Ultrasonic remote control light switch circuit

Ultrasound has the advantages of being indispensable and not causing interference with household appliances, so it is very
popular among people in situations where there is a problem. I would like to introduce to readers a real-life ultrasonic remote press! Light switch, which
consists of an ultrasonic remote control transmitter and a receiver.
    The ultrasonic remote control transmitter circuit is shown in Figure 223 (a). NF, 555 time base circuit Al constitutes
a white-excited multivibrator with a frequency of about iOkHz. The }n signal is output from the ③ pin and amplified by VT1 and VT2 to drive the ultrasonic transducer 1{ 】
radiate ultrasonic remote control commands into the air. RPl is a fine-tuning resistor. Adjusting it can fine-tune the oscillation frequency so that it can operate correctly
at 40kHz.
    The ultrasonic remote control receiver IU path is shown in Figure 223(b). It consists of ultrasonic receiver energizer B2, preamplifier
VT3, voice control ASIC A?, electronic control and power circuit and other parts.
    Assume that when the output terminal of A2, i.e., pin ⑥, outputs low level, VTd is cut off, relay K does not operate, its moving
and closing contact k-1 is open, and the light E lights up. If you press the button SB of the transmitter at this time, H2 will convert the received
ultrasonic signal into the corresponding electrical signal, which is pre-amplified by VT3, and then sent from G to the input terminal of A2,
that is, pin ①, so that A2 internal trigger The device flips. Pin @ outputs high level, VT4 is turned on, relay K is
closed, contact kl is closed, and lamp E is powered on and emits light. If you press the SB of the transmitter again. After the receiver receives the signal
, the @ pin of A? will turn back to low level, VT4 will be cut off, and the light E will go out. R. with R. forms a voltage divider,
and R. The resistance value is slightly larger than
Ra, so the static DC level of
the input pin ① of A2 is slightly higher than I/2V. , which can make the voice control integrated circuit A2 in the highest receiving sensitivity state.   ^1 can use ordinary time base circuits such as NE555, and A2 uses SK_T type voice control circuit. Yin and Bianstone adopt T (: T40-12F2 and TCT40 12s2 type piezoelectric ceramic ultrasonic transducers produced by Henan Province = Sanjia Xijinjubao Electronic Manufacturing Room (http:/, + www.jinjuF)ao com). ( H, T40-12F2 is the transmitting transducer. TC140-12S2 is the receiving transducer), its effective operating frequency is 40 ± 1 kHz. The transmitting head and the receiving head should not be confused during use, otherwise they will not work properly. T is a 220V/12V, 5VA small high-quality power transformer. K uses JZC-22F and T1r1, and V is a small power transformer. There are no special requirements for components.