Ultrasonic distance ruler

Within a measuring distance of 1.3 meters, it is equipped with a lithium battery charging and discharging boost and protection circuit, and uses a red laser head to indicate the measuring direction.

Repeatable programming, program source code (MIT license) is given

About the source code: The measured values ​​are displayed directly without filtering. During actual application, it was found that the return pulse width of the ultrasonic module had a jitter of close to 30 microseconds (verified by a logic analyzer, not a microcontroller processing error), which is equivalent to a distance error of 5 mm, and the reason is unknown. Since the error is large and the display value is relatively stable except for this jitter, filtering has little improvement in performance, so the filtering function is not added to the program for the time being.

The laser head needs to be cleaned with a soldering iron and then installed into the PCB gap and soldered (note the polarity)

The ultrasonic module needs to be welded to the board, otherwise it will easily become unstable.