Single channel infrared remote control receiving circuit

It is an infrared receiving circuit . In the figure, [Cl is I. M567. LM567 is a phase-locked loop circuit, using an 8-pin dual-in-line plastic package.
The external resistors and capacitors connected to the ⑤ and ⑥ pins determine the center frequency of the internal voltage-controlled oscillator
^,^ a;l/l. 1RC. Its ① and ② pins are usually connected to ground through a capacitor respectively, forming
an output filter network and a loop single-stage low-pass filter network. The capacitor connected to pin ② determines
the capture bandwidth of the phase-locked loop: the larger the capacitor value, the narrower the loop bandwidth. The capacitance of the capacitor connected to pin ①
should be at least twice the capacitance of pin ②. ③Pin is the input terminal, and the input signal is required to be greater than or equal to
25rrN. Pin ⑧ is a logic output terminal, and inside it is an open-collector transistor,
allowing a maximum current of 100mA. The operating voltage of LM567 is 4.75-9V, the operating
frequency is from DC to 500kHz, and the quiescent operating current is about 8mA. The internal circuit and detailed working process of LM567
are very complex. Here, only its basic functions are summarized as follows: When
the @ pin of LM567 inputs a signal with an amplitude greater than or equal to 25mV and a frequency within its bandwidth, pin 8 changes from high level to low. Level, ② pin outputs
the frequency/voltage converted modulation signal; if the audio signal is input to the ② pin of the device, then the ⑤ pin outputs the
FM square wave signal modulated by the ② pin input modulation signal. In the circuit in Figure 18-57, we only use
the characteristic that the ⑧ pin voltage changes from high to low after receiving the carrier signal of the same frequency to realize the control of the controlled object.
    After analyzing the basic working principles and functions of LM567, it is very simple to analyze the circuit in Figure 18-60. Ic1 is an infrared receiver.
It receives the infrared signal from the transmitter. Its center frequency is the same as the carrier frequency of the transmitter. After demodulation by ia.,
it outputs , that is The same signal as point A in E 18-60b. We feed the center frequency of LM567 to
the same oscillation frequency as the "NAND" gates 1 and 2 in the transmitter, 4 is f2c,]. Then when the transmitter transmits a signal, the LM567 starts to work, and the @ pin
changes from high level to low level. This changing level can be used to control various objects. Using the circuit in the picture, we can make a remote
control switch to control various household appliances at home.