Build your own Remote Control (RC) Car
In this tutorial we will learn how to build a simple wired remote control car. Building your own simple yet powerful wired robot is the first step in the field of robotics.
To begin building your car you first need to decide few things about it. What kind of steering you want? In this tutorial we will build a differential drive car.
A car has mainly five things viz. tyres, motor, chassis, axle and remote controller. A chassis can be made of anything which is flat, light, flexible, hard, and easy to cut like Toughened Styrofoam, Acrylic sheet, plastic tray, etc. Now we should select our tyres. Tyres should also be light in weight so that they do not put extra load on motors. Tyres can either be made by wood or plastic or could be purchased from market. We would require at least four wheels. You can add more wheels depending upon your car’s dimensions. We can use tyres of any appropriate size. You can even use pram wheels or bicycle’s side wheels. Once you have selected tyres you will need axle to support your tyres. A steel rod or aluminium rod of appropriate diameter can be used. Just take care that the rod fits properly in the tyre and tyre is not slipping over the rod. Now you need to select the most important part of your car i.e. motor. An internal or external geared D.C. motor of 12V or 24V rating is best available in the market. You can select the speed of motor depending on the track where you will run your car. If you select a motor with high speed then it will provide less torque and if you select a motor with high torque then its speed will cripple. An appropriate range of motor speed is 100–200 RPM. If you plan to run your car in mud, dust or sand then you should prefer an internal gear system to avoid jamming of gears with mud. We would require at least two motors. You can even use four motors if you wish to provide more power to your car. All the motors should be perfectly identical.
After you selected and collected all the required material for your car you are almost half the way to run your car. Now it’s the time to assemble your car. If you are using two motors on front wheels then make your rare wheels free to rotate with the help of ball-bearing. Assemble one motor on right front wheel and other motor on left front wheel. Mount both the motors and tyres on the chassis with the help of nuts and bolts. Once you assemble your car, check that it is moving freely. If the car is not moving freely then align all the tyres again so that they are free to rotate. So now the mechanical work of our car is complete. Now we have to make it run on electricity and control it via remote control. For this purpose we will use differential drive. Before building a differential drive, you should know how it works. If you already know about it then you may skip the next paragraph.
Differential drive is the easiest way to make your robot steerable. In differential drive system we mount one motor with right wheel and other motor with left wheel. When both the motors are rotated in forward direction the car moves forward. When both the motors are moved in reverse direction, the car moves backward. If we rotate right motor in forward direction and left motor in backward direction a torque is produced in anti-clockwise direction and the car turns to left. Similarly if left motor is turned in forward direction and right motor in reverse direction the torque is produced in clockwise direction and car turns to right. This is all about differential drive. With differential drive we can rotate our robot by 360 degree at a single point.
To change the direction of motor we need to change the polarity of supply. This can be done using H-bridge circuit. An H-Bridge circuit can be made using four SPST (Single Polarity Single Toggle) Switch or one DPDT (Dual Polarity Dual Toggle) Switch or using BJTs (Bi-Polar Junction Transistor). The easiest way is to use DPDT switch but if you wish to use microcontroller, then you will need to create a BJT H-Bridge circuit. Now make the connections as shown in the circuit diagram of the DPDT switch.
Make a truth table for all the possible inputs of the switches for your convenience. For the power supply you can use an adapter or an eliminator or make your own transformer. Select your power source with enough current rating so that the speed of motor does not decrease during an obstacle. The best way is to make your own power supply. To build your own power supply, purchase a transformer of 220V to 24V, 4A rating and apply a Bridge rectifier to it. Use 1N4007 diodes and 2200 microF capacitor for bridge rectifier.
By now your car must be complete. So enjoy with your car and test it on various tracks. Modify your car if required.
Originally published at http://www.zhagdoo.com on February 7, 2008.
