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:
7 years 36 weeks

Just connect the encoders data pins to any of the four data pins of parellel port.. through a buffer (ULN2003) to protect the parallel port from any of the reverse voltage fluctuations.. Here is a circuit for you...

 

You can also directly connect parallel port via diodes, ULN2003 is not very essential.

 

Regards

Aditya Sharma

http://robozeal.blogspot.com

Member since:
4 July 2009
Last activity:
7 years 42 weeks

if we want to interface the txr ckt with pc through parallel port then how to do  this

Member since:
24 March 2009
Last activity:
7 years 37 weeks
Member since:
27 June 2009
Last activity:
7 years 43 weeks

what is the type of antenna to be used and what is the range it can transmit..

can we make antenna or we have to buy it

pl help

Member since:
21 February 2009
Last activity:
7 years 5 weeks

Yes a remote-controlled toy car has a Tx/Rx pair and that pair can be very well taken out from the toy car and used in robotics.  If you are short of time and you have to participate in some competition its the best solution. There is a proper circuit with everything ready to use of Tx/Rx. Remote of the toy car can be used as it is and a Rx chip can be taken out from the car. The price of such a toy car will be around Rs 100 in market. 

Member since:
15 March 2009
Last activity:
7 years 36 weeks

Please answer my queries if anybody can... 

Member since:
15 March 2009
Last activity:
7 years 36 weeks

Does the toy car contains the same kind of TX/RX pair.. 

Member since:
21 February 2009
Last activity:
7 years 5 weeks

All your queries have been answered in the forum. Follow this link

Member since:
15 March 2009
Last activity:
7 years 36 weeks

According to your problem, anteena seems to be the only culprit.. 

i hv connected the data pin of the receiver to the Rx pin of another microcontroller and shorted the ground of the receiver with the ground of the microcontroller...

i m doing simple serial communication with 1 stop bit,8 bit data, no parity bit at 9600 baud rate..

both the microcontrollers hv been configured for these same settings.

maybe there is something wrong with the antenna because when i put the transmitter within one foot of the receiver it works..

help please..