Multi-channel patrol detection control circuit a

(1) Circuit composition The multi-channel patrol inspection controller mainly consists of a temperature frequency conversion circuit (see Figure 6-30a), inspection program control, alarm,
decoding display circuit (see Figure), and power supply circuit (see Figure 6-30c) composed of other parts.
    (2) In detection control schematic diagram a, a germanium transistor is used as a temperature sensor. When the temperature changes, the resistance between the emitter plate and
the collector also changes, causing the oscillation frequency generated by the 555 time base circuit to change. According to the temperature change of the germanium transistor,
temperature frequency conversion is realized. Since the output signal power of the 555 time base circuit is relatively large (200mA, 12V), the output frequency signal does not need to be amplified and
can directly drive the subsequent circuit. 10 such temperature-frequency conversion circuits need to be made and placed in the equipment that needs to alarm.
    In Figure 6-30b, t consists of F1~F3 (CC4069) approximately (). The 2Hz trigger pulse circuit sends a pulse to the CP terminal of IC
I every 5 seconds, causing IC1 to cycle count, that is, the output terminal appears high level in sequence, causing the Sl ~ SlO (CC4066) analog switches to turn on in sequence, causing the temperature and frequency to change.
The frequency signal from the conversion circuit is sent to the input end of the coupling capacitor G in turn.
    The frequency decoding circuit composed of IC2 567 decoding circuit and peripheral components detects the frequency signals sent in sequence. When the temperature of a certain circuit
exceeds the limit range, its frequency will reach the set value. After 1C2 decoding, this frequency signal is decoded, so that pin ⑧ of IC2 outputs a low level, causing
the transistor VT to conduct, and the relay K to close. When the contact is closed, it can drive the buzzer to sound an alarm.
    When IC1 counts in sequence, the input terminal of IC 3 CH208 also shows a high level in sequence. After being coded by CH208, the corresponding field signal is output to drive
the common cathode digital tube display to achieve synchronization with the alarm circuit.
    The power supply circuit shown in Figure 6-30c adopts a two-level voltage stabilization method. The 7815 outputs a 15V voltage and is sent to the on-site temperature-frequency
conversion circuit through a long-distance wire . The 7809 outputs a 9V voltage for inspection and alarm circuit use.