25-08-2017, 09:32 PM
ULTRASONIC COLLISION AVOIDING SYSTEM
The unique ultrasonic collision avoiding system makes use of the invisible, inaudible ultrasonic sound beam to detect obstacles at the distance of 1-2 mts. Ultrasonic transducers operate at max. efficiency when driven at 40kHz frequency. So an ultrasonic transmitter and the receiver pair operating at 40kHz is used to control the relay.
The transmitter unit is built around CMOS IC. By adjusting the 22-kilo-ohm preset (VR1), the oscillator frequency can be set to approximately transducer is driven by two complementary buffer stages of and its current drain is very low.
The receiver unit uses a two stage 40 kHz preamplifier followed by switching circuit, driver etc. adjust VR2 in the receiver circuit, the receiver senses ultrasonic sound from the transmitter. When the ultrasonic beam is reflected by the movement of a person or any other object path, npn transistor T4 stops conducting and transistor T5 conducts. It activates the buzzer and LED1 for three to four seconds. This duration depends on the time taken by capacitor (C8) connected at the base of transistor T5 to discharge fully through resistor R13. The duration can be set to a desired value with the values of C8 and R13.
The circuit comprising transmitter, receiver and associated circuits operate off a 9-12V regulated power supply. The receiver circuit requires regulated 12 v. You can also use unregulated power supply here.
PROJECT OVERVIEW :-
We present here is a SPY ROBO element robotic land rover that can be controlled remotely using primarily the RF mode. The RF remote control has the advantage of adequate range (up to 200 metres with proper antennae) besides being omnidirectional. On the other hand, an IR remote would function over a limited range of about 5 metres and the remote transmitter has to be oriented towards the receiver module quite precisely. However, the cost involved in using RF modules is much higher than of IR components and as such, we have included the replacement alternative of RF modules with their IR counterparts for using the IR remote control.
SPY ROBO can move in forward and reverse directions. You would also be able to steer it towards left right directions. While being turned to left and right directions . While being turned to left or right, the corresponding blinking LEDs would blink to indicate the direction of its turning. Similarly. During reverse movement, reversing LEDs would be lit. The decoder being used for the project has latched outputs and as such you do not have to keep the buttons on remote control pressed for more than a few milliseconds. This helps prolong the battery life for remote. The entire project is split into sections and each section is explained in sufficient detail.
FORWARD AND REVERSE MOVEMENT :-
To keep our design as simple as possible, we have coupled a 3-rpm geared 6v DC motor to the left front wheel and another identical motor to the right front wheel. Both these front motors are mounted side-by-side facing in opposite directions. Wheel rims ( 5cms diameter ) along with rubber wheels are directly coupled to each of the motor shafts. This arrangement does not require separate axles. During forward (or reverse) movement of the vehicle, the two wheel shafts, as viewed from the motor ends, would move in opposite directions (one clockwise and the other anticlockwise). For reversing the direction (forward and backward), you simply have to reverse the DC supply polarity of the two motors driving the respective wheels.
STEERING CONTROL :-
There are different methods available for steering a robotic vehicle. The commonly used ones are:-
Front wheels are used for steering, while rear wheels are used for driving. eg. in tractors.
Front wheels are used for steering as well as driving. It comes into play only when one rotate differentially with respect to each other.
All the four wheels are used for driving as well as steering.
Single front wheel is used for a driving as well as steering: e.g., in a tricycle.
Two driving wheels that are independently controlled to turn; e.g., in a tank.
DRIVE CIRCUIT FOR THE MOTORS:-
Here is a typical circuit for driving one of the motors, in forward or reverse direction, coupled to say, the left-hand front wheel. Simultaneously, the right hand motor has to rotate in the reverse direction for moving the wheel in the same direction. It means that input terminals of the motor drive circuit for the right hand motor have to be fed with reverse polarity control signals compared to those of the left hand motor drive circuit. In the H-bridge motor drive circuit when A1 input is made high and A2 is made low, transistor T1 (npn) is forward biased and driven into saturation, while transistor T2 (pnp), being reverse-biased, is cut-off. This extends the battery’s positive rail to terminal-1 of the motor. Simultaneously, transistor T3 is cut off, while T4 is forward biased and driven into saturation. This results in ground being extended to terminal-2 of the motor.
Now, of the two inputs are logically complemented, the motor will run in the opposite direction. When both the inputs are at the same logic level (Gnd or Vcc), the motor is at the rest. Thus we can control the movement (forward, reverse and stop) as well as the direction of rotation of the motor with the help of logic level of the two control input signals to the motor.
REMOTE CONTROL:-
For remote control, we have used Holtek encoder-decoder pair of HT12E and HT12D employing RF as well as IR principles. Both of these are 18-prin DIP Ics. Their pin configurations are in the test circuit.