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object position detection using ultrasonar

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the_edge

the_edge

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Hi, I have a little project. I have to measure distance between two points. And this is how.
I need to have one transmitter that will be the object and one receiver that will be static. Well I need to measure distance to that object. there is optic visibility, but I cannot use laser to do that because it doesn't have to be pointed to receiver. Any help, any idea how to do that will be appreciated. And the biggest problem is that it must be close range, between 3 and 20 meters.
 

Re: How to measure distance?

the_edge said:
Hi, I have a little project. I have to measure distance between two points. And this is how.
I need to have one transmitter that will be the object and one receiver that will be static. Well I need to measure distance to that object. there is optic visibility, but I cannot use laser to do that because it doesn't have to be pointed to receiver. Any help, any idea how to do that will be appreciated. And the biggest problem is that it must be close range, between 3 and 20 meters.
Click to expand...
ELECROMANETIC REFLECTION PRINCIPLE WE CAN USE
 

Re: How to measure distance?

dfullmer: ultrasonic is no good, as I said it doesn't have to be pointed to static point.





ELECROMANETIC REFLECTION PRINCIPLE
Click to expand...
Is there any book on this? Can you point me to basics?
 

Re: How to measure distance?

the_edge said:
dfullmer: ultrasonic is no good, as I said it doesn't have to be pointed to static point.





ELECROMANETIC REFLECTION PRINCIPLE
Click to expand...
Is there any book on this? Can you point me to basics?
Click to expand...
NO SPEACIFIC BOOK.YOU CAN READ RADAR BBOK SKOLNIK
 

    the_edge

    the_edge

    Points: 2
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Re: How to measure distance?

I think the most straigthforward solution is ultrasound
 

Re: How to measure distance?

my opinion: ultrasound.

send a short signal via speaker.
receive with a microphone.
calculate the time between signals tx-rx
sound speed propagation is 340m/s

\[
Distance = time (seconds) * 340 m/s\]
 

Re: How to measure distance?

send a short signal via speaker.
receive with a microphone.
Click to expand...

Problem with this is synchronization... I have to know exact moment of sending signal, that is not easy because they are not connected with wire. And signal can bounce of walls if I measure in the room, and I can get wrong readings. But thanks anyway...
 

Re: How to measure distance?

u may use very high frequency chips which will b used on transmitter and reciever separately

now a days multi channel chips and high frequency RF chips are easily available
so u can use

let u have to calculate the distance from static point i.e. u need readings to shown on static point

u will be using multi channel ic

let it is 8bit ic
make first 4 bits as a code and other 4 as data

CCCC-DDDD
CCCC=1010 means return the same DDDD to transmitter

now the transmitter is sending from 1end and receving the signal from other ic on other channel. use formula s=vt and calculate distance by measuring t and using RF speed as v

it is the best solution but it needs very very high frequency/speed ics due to small distance
 

Re: How to measure distance?

it is the best solution but it needs very very high frequency/speed ics due to small distance
Click to expand...

This was my biggest problem. 15meter distance is for about 1nS...
Can you tell me what IC could I use?



I thought of doing something different. I get an idea of useing RC circuit and this is how: I precharge the capacitor, and then send a signal, at that moment I start discharging the capacitor. Object gets the signal and sends it back. When I receive the signal, I stop discharging the capacitor and sample the voltage from it. Amplyfie it and then take it to A/D converter... By knowing all delays of circuits, and RC contsant I can determine the distance (theoreticaly)... Well this idea just came to my mind, so if anyone can direct me to possible problems...
 

Re: How to measure distance?

The simplest method is sonar. Reflections can be detected as the shortest path between Tx and Rx will always be the direct and thus first echo. The distances you are looking at are very short, any electromagnetic solution (light, radar) will be very complicate due to the high speed of transit. This would require complex interferometry techniques - hard to count that fast.
Don't have to worry about when the tx pulse happens - send two pulses with a known time in between. From this time, you can determine the distance the two rx pulses take. Choose your time interval carefully so as not to get too much interference from reflections. Should also use different frequencies.

Swingbyte
 

    the_edge

    the_edge

    Points: 2
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Re: How to measure distance?

You can use audio signals which travels at a very slowers speeds. you just need a speaker and a mic. By synchronising the transmitter and receiver you can measure the distance.
 

Re: How to measure distance?

Here are some approaches:
1) ultrasonic,
which needs basic information about sound waves.

2) tdr(time domain reflectometry),
which is a measurement in time domain and calculating the discontinuities in the line or in the circuit.
This needs information on the time and frequency domain.
This is really accurate for microwave measurements.

I hope they help.
 

Re: How to measure distance?

TDR is based upon impedance mismatch.
If you are interested in that field, I can send you some files.
tell me, I'll be happy to help to.
 

Re: How to measure distance?

Yes but I need to measure distance from separate point, not in the cable...
 

How to measure distance?

ultrasonic is easy and best you can use a microcontroller like 8052 to generate ultrasonic wave through its timer and u can use another timer to detect the reflected wave duration then calculate the distance using the standard equations there are some project's available on net using PIC microscontroller
 

Re: How to measure distance?

There are ultrasonic distance measuring devices sold at Sears and most hardware stores which should have the range to do the job. Most of these are based on the work of Polariod who developed the technique for use on their cameras to allow automatic focusing. These devices use a series of pulses at about 50 kHz and are capable of fractional inch accuracy.
 

Re: How to measure distance?

I would try to use ultrasonic to measure the distance and light for syncronization. Both of these can by transmitted in an omnidirectional pattern. You will need to know air temperature for accurate distance measurement using ultrasonic though.
 

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