SRF04 Sonic Module for Distance Measurement

The project is a combination of an ATmega128 microcontroller and two SFR04 sonic modules with a controller unit MAM128 to produce a distance measuring device.

The principle of measuring the distance is very simple wherein the time is measured between sonic transmission and echo reception and then dividing it by sound speed in this environment. An LCD screen is used to display the calculated distance. The distance measured by the sonic meter can reach from 3cm up to 3m and can reflect from 3cm obstacles at 2m distance. The AVR-GCC cross compiler is used to write the ANSI-C software for the source codes.

The ultrasound module consists of transmitter, receiver, control, and logic analyzer as it works with TTL level. The measurement starts with a defined trigger signal and the result is distributed over the echo line. The signal length of the echo line reflects the distance of the object in the recording area. The SRF04 timing requires 5V at 30mA with 40kHz frequency at a maximum range of 3m.

The sound wave used by the sonic module goes in all directions and the sound energy spreads out proportionally to area’s radius.

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