Abstract
The article is devoted to the complete design of an intelligent barrier that uses piezoelectric ceramic transducers as transmitter of an acoustic signal and as a receiver. There is a relatively rich device base on the market for these transducers. These transducers are also not economically demanding. The barrier is composed of three identical bars. A continues wave rectangular signal generation is used for excitation of the converters on the transmitting side. The receiving side is more complex. A signal from the receiving transducer is first analog pre-processed and converted to logical values of 0 or 1. Subsequently, these signals are processed in a microcontroller system, evaluated and a possible alarm of a presence of an intruder is signaled using a display, a light-emitting diode and a piezoelectric siren. The display also shows the number of alarms. Some intelligence is added to the system by classifying a potential intruder. The functionality of the system is verified in a detail and discussed.