ultrasoniciinfra-red barrier

ultrasonic/infrared barrier elektor november 1983 Infrared barriers are used in counters, alarm equipment, automatic door- openers, remote control, and in countless other applications. It is therefore not surprising that almost every electronics hobbyist has at one time or another experimented with infrared diodes. Piezo-ceramic ultrasonic oscillators have been around even longer and yet nobody seems to have bothered to design an ultrasonic barrier with characteristics which compare well with those of its infrared counterpart. So far, that is! We have, and we feel it"s worth passing on to you. ultrasonic/infrared barrier Figure 1. The transmitter consists basically of two square-wave generators which operate as a fre- quency modulator. The modulated signal is amplified in a power stage before being applied to the barrier. Figure 2. The receiver essentially comprises two tone-decoders of which one operates as discrimi- nator and the other as signal-decoder. The relay in the output ...