【文章內(nèi)容簡(jiǎn)介】 UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of 200ms. Ranging the right and the left side of the circuit, respectively, then input port and , the working principle and circuit in front of the same location. Reception and processing of ultrasonic Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the opamp amplification IC1A and after polarization IC1B to IC2. IC2 is locked loop with audio decoder chip LM567, internal voltagecontrolled oscillator center frequency of f0=1/, capacitor C4 determine their target bandwidth. R8conditioning in the launch of the high jump 8 feet into a lowlevel, as interrupt request signals to the singlechip processing. Ranging in front of singlechip termination circuit output port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port singlechip, while singlechip and received input IC3A, interrupted by the process to identify the source of inquiry to deal with, interrupt priority level for the first left right after. Part of the source code is as follows: Receivel: push psw push acc clr ex1。 related external interrupt 1 jnb , right。 pin to 0, ranging from right to interrupt service routine circuit jnb , left。 pin to 0, to the left ranging circuit interrupt service routine return: SETB EX1。 open external interrupt 1 pop acc pop psw reti right: … 。 right location entrance circuit interrupt service routine Ajmp Return left: … 。 left ranging entrance circuit interrupt service routine Ajmp Return The calculation of ultrasonic propagation time When you start firing at the same time start the singlechip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received time. When you receive the ultrasonic reflected wave, the receiver circuit output a negative jump in the end of INT0 or INT1 interrupt request generates a signal, singlechip microputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance. Some of its source code is as follows: RECEIVE0: PUSH PSW PUSH ACC CLR EX0。 related external interrupt 0 MOV R7, TH0。 read the time value MOV R6, TL0 CLR C MOV A, R6 SUBB A, 0BBH。 calculate the time difference MOV 31H, A。 storage results MOV A, R7 SUBB A, 3CH MOV 30H, A SETB EX0。 open external interrupt 0\ POP ACC POP PSW RETI For a flat target, a distance measurement consists of two phases: a coarse measurement and a fine measurement: Step 1: Transmission of one pulse train to produce a simple ultrasonic wave. Step 2: Changing the gain of both echo amplifiers according to equation, until the echo is detected. Step 3: Detection of the amplitudes and zerocrossing times of both echoes. Step 4: Setting the gains of both echo amplifiers to normalize the output at, say 3 volts. Setting the period of the next pulses according to the: period of echoes. Setting the time window according to the data of step 2. Step 5: Sending two pulse trains to produce an interfered wave. Testing the zerocrossing times and amplitudes of the echoes. If phase inversion occurs in the echo, determine to otherwise calculate to by interpolation using the amplitudes near the trough. Derive t sub m1 and t sub m2. Step 6: Calculation of the distance y using equation. The ultrasonic ranging system software design Software is divided into two parts, the main program and interrupt service routine. Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving control. Interrupt service routines from time to time to plete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of pletion time, distance calculation, the results of the output and so on. Conclusions Required measuring range of 30cm200cm objects inside the plane to do a number of measurements found that the maximum error is , and good reproducibility. Singlechip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error. Therefore, it can be used not only for mobile robot can be used in other detection system. Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency. Parking sensor Parking sensor introduction Reversing radar, full name is reversing the anticollision radar, also known as parking assist device, car parking or reversing the safety of assistive devices, ultrasonic sensors(monly known as probes), controls and displays (or buzzer)and other ponents. To inform the driver around the obstacle to the sound or a more intuitive display to lift the driver parking, reversing and start the vehicle around to visit the distress caused by, and to help the driver to remove the vision dead ends and blurred vision defects and improve driving safety. Reversing radar detection principle Reversing radar,