A Sensitive DIY Ultrasonic Range Sensor

Some ultrasonic range finders for my project. But most of the commercial sensors like Parallax`s PING sensor and other similar products are quite expensive, especially if multiple units are needed. So I thought why not building it myself The theory behind ultrasonic ranging is quite simple. Typically a short ultrasonic burst is transmitted from the transmitter.
A Sensitive DIY Ultrasonic Range Sensor - schematic

When there is an object in the path of the ultrasonic pulse, some portion of the transmitted ultrasonic wave is reflected and the ultrasonic receiver can detect such echo. By measuring the elapsed time between the sending and the receiving of the signal along with the knowledge of the speed of sound in the medium, the distance between the receiver and the object can be calculated. The picture below (source: Wikipedia ) illustrates this basic principal: In my design, I used separate transducers for transmitter and receiver. It is possible to multiplex the transmission and receiving with a single transducer (e. g. Maxbotix range finders ), but the design would be significantly more complex. There are quite a few ultrasonic transducers to choose from, and the main criteria are the resonant frequency, radiation pattern and sensitivity. Generally speaking, these parameters affect the measurement in the following ways: a higher resonant frequency can provide finer details of the surroundings due to the shorter wavelength. A more directional radiation pattern can also enhance the resolution of the measurement. Sensitivity affects the efficiency of the transducer and also attributes to the SNR (signal to noise ratio). I bought these 24 kHz transducers on sale (see picture below). These transducers are very inexpensive (around a dollar each, and even cheaper when on sale) but effective. With properly designed circuits these sensors...

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