The very first remote control cars were introduced commercially into the market by the Italian Company Elettronica Giocattoli in the mid-1960s.
Engineering students often make small electronic vehicles for college events and competitions, but there are many hobbyists too who like to make these. Making a remote-controlled (RC) vehicle that is wireless is no doubt a little difficult and time-consuming, but it is worth the effort as you do not have to tail it while driving like in the case of wired robot cars. Here, we will be giving you the instructions for building a basic RC multi-terrain vehicle with no complex circuitry. You can try these out to learn the basics of robotics or to just impress people with something that you built yourself. Even though these instructions are for beginners, it is advisable that you have some basic working knowledge of electronics before attempting to follow these instructions. We would especially suggest that you study basic circuit debugging and soldering techniques of electronic circuits before starting.
Following are the components you will require for building an RC car:
- DC geared motors, 4 Nos.
- Wheels, 4 Nos.
- Metallic chassis, 1 No.
- SN754410 motor driver IC, 1 No.
- DPDT switch, 2 Nos.
- HT12E encoder IC, 1 No.
- HT12F decoder IC, 1 No.
- RF Rx-Tx module, 1 No.
- 12V, 9V, and 5V battery packs, 1 No. each
- Screws, screwdrivers, and a soldering iron
The DPDT switch, HT12E encoder, and the RF Transmitter are situated on the remote control side, whereas the RF Receiver, HT12F decoder, motor drive, and the motors are located on the RC car. These are two separate circuits and do not come physically in contact with each other in any way. Here is a flowchart to help you understand how the signal is transmitted in both these circuits.
You also need to know the basic ratings of the components that you are using. For this purpose, you will have to access the datasheets of these components. You can find these sheets online; just google the name of the component, and you will find numerous links. There will be a number of different parameters given in the datasheet, but these are the factors you will have to look for in it:
- Input voltage and current
- Operating temperature
- Logic level
- Pin description
- Timing diagram
- Application circuit
Step 1: Mount the Motors
Mount all the four motors on the chassis with the help of screws, and then just slip the wheels on the shafts of the motor. Make sure that there is no slippage.
Step 2: Motor Connections
If the motors are not previously wired, solder some wires on them. Connect these wires to a power source and excite them. Mark the direction that they spin in for a given polarity. Once you have marked all the four motors, short the terminals of the motors on the same side of the vehicle to make them spin in the same direction when excited with a particular polarity. Here is a diagram to show you how the motors should look upon shorting. Do this for both the pairs of motors on the vehicle. This way, you will have 4 wires from the entire set.
Step 3: Differential Drive Algorithm
Now, we move on to the direction control. For this purpose, we will be using the SN754410 motor driver IC, which is used to drive the motors in both, forward and backward, directions. Here is a chart for you to understand how the differential drive will be used to change the direction of the RC car. Since we have paired two motors on each side of the vehicle, we will call them left and right pairs, based on the side of the car they are situated on.
|Left Pair||Right Pair||Direction of Movement|
Now, we move on to the actual circuits. You will need a working knowledge of how to read and build electronic circuits for understanding the instructions from this step onwards.
Step 4: Power Supply Circuitry
Given above is the circuit diagram for the power supply of the RC car. The DC power jack is where the power supply has to be plugged in. It has an IC 7805T for regulating the input voltage from 12V to 5V, and the switch is used to turn the car ON or OFF.
Step 5: Signal Receiver Circuitry
Given above is the circuit diagram for the receiver, which is situated on the RC car. It has an RF Receiver connected to a decoder to decode the data sent by the transmitter, which is situated on the remote control. The decoded 4-bit data is given to the motor driver as input logic to drive the vehicle. This circuit completes your RC car. The next few steps will discuss how to build the remote control.
Step 6: DPDT Switch Connections
The remote control will have two DPDT switches meant for controlling the left and right pairs of the motor. Take a wire and short the extreme pins of the DPDT as shown in the image below. This will leave you with 4 used and 2 unused pins left for connections. The unused pins on both the DPDT have been labeled as A, B, C, and D, respectively. These four pins should be connected to the four pins of same names in the transmitter circuit that we will discuss in the next step.
Step 7: Signal Transmitter Circuitry
Now, we move on to making the transmitter, i.e., the remote control. As this will be a hand-held device, try to make it as small, light in weight, and handy as possible. You can power this circuit with a simple 9V battery. Following is the circuit diagram for the transmitter. Notice that there is a connection box labeled "To DPDT switch" here. You will have to connect the terminals from the switch to the connection box by following the correct labels. The last two pins in the connection box, +5V and GND, are for the power supply to the DPDT switch, which you can give through a simple 5V battery.
This was all about making a simple RC vehicle. This will surely get you started in the basics of robotics, and you can move on to more complex circuits that use embedded computers, i.e., microcontrollers. Before you power up and start driving your very own RC car though, do make sure to debug the circuit, as you might end up burning the whole thing in case of even a minor fault.