means encoding and decoding by programming or any other meansusing AVR,,, instead of using seperate ICs 

Member since:
21 February 2009
Last activity:
7 years 39 weeks

Do you want to use two AVR µCs instead of encoder and decoder?

Member since:
15 March 2009
Last activity:
8 years 18 weeks

reply botskool 

Member since:
15 March 2009
Last activity:
8 years 18 weeks

Please anybody could reply to my query...

Member since:
15 March 2009
Last activity:
8 years 18 weeks

Inducting anteena.. just take a connecting wire used for connections in breadboard...roll it in shape of spiral..it will work absolutely fine... A snap for your refrence... The red wire bulging out nera the receiver is the anteena...

 

What kind of antenna this ask rf receiver module A-434 and the ask rf transmitter module A-434 need to work properly as I see from the schematic above?

Thank you.