Check the listing for details. 10PCS Ultrasonic ranging module sensor HC-SR04 support /51/STM32. Condition: New. Listed at 16.26 USD. Main technical parameters: 1: Use voltage: DC5V 2: static current: less than 2mA 3: Level output: high 5V 4: level output: bottom 0V 5: Sensing Angle: no more than 15 degrees 6: detection distance: 2cm-510cm 7: High precision: up to 0.3cm On-board wiring modes: VCC, trig (control end), echo (receiving end), out (empty pin), GND Note: TRIP pin is the internal pull up 10K resistance, use the MCU IO port pull down TRIP pin, and then give a pulse signal of more than 10us. The OUT foot is the switching output foot when this module is used as the anti-theft module, and the ranging module does not use this foot! Note: The module should be plugged into the circuit board and then powered on to avoid high level misaction. If it is generated, it can be solved by re-energizing. This module can provide measuring program: C51, PIC18F877, Yilong microcontroller, three kinds of MCU test reference. 3, URF04 module working principle: (1) Use IO trigger ranging to give at least 10us high level signal; (2) The module automatically sends 8 40khz square waves to automatically detect whether there is a signal return; (3) A signal is returned, and a high level is output through IO, and the duration of the high level is the time of the ultrasonic wave from transmission to return. Test distance =(high level time * speed of sound (340M/S))/2; The use of this product is simple, a control port sends a high level of more than 10US, you can wait for high level output at the receiving port. As soon as there is an output, you can open the timer, when the port becomes low power, you can read the value of the timer, at this time for the distance time, you can calculate the distance. This continuous periodic measurement can reach the value of your moving measurement ~~ Module working principle: (1) Use IO trigger ranging to give at least 10us high level signal; (2) The module automatically sends 8 40khz square waves to automatically detect whether there is a signal return; (3) There is a signal return, through the IO output a high level, the duration of the high level is The time of the ultrasonic wave from transmission to return. Test distance =(high level time * speed of sound (340M/S))/2; This module can provide a full range of ranging programs: C51, PIC18F877, ultrasonic LCD1602 display, ultrasonic LCD12864 display, digital tube display, serial port display, etc., ranging reference program.