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i don't want to calculate manually... i just need to stop the car when it reaches the object at 5cm. Is that it need any calculation for this ? I am now implemented the transmitter and receiver but can not used it to avoid collision. I need brief explanation pleas!!!
No, there's no need for the PIC to do the calculation if you want a fixed distance. Do the calculation on paper and then pre-load the timer. If the signal return happens before the timer expires then: object <= your distance.
i don't want to calculate manually... i just need to stop the car when it reaches the object at 5cm. Is that it need any calculation for this ? I am now implemented the transmitter and receiver but can not used it to avoid collision. I need brief explanation pleas!!!
no no no... when I say 'you', I mean you set up your electronics to do it. you couldn't time it with a stop watch if you wanted to.
Leonardo DaVinci tried to measure the speed of light, manually, and quite cleverly also. He had two towers a known distance apart. He started counting when the first guy opened his lantarn. The person in the second tower opened his lantarn when he saw the light from the first lantarn. He stopped timing when he saw the light from the second lantarn. His conclusion: The speed of light was too fast to measure by hand, too much human error entered the calculations.
In the 60s, our astronauts left 'porro-prisms' on the moon. These are special mirrors that bounce light back in the exact same direction it comes in from. Then we could bounce lasers off of them and measure the distance to the moon. In the 70's this was accuarate to a couple of hundred yards (meters), mainly because of the accuracy of our timebases, our clocks. In the 80's - 90's this was refined down to a couple of inches. No telling how accurately they can measure it now.
Point is, *you* can't measure it, your electronic device does. How accurately depends on the accuracy of your time base. I would say the easiest way to measure it is to trigger a s/s (single shot - 555 or 74xx123) when you transmit. Set the pulse width for '10 cm' of sound travel (pulse has to go out and come back). If you get a return before the s/s times out - STOP THE CAR - If not, you are farther away. If that's all you want to do, you don't need to 'decode' the time and display it, although, after going through all this work getting the signal, it'd be a shame not to )
i need to convert the voltage from ultrasonic sensor into digital data so that to detect the obstacle distance.. what type of ADC can be used here which is easy ?
1) The 741 won't work at audible frequencies, let alone ultrasonic.
2) it doesn't measure the timing of the return signal, just the intensity, so you'll get a different result, if the object is made of something absorbent than if it's made of a reflective material.
1) The 741 won't work at audible frequencies, let alone ultrasonic.
2) it doesn't measure the timing of the return signal, just the intensity, so you'll get a different result, if the object is made of something absorbent than if it's made of a reflective material.
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