Use CD4013 to make a single-button touch light switch

The touch switch circuit made with CD4013 digital integrated circuit is shown in Figure 3-24. The right part of the dotted line of the Junior High School is the ordinary power supply
wiring, and the left part is the touch light switch circuit.
    The main circuit of the switch is composed of VD1 ~ VD4 and vs, and the integrated block A and other components form the control circuit of the switch. R5, VD5 and
C3 form a simple resistor step-down voltage stabilizing circuit, which outputs a DC power of about 12V for the control circuit and other purposes. LED is a weak
light indicator, used to indicate the position of the touch switch at night , which is convenient for use. If low light indication is not required, use wires to
short-circuit the positive and negative pin solder joints of the LED.
    Integrated circuit A is a double D flip-flop, which is connected into a monostable circuit and a bistable circuit. The function of the monostable
circuit is to perform pulse broadening and shaping of the touch signal to ensure that each touch action is reliable. The bistable circuit is used to
drive the thyristor VS on or off. M is the touch electrode piece. If you touch M with your finger,
the voltage drop of the alternating current leaked from the human body on the resistor R2 will enter pin 3 of A, which is the CP1 end of the monostable circuit, causing the monostable circuit to flip into
a transient state , its output terminal Ql, or pin l, jumps from the original low level to a high level. This high level charges Cl through R3, causing
the potential of pin 4, or pin Rl, to rise. When it rises to the reset level, the monostable state The circuit is reset and pin 1 returns to low level. Therefore, every
time the electric chip M is touched, pin l outputs a positive pulse of fixed width. This positive pulse will be directly added to pin ll, which is
the CP2 terminal of the bistable circuit, causing the bistable circuit to flip once, and its output terminal Q2, or pin 13, will change once. When pin 13 is at
high level, the gate of vs gets a positive trigger current through R4 and is turned on, and the lamp H lights up. At this time
, the voltage across capacitor C3 will drop to about 3V, and the light-emitting tube LED will go out, but A can still work normally. When pin l3 outputs low level
, vs loses the trigger current. When the alternating current crosses zero, it turns off and the light goes out. At this time, the voltage across C3 can return to 12V, and
the LED lights up for weak light indication. It can be seen that every time the electrode sheet M is touched,
the action of "turning on" or "turning off" the light can be achieved.