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.
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