Low power consumption timing switch circuit

(I) Introduction to the circuit principle: This timing circuit is equipped with an electronic switch composed of F1, F2 and VT1, which can
reduce the quiescent current of the 555 to 1-2riA. When the power is first turned on, the voltage on G cannot change suddenly, causing the F2 gate circuit to be at a high level and the Fl output to be locked at a low level
. VT1 is cut off, making the quiescent
current of the entire circuit very small. When the timer switch AN is pressed.
A negative polarity pulse appears at the input terminal of Fl.
Fl output is high level, VT is turned on, and 555
has power supply voltage. At the same time, a negative pulse is
applied to the ② pin of 555 to set the 555. K
pulls in and the timing starts. Timing time Td—
1. lR4 C3. The timing length can be changed by adjusting
the time constant of Shuc{.
    (2) Component parameter selection
The selection of components is shown in Figure 3-44, and there are no special requirements.
    (3) The low-power timing switch circuit is shown in Figure
3-44.