Household appliances remote control circuit

The audio remote control
for household appliances uses the condition that the home phone is compatible with dual tone dialing or dual tone pulse. The audio remote control is attached to the user's phone line. When the owner is away from home, he only needs to dial the home phone to remotely control the home phone. The electrical appliances on the power supply can be switched on and off, making it
easy to use. After adding this remote control, it will not affect the normal receiving and making of calls.
    (1) Circuit working principle
    1) The circuit composition is shown in Figure 18144. In the figure, ca,. Optocoupler, VT3, VT4, etc. form a ring current detection circuit; IC4 (555)
forms a simple delay circuit; VT1, VT2, LED1, Rs, etc. form an analog off-hook circuit; Icl and IC2 form a dual audio signal reception,
Decoding circuit; D flip-flop and relay constitute the execution circuit.
    2) Working principle analysis: The dual audio signal on the telephone line first passes through the dial tone filter inside the dual audio signal receiver lCl to filter out the dial
noise signal, and then is pre-amplified and sent to the dual audio filter to convert the dual audio signal Separate according to high and low audio signals, and
send them to the output decoding circuit through high and low frequency filters and amplitude detectors respectively. After digital operation, the corresponding 8421
code is output at its data output terminal (~~@ pin). It should be pointed out that for the "o" number, the 8421 code output by IC1 is not "0000", but "1010". The 8421 codes output by IC1
are "1011" and "1100" respectively. If you connect the power of the 6th electrical appliance at home outside, you can make a call home. At this time, the exchange
will send a 90V, 25Hz ringing signal to the home phone. This ringing signal passes through C8 and RH and causes the circuit to The light-emitting tube in the optocoupler
lights up, and the power supply charges C through RP, R}a and the photosensitive transistor. Since the ring signal is intermittent, the charging process is also intermittent
. When there are 6 intermittent ring current signal inputs and the voltage across G reaches the peak voltage of VT4, VT4 is turned on, the voltage at both ends of Ru rises,
VD1 is turned on, and VT3 is turned on. At this time, pin ② of IC4 becomes low level, IC4 is set to a temporary stable state, its ③ pin outputs a high level,
VT2 is turned on via R7, VT1 is also turned on, LED1 is on, and the phone is in a simulated off-hook state. , the ringback tone in the caller's receiver
will disappear. At the same time, because the music piece 1C3 is triggered, a piece of music is output and sent to the caller's receiver through the telephone line and switch. After the caller
hears the music, he can press the number key "6", and the phone will send out a 770 The +1447Hz dual audio signal (the caller can
hear it from the receiver) is sent to the telephone line through the switch, and then sent to the input end of lcl via VT1, G, and MA. After internal processing, it is translated at its
output end. The corresponding 8421 code is output and the input terminal of a 4-16 line decoder JC2 is given. After this code is decoded, its ⑤ pin outputs a high level,
causing the D flip-flop composed of CD4013 to flip, the Q terminal outputs a high level, VT5 is turned on, K2 is closed, and the power supply of the 6th electrical appliance is turned on. In the same way,
pressing other keys can also remotely control the power of other electrical appliances. Gradually increase over time. The voltage at both ends of G gradually increases, when the voltage rises to
2/3 of the power supply voltage (about 15s). IC4 is reset, its ③ pin becomes low level again, VT2 and VT1 are cut off, LED1 goes out, and the entire remote control process
ends.
    In addition, this machine is also equipped with 12 manual key switches SA1~SA12. People can press these switches to control the on/off of 12 electrical appliances after returning home.