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
Husham
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
Husham
RX-2 Datasheet.pdf171 KB
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Here are the 7 pins in DC motor controller:-
Pin No. Pin Functionality
1 GND Ground
2 IN-1 Logic input for the motor direction.
3 Diagnostic 1
(DG-1) Output pin with logic 1 output in normal operation. Represents side of the internal
H bridge corresponding to IN-1. Pin is pulled to logic low by the motor driver in
case of over temperature or overload due to short circuit.
4 PWM Used to apply Pulse Width Modulation to control motor velocity
5 Diagnostic 2
(DG-2) Output pin with logic 1 output in normal operation. Represents side of the internal
H bridge corresponding to IN-2. Pin is pulled to logic low by the motor driver in
case of over temperature or overload due to short circuit.
6 IN-2 Logic input for the motor direction.
7 CS* Current Sense output to measure the current flowing through the driver
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 ?
3- what is the type of these transistors ?
4- what is this component ( i attached the photo )
Thank you Eng. Husham Samir
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.
2- the two circuit will do the same function but with different design
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.
check below web site for H-bridge design.
http://talkingelectronics.com/projects/H-Bridge/H-Bridge-1.html
3- 8550 PNP , 8050 NPN
4- ferrite cores variable inductor .
1- have i do this circuit twise the firsit ( forword & backword ) and the second
(right &left) ?
2 - have i connect the two lines A & B to the RX2 ?
3 - which one of A&B (backword and forword ) ?
sorry about my many quetions
2- if you want to make H-bridge circuit only , no need for RX-2 .
3- well it depend on how the polarity of motor connected (up to you).