Published:2011/4/21 3:43:00 Author:TaoXi | Keyword: Car Search, Car Search Device, 555 Car Search Device | From:SeekIC
As shown, car search device composed of two parts, the transmitter and receiver. The transmitter is a medium wave frequency oscillaor with 555 as the core, the oscillator frequency should be selected lower than 535KHz, The value of frequency is decided by R1, RP1, C1 (F=1.44/(RP1+2R1)C1, L1, C2 form the output resonant circuit), then launch out by the antenna. Receiving circuit is composed of the input frequency selection network and the 741 op amplifier, magnification of the amplifier is decided by the ratio of RP2/R2. The LED1 ~ LED5 can be used to indicate the strength of the received signal, with the strengthening of the signal, LED will light one by one.
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