Remote Controlled Moon-walker

Moon walker is a six leg robot which can easily move on rough surface with the help of two DC motors. It can move in all four directions. For complete details about mechanism, assembly and drawing click here.

This moon walker project is to control the movement of moon walker through RF remote control which is built using HT12E and HT12D chips. The remote control is built using RF encoder chip HT12E that will generate different codes. These codes will be transmitted by 434 MHz RF transmitter. At the receiving side these codes will be received by 434 MHz RF receiver and decoded by RF decoder chip HT12D. These codes are fed to 89C51 to take a controlling action on moon walker.

The micro-controller will move the moon walker in all four directions as well as changes its speed also. Also one can program it to move some specific calibrated distance.

Note:- complete project is developed by four students Gajera Vijay, Patel Pradip, Vaghasiya Kalpesh and chikhaliya Anil of 4th EC from Dr. J. N. Mehta Govt. Polytechnic college, Amreli under my guidance.

Here are some of the images of moon walker

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There are two parts of project (1) remote control transmitter (2)moon walker receiver circuit

Remote control transmitter:-

The Circuit Diagram Tab 1 shows 4 channel remote control circuit for moon walker.

Its a single chip circuit built around HT12E. There are two main components HT12E and 434 MHz RF transmitter.

Connections:- All the address bits A0-A7 (pin no.- 1 t0 8) are connected to ground to set the address 00. A 1.1 M resistor is connected between oscillator pins 16 & 17. The data pins D0-D3 (pins 10 to 14) are connected with one of the terminals of switch through diode. The another terminal of switch is grounded. The Transmission enable pin TE (pin no. 15) is connected with all the data pins through four diodes. The Dout pin is connected to Din pin of 434 MHz RF transmitter. 9 VDC battery is used to power up the circuit.

Operation:- to understand the operation first read it would be better to go through the data-sheet of HT12D.

Whenever you press any key TE pin will be grounded through that diode, at the same time particular data line is also grounded. For example if you press S1 the data pin D3 will be grounded through diode D1 and at the same time TE will be grounded through D8.
So the address will be 00000000 and data will be 0111
So we can set the data at the same time we can pull the TE pin low by pressing single key
Now we know when TE pin is low the address and data are transmitted serially through Dout pin.
So 8-bit address and 4-bit of data are together transmitted over 433.92MHz carrier frequency.
When you press S5 or S6 two data pins together along with TE pin is grounded at a time so the data will be 1100 or 0011 with same address 00000000.
Thus by pressing four different keys we can generate and transmit four different codes for 4 different functions given in the table.

Switch	Code	Function
S1	0111	move moon walker forward
S2	1011	move moon walker backward
S3	1101	turn moon walker left
S4	1110	turn moon walker right

Moon walker receiver circuit

Moon walker receiver circuit:-

Circuit Diagram Tab2 shows schematic arrangement for moon walker circuit. We have to move two DC motors to move moon walker in all four directions. If both motors run clockwise then moon walker will move forward. If both moves anticlockwise then moon walker will move backward. When only one of the motor rotates and other stays, still moon walker will turn either left or right. To vary the speed PWM wave is generated by 89C51 and fed to H-Bridge driver so the average voltage is given to both motors so their RPM will increases or decreases.

Main components of the circuit are HT12D, 434 MHz RF receiver, Hex inverters 74LS04 and 89c51.

Connections:- The Dout pin of RF receiver is connected with Din pin (15) of HT12D. All the address lines A0-A7 (1-8) are connected to ground to setup same address both the side. The data pins D0-D3 (10-14) are connected with port P1 pins from P1.0 to P1.3. LEDs LED1-LED4 are also connected for indication. LED5 indicates valid transmission. The VT pin (17) of HT12D is connected to INT1 (13) pin of 89C51 through NOT gate. All the pins of port P2 are utilized to drive two DC motors through hex inverters and relay driver board. Two different regulated 5 V supplies are given to whole circuit through two 9 V Dc batteries.

Operation:- to understand the operation better first go through the data-sheet of HT12D

RF receiver will receive the code transmitted by transmitter demodulates it and gives to HT12D
When HT12D receives the code it will first checks and compares the address three times and when it finds perfect match it will give high output on VT pin indicated by LED5 and same time latches the same data transmitted by HT12D. That is indicated by LED1-LED4.
The VT pin also gives an interrupt to 89C51 through not gate.
When 89C51 is interrupted it will receive the code on port 1 and start comparing it with inbuilt codes.
When it finds match it will jump to that subroutine and perform that task.
Because the same code is received, a particular code will call one particular subroutine like the code 0111 will call subroutine forward and like wise.

Here I have provided a joystick control for the motion of moon walker means as you press the switch from transmitter to move forward (or any else) the moon walker will move forward for some time (predetermined) and then stops. So if you press and hold that key then moon walker will continue its motion.