Automatic reverse braking and distance measurement using ultrasonic

This Braking system is consists of ultrasonic sensor, Control Unit, Pneumatic breaking system. The Ultrasonic sensor is used to detect the obstacle. There is any obstacle in the path, the ultrasonic sensor senses the obstacle and giving the control signal to the breaking system. The pneumatic breaking system is used to break the system.
‘ULTRASONIC DISTANCE METER” is suitable for measuring distances between 25 cm and about 6 m. The measured distance is shown on a 3-digit liquid crystal display (LCD).
The transmitter element emits bursts of 12 pulses at a frequency of about 40 kHz. This frequency is roughly identical with the resonance frequency of the two transducers, so that some sort of selectivity is obtained at the sensing element. As soon as the first burst is emitted, a bistable is activated which enables the counter. Immediately after the burst has been emitted, the unit is switched to reception.
The sensitivity of the receiver is a function of time. During and immediately after emission of the burst, the sensitivity is low. The crosstalk between the transduction and sensing elements has, therefore, no effect on the operation on the unit. If an echo is received very soon after cessation of the emitted burst, it will be sufficiently strong to be processed by the receiver in spite of the very low sensitivity. An each that takes a longer time to reach the sensing element will be weaker, but by then the sensitivity of the receiver has become higher. The upshot of this arrangement is that reliable measurements, unaffected by spurious reflections and crosstalk, may be made with relatively simple means. At the instant the echo is sensed, the bistable is reset and the counter state transferred to the output latch.
Since the clock frequency is 17.05 kHz and the velocity of sound under normal atmospheric conditions may be taken as 341 m/s, the period of the clock is equal to the time taken by the burst to travel 2 cm, i.e., 1 cm forward and 1 cm back. This means that the number of clock pulses counted between the onset of emission of the burst and the sensing of the echo is equal to the number of centimeters between the transducers and the reflecting surface.

  1. Distance measurement upto 6 meter
  2. Fast pick-up
  3. Low maintenance expenditure
  4. Good efficiency
  5. LCD is used to measure the distance in meter..
  6. Microcontroller IC 89C51 has large memory capacities.
  7. Simple, easy to construct.
  8. Battery low indication is provided in the LCD display for weak battery replacement


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