Transmitting Sound Pressure Level(dB)
-6 dB Directivity (deg)
Transmitter / Receive
Allowable Input Voltage(Vp-p)
Operating Temperature (℃)
Storage Temperature (℃)
Metals of case
The ultrasonic receiver includes the ultrasonic receiving probe, the signal amplifying circuit and the waveform transforming circuit. Ultrasonic probe must be used with the launch of the probe model, the key is the frequency to be consistent, the design uses CSB40R, otherwise it will not produce resonance and affect the receiving effect, or even unable to receive.
As the probe after the change of sine wave electrical signal is very weak, it must be amplified by the amplifier. Sine wave signal can not be directly received by the microcontroller, the waveform must be transformed. In accordance with the principles discussed above, the microcontroller needs only the first echo of the moment. Receiving circuit design can be dedicated receiver circuit can also be used to achieve a common circuit.
Ultrasonic propagation in the air, the energy attenuation is proportional to the distance, the closer the distance the stronger the signal, the farther away the signal weaker, usually between 1mV ~ 1V. Of course, there is a difference between the output signal strengths of different receiving probes.
Due to the large input signal range, the gain of the amplifier circuit puts forward two requirements: First, the amplification gain should be large to meet the needs of small signals; second, the amplification gain should be able to change to meet the needs of a wide range of signal changes .
In addition, since the input signal is a sine wave, the amplifier circuit must be designed as an AC amplifier circuit. In order to reduce the use of negative power supply, the amplifier circuit uses a single power supply, signal amplification and conversion using an LM324 general purpose operational amplifier, the first three for the amplifier design, the latter for the comparator design.
The LM324 can work both as a dual power supply and as a single power supply, thus meeting the usage requirements. To meet the needs of the exchange of signals, each level of the amplifier are used for resistance-level circuit level shift, that is, C7, C21, C22 and C24 in Figure 3, the capacity is 10μF, to achieve a single power supply AC signal amplification. For AC signals, the capacitor is short-circuited, so the gain of the first three stages of amplification is 10.
When the distance is relatively close, the amplifying gain of two stages has been able to output a signal of sufficient intensity, and the signal saturation of the third stage may occur. However, when the distance is far, three stages of amplification must be adopted. Reasonable adjustment potentiometer R27, select the reference voltage can make the measurement more accurate and stable.