Infrared remote control light switch circuit (2)

This example introduces an infrared remote control light switch, which also consists of two parts: an external light transmitter and an infrared light receiver
. The infrared light transmitter circuit is shown in Figure 212 (a). In the figure, NAND gates III and Iv form a multivibrator with an oscillation
frequency of 20kHz. When the power switch S is turned on and the transmit button SB is pressed, the two input terminals of NAND gate 1
become high level and the output terminal jumps to low level, so NAND gate II outputs high level. This high level is added to
the first input terminal of the NAND gate I1, which is the 9th pin, so the multivibrator starts to oscillate. The oscillation signal is output from the 10th pin. After being
amplified by VT1, it drives the infrared light-emitting diode VI-1 outward. Transmit infrared remote control signal. When SH is released,
the output terminal of NAND gate II jumps to low level, which stops the oscillation and interrupts the infrared light emission. The function of (,, R. and c. in the figure
is to eliminate the jitter generated when the button SH is pressed or disconnected, which can avoid generating flood action signals.
    The circuit of the infrared receiver is shown in Figure 21 2(b), The three inverters of A2 in the enclosure form a high-gain amplifier.
When the infrared receiver VL.2 receives the remote control command from the transmitter, corresponding
electrical signals ', R, coupled with A2 for amplification. The amplified signal is added by C. to the
input terminal ③ pin of the audio decoder A:3 (I,M:Jli7) for frequency identification. If the input signal frequency is the same as the internal voltage-controlled oscillation of A3 When the center frequency of the transmitter is equal to I,
its output pin ⑧ jumps from high level to low level, relay K absorbs, contact kl closes, and light E
lights up. After releasing the transmitter button SB, although A3 Pin ⑧ returns to high level , but because the circuit K uses
a static and non-power-consuming memory self-locking relay (DC5V ZS Ol type), with the help of the special
mechanical structure inside the relay, the trigger k 1 can still keep closing. urgent, so the light E can continue to shine. When you need to turn off the light, just
press --r SB of the transmitter again, the relay fork is energized once, it is triggered by an electrical pulse, the state will
flip , the contact kl will trip, and the light E goes out.
    The external resistors RP and (1) connected to the ⑤ and ⑥ pins of A3 determine the center frequency of the internal voltage-controlled oscillator. Adjust
the RP resistance so that the center frequency is the same as the transmitter's transmission frequency, and the receiver can be reliable. T, so this electronic shoe
will not be interfered by other infrared light. The value of capacitor C determines the frequency capture bandwidth of the internal phase-locked loop of A3,
which can be adjusted according to actual needs.