Remote control anti-theft alarm circuit controlled by PIC microcontroller

The circuit of the AG9900 intelligent remote control motorcycle anti-theft system is shown in Figure 1 and Figure 2. The single-chip microcomputer PIC16C54 is the main controller, and VD5026 and VD5027 are codec circuits. The alarm has functions such as sound and light three-level chain anti-theft, flash rolling alarm, anti-robbery, keyless driving, overtaking and car search, release of flameout and sensitivity adjustment. Its full remote control operation is very suitable for installation and use on motor vehicles. 1. Transmitting circuit VD5026, T4, etc. in Figure 1 constitute the remote control transmitting unit. One channel of the 12V power supply directly supplies the high-frequency transmitting circuit, and the other channel, when the transmit keys K1~K4 are pressed, is divided by D10 and R24~R27 to obtain a voltage of about 5V, which is supplied to the VD5026 through D6~D9. When one of the transmit keys K1~K2 is pressed, the pin will output a coded pulse train, which will be transmitted after high-frequency modulation by T4 (the frequency of the high-frequency oscillator composed of T4 is about 180MHz). A0~A7 of VD5026 are the encryption address encoding input terminals. Each bit has three states: "1", "0" and open circuit. A8~A11 (D0~D3) have dual input functions. They can be used together with A0~A7 as address coding input terminals or as control data coding input terminals. They are connected to "0" or "1" respectively (not marked in Figure 1 out). Pin TE is the starting end for encoding pulse transmission, and is active at low level. When the encoding pulse of the sending pin of VD5026 is low level, it outputs the serial pulse of encrypted address and data encoding. , the pin is connected across the oscillation resistor R28, its frequency f0=1.6×106/RHz, which is about 900Hz. 2. Receiving, decoding, instruction processing and interface circuit Figure 2 is the receiving, decoding and output circuit. When antenna Y receives a high-frequency signal, it is input to the common-emitter-common-base cascade high amplifier composed of T1 and T2 through high-pass filtering by C1, L1, and C3, and then input to the emitter of T3 by C4. T3 and the external LC network form a super-regenerative detection circuit, which detects the 900Hz encoded pulse train, and sends it to the decoder VD5027 pin (encoded pulse input end) after two-stage amplification by IC4. When used, the encryption address encoding of VD5027 is required to be consistent with the encoding of VD5026. Its ~ pins (D0 ~ D3) are control data output terminals, and each bit has only two states: "1" or "0". The pin is the decoding output terminal. When decoding is valid, VT changes from low level to high level. This pin together with the ~ pin provides the basis for status judgment of the microcontroller. The microcontroller receives the decoded signal and puts the system in the corresponding working state. Its,,,~ pins respectively control anti-theft settings, remote start, release of flameout, sound alarm, blinking of direction lights, etc. When the microcontroller is in the above alarm state, the corresponding pin level changes from low to high, and then the corresponding relay is driven by IC3. The detection element of this machine is played by BZ piezoelectric buzzer. When there is a theft, the signal detected by BZ is amplified by two levels of IC5 and sent to the microcontroller, and the microcontroller makes corresponding judgments and outputs accordingly. The 2P plug of this machine supplies power to the electronic horn of the alarm. The sensitivity of this machine is adjusted by controlling the level of the BZ vibration signal output to IC2 pin (there are 10 levels in total, not shown in the picture). Due to space limitations, other functions of this machine will not be described in detail here.