I have some broken small RC car without remote control and I was interesting to hack the H-bridge of these car and connect them to micro controller circuit  in order to make for example a line follower robot or obstacle avoidance robot.

The common circuit of RC car consist of :
1-Receiver circuit which is define the frequency that the car will work on( for example 40Mhz or 27 Mhz).
2-Controller chip (De-Multiplexer circuit).
3-Dual H-bridge circuit for driving two DC motor (one for backward ,forward and the other for the steering).

you can see that from the above picture,  it's a little complicated to find the base of transistors that will make the motor  work ,also it will take  a lot of time, so instead of that I download datasheet of the controller and from chip pins diagram we can trace the H-bridge pins directly.

RX-2 Controller Chip:
RX-2 is a five function receiver chip work as a De-multiplexer and the multiplexer of this chip called TX-2 which is located in the remote control of  the RC car .it's a very interesting IC and compatible with RF and infrared (check attached datasheet ).

Now from the pin  diagram shown in the next picture  you can locate the pins of H-Bride  (PIN 6 ,7 for right and left ) and (PIN 10,11 for backward and forward).
By connecting +5 volt to these pins you will be able to control the motors but be careful don't connect 5 volt to right and left or backward and forward on the same time ,you might burn your circuit (depend on circuit design) .

Now you can remove RX-2 chip and connect the H-bridge pins to a micro controller  but it's better to connect a 330 ohm resistor between them for current limitation.

if you like or find this tutorial useful to you , please vote for it in the Electronics Tips & Tricks contest.
My Regards

<p>i have a controller and its working but i don't know how to connect the wires to the board</p>
<p>sry i have a board</p>
<p>can you help me mr. husham i want to make a rc car. i have abord bu idon't know what to do</p>
<p>I have a rx2b and a tx2b, how can i control two motors with those? (Just turn them on not giving them direction)</p>
<p>Check the RX-2 datasheet attached in this article (page 9 &amp;10 ) ,for example take the output from backward and connect it to one transistor connected to the motor .</p><p>just search this in Google (control motor using one transistors).</p>
<p>i want to made a rc car circuit not controler</p>
<p>i want to made a rc car circuit not controler</p>
<p>i want to made a rc car circuit not controler</p>
<p>i want to made a rc car circuit not controler</p>
<p>Mr. Hisham, good hack. I have receiver and transmitter in good shape still working. Is there a way to modify it to control speed ? I mean fix one motor on a pot to change the speed of the other one. then we get one motor only but with speed control ? is it possible?</p>
<p>Sir can u give me circuit of this model</p>
<p>In my RC there's also at least one H-Bridge, but another chip. Its a Nikko 20610 i guess, but can't find datasheets etc for that.</p><p>How can i determine, which pin is which? The layout is single layered, so all connections could be seen on the backside</p>
<p>Hi</p><p>I couldn't find any data sheet for this chip ,so try to trace the connection from the Motor-----Transistor-------chip</p><p>you might find a resistor in the way .</p><p>this is the required route to start the H-Bridge. </p>
I'd replaced with L293D
yes I use L293D and it is a power full H-bridge chip but it's not easy to find in my country that's why I am looking for more options from electronic scarab. <br />
<p>plz help me.</p><p>I want to change h bridge by L293d and i d not know how?</p>
<p>Hi</p><p>Read the info in below link carefully ,it will help you to understand how to connect L293D ,make sure that your DC motor take small current .</p><p> http://www.cambierobotics.com/HTML/Robotics/L293%20Motor%20Driver%201.pdf </p>
<p>thank you</p><p>can i ask another question ?</p><p>I am student and my graduation project on robot vehicle by rx-2b.</p><p>so can you help me ? </p>
<p>Plz help me in yours above circuit where the output of receiver is connected ? </p>
<p>Each output of the receiver chip connected to a resister then to the transistor base of the H-Bridge.</p><p>I ignore the receiver chip and connect 4.5 volt with a resister in the way to the H-Bridge.</p><p> Do a search about H-Bridge to understand how it works.</p>
<p>I have a new bright Monte Carlo but with a different chip then the RX-2 (see picture). Any idea how to connect this one?</p>
<p>The problem that there is no number mentioned for this chip so it difficult to get the data sheet. </p>
how can i make a remote control for this chip <br>
you can download the RX-2 data sheet attached in this article ,it might be useful to you.
I am planning to buy a new DC motor driver board which can run 5amp motor but I don't know how to connect it with Atmega 8A chip. Please see the pdf I attached for Atmega 8A.<br> <br> Here are the 7 pins in DC motor controller:-<br> <br> Pin No. Pin Functionality<br> 1 GND Ground<br> 2 IN-1 Logic input for the motor direction.<br> 3 Diagnostic 1<br> (DG-1) Output pin with logic 1 output in normal operation. Represents side of the internal<br> H bridge corresponding to IN-1. Pin is pulled to logic low by the motor driver in<br> case of over temperature or overload due to short circuit.<br> 4 PWM Used to apply Pulse Width Modulation to control motor velocity<br> 5 Diagnostic 2<br> (DG-2) Output pin with logic 1 output in normal operation. Represents side of the internal<br> H bridge corresponding to IN-2. Pin is pulled to logic low by the motor driver in<br> case of over temperature or overload due to short circuit.<br> 6 IN-2 Logic input for the motor direction.<br> 7 CS* Current Sense output to measure the current flowing through the driver
can you show me the design of this circuit please
If you are asking about transmit/receive circuit ,I attached the PDF datasheet which is contain all the circuits.but if you mean the H-bridge circuit I suggest you to use L298D dual H-bridge driver ,it can drive two DC motor from one single chip..
1- why did you use the transmit circuit must it be in the remote contro? <br />2- what is the difference between the two circuits in the picture.i see that contains the same parts with limit components are they equals ? <br />3- what is the type of these transistors ? <br /> <br />4- what is this component ( i attached the photo ) <br />Thank you Eng. Husham Samir
Hi Bassem <br />1- I didn't use transmit circuit but i'm just saying if you are interesting in TX2/RX2 chip you can read the attached data sheet. <br />2- the two circuit will do the same function but with different design <br /> for the small component circuit there is no safety in this design ,so if you made a mistake by connect positive for forward and backward in the same time you will burn the circuit. <br />check below web site for H-bridge design. <br />http://talkingelectronics.com/projects/H-Bridge/H-Bridge-1.html <br />3- 8550 PNP , 8050 NPN <br />4- ferrite cores variable inductor . <br />
ok i will make the design number 2 <br />1- have i do this circuit twise the firsit ( forword &amp; backword ) and the second <br />(right &amp;left) ? <br />2 - have i connect the two lines A &amp; B to the RX2 ? <br />3 - which one of A&amp;B (backword and forword ) ? <br />sorry about my many quetions
1- yes you should make two circuit, that's why I suggest you to use L293D or L298 because with one IC you can control two DC motor . <br />2- if you want to make H-bridge circuit only , no need for RX-2 . <br />3- well it depend on how the polarity of motor connected (up to you). <br /> <br />

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