Ultrasonic distance sensor module

July 04, 2018

Ultrasonic distance measuring module is a kind of product used to measure distance. It uses time difference and sound by sending and receiving ultrasonic waves.

The speed of propagation, the propagation speed of the ultrasonic wave in the air v , and according to the time difference between the measured emission and the received echo recorded by the timer Δt , the distance S from the obstacle to the obstacle can be calculated , that is : S=v · Δt / 2 thus calculates the distance from the module to the front obstacle.

Since ultrasound is also a kind of sound wave , its sound speed v is related to temperature . Table 1 lists the sound speeds at several different temperatures. In use , if the temperature does not change much , the speed of sound is considered to be substantially constant. Ultrasonic wave propagation speed is 334 meters / second at room temperature , but its propagation velocity V is susceptible to temperature, humidity, pressure and other factors in the air , which are greatly affected by temperature . For example , if the temperature rises by 1 °C , the speed of sound increases approximately. 0.6 m / s. If the accuracy of the distance measurement is very high , it should be corrected by means of temperature compensation (this system uses the temperature compensation method). When the ambient temperature T at the site is known , the formula for calculating the ultrasonic propagation velocity V is : V=331.45 + 0.607T .

There are many types of ultrasonic ranging module. At present, the URM37 ultrasonic sensor is more commonly used as the RS 232 interface, which can be adjusted to TTL interface . URM05 high-power ultrasonic sensor can measure distance up to 10 meters, which is currently far from the test distance. a, and in addition to the more commonly used foreign funds of a South Korean Hagisonic ultrasonic distance sensor module - HG-C40U.

Ultrasonic ranging sensor module - HG-C40U is a dimension of 50x22x25 (mm), the sensor module Φ16, the maximum measurable distance to the obstacle is 3.5m (at 5V), 5m (at 12V), resolution 5mm Within . The HG-C40U also has two input voltages: 5V and 12V . The factory default is set to 12V . Communications to send data mining UART communication in UART mode is triggered, if the starting command is generated by the UART, only send data, send: #Mode | 2 (becomes an external trigger mode), the receiver: Mode | 2 ->!! Data Set Complement . The signal output uses the ' Interface board ' (RS232, power regulator ) data to display the communication between the sensor and the PC . The monitor program ( Usable HyperTerminal ) on the PC and the high-performance ASIC chip are used to ensure stable transmission and sensitive reception.

Ultrasonic distance sensor HG-C40U connector configuration:

HG-C40U ultrasonic ranging sensor is disposed UART:

HG-C40U ultrasonic ranging sensor communication protocol:

The operating mode is used for ultrasonic modules and is divided into three types: free-running , UART- triggered and external-triggered modes . The free-running mode triggers ultrasonic waves at regular intervals . The UART trigger mode uses periodic or random UARTs for external ultrasonic triggering ( triggered commands ) . The external triggering mode requires external triggering signals for regular or irregular interval triggering signals. When in display working mode send : @mode , receive : ! mode -> @ Mode |0 . The operating mode setting (UART trigger ) is set to %. Transmit : #Mode|1 ( becomes UART trigger mode ) , %. Receive : !Mode|1 -> !Data Set Complement .