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:
18 February 2009
Last activity:
5 days 23 hours

Hi srikapardhi,

I agree debugging electronics circuits can be really very frustrating at times. 

Why don't you post some video or photographs of your line follower in the forum with a small description about it? It will certainly help others.

Are you participating in some line follower competition? If yes, do keep us posted about your progress.  

Founder and Admin

Member since:
4 September 2009
Last activity:
4 years 50 weeks

hello shashwat,

sorry 4 the delay,

s i can post the snap shot if i have safe guarded the pcb board,in anger that the circuit is nt working, i broke it away and throwed away ,instead i made a line follower and photo vore/phobe.

ill make a new pcb 1 more tym and ill post the snap shot.

thanks 4 ur interest towards my question.

1ce again  sorry 4 late response as i was out of station all these days!

Member since:
2 November 2009
Last activity:
1 week 3 days

if

you are not interested in internal working of the remote control car .. carefully open up the car covering case, identify the outputs of the circuit connected to the motors..now place the terminals of the output to the multimeter and check the output voltage.. most remote ctrl car use precoded timer based motor driver, in simple lang.. the output fed to the motors are switched on and off with regular time interval to vary speed .. (you might not be able to detect diff b/w direct and pwm outputs on multimeter)so if the pwm output can be of any use or if you can modify according to your interpretation, use the pwm output.. (it may also happen that there is no pwm at all).

else

alternative is a bit tedious, firstly identify the decoder on car circuit and the ic number written over it , and also the rest of the ICs, google the ic name, read tutorials and data sheet of the decoder, you will come to know how the signals are received and decoded.. and then you can disconnect and isolate receiver and decoder from timer and motor circuit. Here you go .. now output can be used as per your need .. for eg. say if your micro controller works at 5 v high then you can connect micro controller pins to input circuit transmitter circuit and automate the output at the receiver to drive any relay switch(proper rating) or if you are not so techy simple connect the output to any device (proper rating) say a fan or led light and control it using remote..

is that ok! 

Member since:
18 February 2009
Last activity:
5 days 23 hours

Hello jenniferroque,

Which remote car circuit do you have? And what additional functionality you want to add to it? 

Founder and Admin

Member since:
27 November 2009
Last activity:
5 years 3 weeks

How am I going to add/modify outputs of a remote control toy car?

thanks

 

Member since:
18 February 2009
Last activity:
5 days 23 hours

Hello srikarpardhi,

 

Can you post a snapshot of your rf remote circuit which is not working?  

Founder and Admin

Member since:
4 September 2009
Last activity:
4 years 50 weeks

can you plz suggest me  whether the given circuit is totally correct?no errors?

i hope u have created one rf along with its base from the shown figure .

can u plz provide me with its circuit diagram?

 

Member since:
16 October 2009
Last activity:
5 years 9 weeks

i have only ht600 and ht 604L, how should i connect them?i try connect according to its datasheet then put a relay at the receiver there,but didnt hear it click.i dunno which part i connect wrongly,can u give me the circuit?

thanks a lot..

Member since:
4 September 2009
Last activity:
4 years 50 weeks

i designed a pcb and soldered all the components as shown in the circuit diagram.

 

but the bad thing is that the RF remote is not working for my robot..i checked the circuit for 5 times and found no problem with it in construction or soldering.

 

but ic decoder ic is getting slight hot after connecting the power.

i am unable to find problem in the circuit.

 

i have a doubt that the RF modules A434 are not working even though they are new.

is there any way to test if they are working or not.

or please help me with the circuit...

 

 

Member since:
2 September 2009
Last activity:
5 years 10 weeks

hi guys,

i am currently doin a RC car that is driven by 4 motors.. Rc part is ok but

when i give a command to run in forward it runs in forward even after i releive the switch and same for revrse

i use HT12e and HT12d and 433 mhz rf module.. and NO MICROs