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Ultrasonic Ranging circuit schematic showing

2017-08-15 08:03  
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Next is the display of ultrasonic distance measurement circuit. Spend the first few seconds glance at the diagram, you will find that the cost of the circuit. It uses a  PIC12C508  to perform control functions and standard 40 khz piezoelectric sensors. Drove to the transmitting transducer may be a simple image directly driven. 5 v drive can give a useful range for large objects, but may have problems detecting small objects. The sensor can handle 20 v the car, so I decided to get up close to this level. A MAX232 IC, usually used to make and ideal for RS232 communication drivers provide 16 v drive. The receiver is a classic op amp circuit tw1o phase. Enter some residual DC block capacitor C8 always seems gifts. Each gain stage is set to 24 pairs of the total growth in 576 years. It is off 25 maximum gain can use LM1458. Gain-bandwidth product of LM1458 is 1 mhz. The maximum gain is at 40 khz 1000000/40000 = 25. The output amplifier is fed to a comparator LM311. A small amount of positive feedback provides a clean return to stabilize the output. Watching an echo on the oscilloscope shows that it is greater than the level at the close cross-coupled signals. I therefore adjust the detection threshold during this time, so only the echo is detected. 100 n charging capacitor C10 at approximately 6 v shattered. This discharge quickly through the 10 k resistor R6 to restore the sensitivity of the more distant echo. A convenient negative voltage operational amplifiers and comparators MAX232 generated. So I turned it off while listening echo. 10 uf capacitor C9 holds the negative rail on long enough to do it. In operation, the processor waits for an active low trigger pulse to come. Then generate only 8 cycles of 40 khz. Echo line is raised to signal the host processor starts. Improve the echo line is also closed MAX232. After a period of time, usually no more than 10-12mS will detect the echo of the low echo lines and images. The pulse width represents the flight time of sound waves break. If not then it will automatically detect the echo time about 30 ms (WDT tw1o times of the picture). Because MAX232 Close echo detection, you must wait at least 10 ms betw1een measurement cycle is / - 10 v charging. It reliably measured 3 cm, and will continue to detect and 1 cm, or less but the pulse width is smaller and did not get any. The average current consumption is reasonable in less than 50 ma and usually about 30 ma.

srf1 Ultrasonic range finder circuit