Photoelectric control lullaby circuit

Because of the high pace of people's lives. Due to intense and fierce competition, many people suffer from insomnia, which poses a threat to their work and health. For this reason, this
section introduces a feasible and effective method. A piece of photoelectrically controlled hypnotic music can relieve you from the trouble of insomnia. Let you enter dreamland.
    (1) Circuit principle analysis The circuit is shown in Figure g-44,
using a 4N25 optical coupler. The output end has no feedback effect on the input end
, and the signal can only be transmitted in one direction to achieve light transmission
control. Optocouplers consist of light-emitting diodes and phototransistors
. Rj and 4N25 form a signal control circuit and control
VT1, VT2, K and Y to form an audio oscillation circuit. When the circuit
is normal, the DC output is added to the ① and ② terminals of 4N25 through the brother,
the light-emitting diodes light up, causing the ⑤ and ④ terminals to conduct, the VT1
base is zero-biased and cut off, and the audio oscillator does not work. When
the switch Sl at both ends a and b is short-circuited, the voltage is zero, the
light-emitting diode does not work, the phototransistor is turned off, and divides the voltage with Rz, and the base of VT1 provides a forward bias current to turn it on. The amplifier tube VT2 is working,
the relay K coil on the collector is energized, the K normally open contact is closed, the light-emitting diodes LED1 and LEDZ are sparkling, and the music circuit is working, playing a
beautiful and beautiful weekly famous song, taking you into dreamland. . Disconnect the SI circuit and return to the waiting state. The power supply uses dual 6V DC power supply.
    (2) Component selection: 4N25 optical coupler, KD-9300 for musical film, battery for +6V power supply, 1N4001 for VD,
JRX-13F low-power relay for K, VT1 force 3DG12. VT2 is 3CG21. I.EDl and LED2 use red light-emitting diodes with a diameter of +3mm
, and speaker BL uses small ones. Other component parameters are shown in Figure 9-45.
    (3) Installation and debugging: Design the printed circuit board according to the schematic diagram or purchase it yourself, weld the components on the printed circuit board, and install and fix the power supply
on the bottom plate of the chassis. The speakers are installed on the inner wall of the side panel of the chassis. The power switch, indicator light, and test jack are installed on the front panel. Just connect the wires according to the schematic diagram
. The minimum reference size of the chassis is 120×8mmz. Insulating materials such as wooden boards and plastic boards can be processed or purchased.