DC Motors are commonly used in electronics and electrical projects. It may be a line-following robot, a remote-controlled car, electronic shutters and doors, digital locks, drones and choppers etc, the DC motors are used in a variety of applications. A lot of these applications require remote controlling the operations of the DC motor. Here, controlling the motor refers to switching motor on or off, changing its speed and altering the direction of its rotation. For example, a remote controlled car may require starting moving or halt, increase or decrease acceleration or move forward or backward by controlling the above mentioned factors of the DC motors attached to its wheels.
This project is a simple demonstration of remote controlling a DC motor by switching it on or off and changing the direction of its rotation. The concept illustrated in the project can be used in a number of applications where microcontroller may or may not be in use. Any other complex project using microcontroller can utilize this concept by altering the receiver section of this project where the DC motor circuit interfaced directly to the RF receiver here can be interfaced through a microcontroller too.
The RF Module used in the project is 434 MHz module. It transmits data at a baud rate of 1Kbps to 10 Kbps and can have an operational range of up to 300 metre. Learn about the basic setup of RF transmitter and receiver. The operational range can be extended by using an antenna of standard size and increasing the transmission power of the antenna. Learn more about increasing operational range of RF module.
The RF module can transmit 4-bit data at once. A set of 2 bits is required as control signal for remote operating a single DC Motor. The project shows controlling two 12V 3000RPM DC motors at the receiver section using the 4-bit control signal. The L293D IC (which can control maximum two DC motors) is used in the circuit.
|Sr No.||Name of teh component||Required|
|1||RF TX Module (434 Mhz)||1|
|2||RF RX module(434 Mhz)||1|
|6||Resistor – 1KΩ (Quarter watt)||8|
|7||Resistor – 1MΩ (Quarter watt)||1|
|8||Resistor – 50KΩ (Quarter watt)||1|
|11||BatterY - 9V||1|
|12||Battery - 12V||1|
|16||8x1 DIP Switches||2|
|17||Resistor network 8x1@1K||2|
The circuit has two sections - transmitter and receiver. The transmitter section is the basic setup of RF transmitter by connecting RF transmitter to an antenna and HT12E encoder IC. The address byte of the transmitter is set to be 0x00 by grounding all the address pins and pin 14 is also hard-wired to ground to enable an uninterrupted transmission. The push-to-on switches are connected to the data pins of encoder IC which are connected to VCC at other terminal. By default the encoder's data pins are connected to ground but on pressing a switch, the respective pin gets a HIGH input.
At the receiver side, RF receiver is configured according to its basic setup as dictated by the datasheets of RF receiver and HT12D decoder IC. The address byte of decoder IC is set to 0x00 to match with the address byte of RF transmitter.
The data bits D0 to D3 of the HT12D decoder IC are connected to L293D motor driver controller. The data bits cannot be directly interfaced to L293D IC. The DC motors run on high current 12V DC supply whereas the RF receiver circuit operates on 5V supply. A back current from the DC motor circuit can damage the data pins of the decoder IC. Therefore, the data pins are first connected to opto-couplers which stop the back current. The opto-coupler is a sort of optical isolator or an optical relay. The opto-coupler has an in-built IR diode at one end and a phototransistor at the other end. When current flows through the IR diode, it triggers a current in the phototransistor according to its configuration. The 4N35 opto-couplers used in the circuit has 6 pins with following pin configuration - :
|1||IR diode's anode||Anode|
|2||IR diode's Cathode||Cathode|
The data pins of the decoder IC are connected to anode pin of the opto-couplers and cathode pin of the opto-couplers is grounded. The collector of opto-couplers is given VCC and output current for the L293D IC pins is drawn from the emitter pin of opto-couplers. One opto-coupler is used for each data pin of the decoder IC. The respective data pin statuses are reflected as it is from the emitter pins of opto-couplers.
The L293D is the motor control driver IC. It has 16 pins with following pin configuration :
|1||Enable pin of input 1 and 2 of Motor 1||Enable 1,2|
|2||Input 1 for Motor 1||Input 1|
|3||Output 1 for Motor 1||Output 1|
|6||Output 2 for Motor 1||Output 2|
|7||Input 2 for Motor 1||Input 2|
|8||Supply voltage for Motor 1 and 2||VS|
|9||Enable Pin of input 1 and 2 of motor 2||Enable 3,4|
|10||Input 1 for Motor 2||Input 3|
|11||Output 1 for Motor 2||Output 3|
|14||Output 2 for Motor 2||Output 4|
|15||Input 2 for Motor 2||Input 4|
|16||Logic Supply Voltage||VSS|
The collector pin of opto-couplers interfaced to D0 and D1 are connected to Input 1 and Input 2 of the L293D IC respectively. The motor to be controlled by D0 and D1 bits is connected between Output 1 and Output 2 pins of L293D. The collector pin of opto-couplers interfaced to D2 and D3 are connected to Input 3 and Input 4 of the L293D IC respectively. The motor to be controlled by D2 and D3 bits is connected between Output 3 and Output 4 pins of L293D. A 5V supply is given to VSS pin and 12V supply from another battery is given at VS pin of the IC. The pins 4, 5, 12 and 13 are connected to ground.