DIY Remote Control Car: How to Make Your Own RC Car!
By Mayoogh Girish
Remote control cars have been the dream the toy for most kids. And you can never outgrow them! In this post, I will show you step by step, how to make a simple Remote Control Car that operates in RF (radio frequency). This is a very simple and beginner level robotic project which can be made by anyone with interest. I will be discussing on the working of all integrated circuits (IC) and modules used in this robot. And there is no programming required for making this robot!
- RF transmitter receiver module
- prototype board x2
- HT12E encoder
- HT12d decoder
- L293D Motor driver
- 7805 step down regulator
- 12v dc motor(RPM depends on your choice, I have used 300 RPM)
- 12v power supply
- Robot Chassis (Optional) or try a DIY chassis :D
How Does it Work?
Here we will use a couple of ICs and a motor fixed to a chassis to make a remote control car. The brief idea is to transmit control signals through Radio Frequency and receive it through a receiver module in the car. We will have two switches in our remote control to power each motor of the car. The state of the switches (ON / OFF) is the control data. This data from the remote control is encoded before transmission, received back and decoded again to be sent to the motor drivers. This is achieved using an RF module and an encoder(HT12E)-decoder(HT12D) pair.
This RF module consists of an RF Transmitter and an RF Receiver. The transmitter/receiver (TX/RX) pair operates at a frequency of 434 MHz. An RF transmitter receives serial data and transmits it wirelessly at RF through its antenna connected at pin 4. The transmission occurs at the rate of 1Kbps – 10Kbps. The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter. The RF module is used along with a pair of encoder and decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder.
Using the combination of different states f the two switches, you can control the direction of motion of your remote control car. If both switches are off, both motors will be off and the car will not move. If both are on, the car will move straight ahead. And to turn the car, switch ON only the motor on the side to which the car has to turn.
Making Power Supplies for the Remote Control Car
First we will start with the power supply circuits. Both, the RF transmitter and receiver circuits need separate power supplies. The receiver circuit needs to be powered using 12V supply and transmitter circuit can be powered using 9V battery.
You can see the circuit for the receiver power supply on the right. Using this diagram, wire up the supply circuit. You can also add an LED via a 1k resistor to indicate the state of power supply.
- IC 7805 regulates the 12V supply to 5V. (you can also use a 9V supply here)
- You can also use 0.1uF and 470uF capacitors inthe circuit.
- And 1k resistor for status led.
NOTE: Use heat sink for 7805 because we are dropping 7v (12-5) so lots of heat will be produced to burn the regulator so use of heat sink is recommended.
Making the Transmitter (Remote Control)
The transmitter circuit consists of
- HT12E encoder(Pin Out)
- RF transmitter module(Pin Out)
- Two DPDT switches
- Power supply circuit
- And a 1M resistor
You can see I have marked A, B, C, D in the transmitter circuit after the switch. The same has been marked on the DPDT Switch Diagram. Connect the A,B,C,D on the transmitter circuit to the A,B,C,D on the 2 DPDT switches.
The receiver circuit consists of 3 ICs:
Wire the circuit as per the above receiver schematic. There are 2 LEDs in the receiver board. One lights up when power supply is given to the receiver. The other one near the IC HT12D should light up when power supply is given to transmitter circuit. This provides you with a valid transmission (VT) when power is given at the transmitter. If not, there is something wrong with your connection or your RF TX RX module.
The L293D is a Motor Driver IC. It allows the motor to be driven in both directions. L293D is a 16-pin IC with eight pins on each side, dedicated to controlling a motor. It can control a set of two DC motors at a same time in any direction. It has 2 INPUT pins, 2 OUTPUT pins and 1 ENABLE pin for each motor. L293D consists of two H-bridges. H-bridge is the simplest circuit for controlling a low current rated motor.
NOTE: Use red wires for positive and black for negative. If there are any problems, it will be easier to debug the circuit.
Choosing the Right Motor
Choosing a motor is very important and it totally depends on the type of robot (car) you are making if you are making a smaller one use 6v Bo motor If you are making a larger one which need to carry heavy load then use an 12v dc motor.
Choosing the Right RPM for the Motor
I have used a 12V – 300RPM motor. RPM stands for revolutions per minute. It is the number of times the shaft of a DC motor completes a full spin cycle per minute. A full spin cycle is when the shaft turns a full 360°. The amount of 360° turns, or revolutions, a motor does in a minute is its RPM value. You should be careful not to choose motors of higher rpm because it will be difficult to control. And remember that speed is inversely proportional to torque.
Debugging the RC Car (Only if There is a Problem in the Circuit)
In this section, I will be discussing on how to debug the remote control circuit. First of all, don’t be angry just keep calm!:)
For debugging, we will split the circuit into different sections.
- Place the IC on a bread board.
- Give VCC(5v) and Gnd to the IC and then give the 12v to pin 8.
- Connect the enable pins of the motors to 5v.
- Now give power to the input of one motor and check the output pins with a multimeter.
- If it shows nothing then there is problem with your motor driver. Replace it.
Most problems that arise in the power supply circuit is due to short circuit. So power off the circuit and use a multimeter to check whether there is any connection between negative and positive.
DECODER AND ENCODER(HT12E/Ht12D)
For debugging the decoder and encoder IC:
- Connect pin 7 of HT12E to pin 14 of HT12D
- Connect push buttons at pin 10,11,12,13 of HT12E and connect 4 leds at pin 10,11,12,13 of the decoder (connect as per Debugging circuit figure).
- The led should light up when switches are pressed. If it doesn’t, then there must be a problem with the RF module. Try replacing the module.
That’s it. Assemble the motors, circuit and wheels on the chassis. Rev up your motors and show your DIY remote control car to your kin folks and friends!! :)
Watch the robot in action here: