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Subject: Re: ultro sonics distance detector !

Date: 04/20/02 at 2:53 AM
Posted by: Jem
E-mail: Jemidar@hotmail.com
Message Posted:

In Reply to: Re: ultro sonics distance detector ! posted by naresh on 04/19/02 at 5:25 PM:

Check this site. That is probably the easiest way for you to begin. Their modules are not that expensive, and they have taken care of the three most difficult areas about ultrasonic ranging:
1. Driving the transducer. Some require quite high AC voltages riding on high DC voltages.

2. Time-dependent gain. The farther the target is, the fainter the echo becomes, and the higher must be the receiver gain then.

3. Echo suppression. This is required unless the system uses separate transmit and receive transducers (which may require careful aiming). Basically, immediately after switching from Tx to Rx, the transducer is still vibrating, and will detect this as a false return echo. The easiest suppression is just a small time delay to allow the transducer to receive the true echo. This limits the near range a bit though.

The site also provides a complete evaluation package for distance measurement using a small microcontroller. You may want to check it out, or build your own. All you need to do is to be able to measure a time delay (echo return time), and do some maths using the speed of sound, and you get the distance. A further improvement is to sense ambient temperature (or even pressure) to provide a correction factor for the speed of of the sound pulse.

Hope this helps....


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