Touch delay light switch circuit (8)

It is a touch-type delay light switch with good power reduction . Its circuit characteristics are: extremely small static power consumption;
the switch only has root terminals for external use, and can directly replace ordinary switches.
    A in the picture is a novel precision voltage stabilizing integrated circuit T1.43 ] Or AS431, which looks like a sealed
tube. Normally
there is no conduction between the anode and the cathode, the thyristor
VT1 is broken, and the lamp
F does not light up. When a human hand touches
M, the human body leaks current
through R. ,R. Divide the voltage and
add it to the control
pole of F1,431, causing TL131
to turn on quickly, and 20V DC flows to C. through R, TI.43l and VD6. Charging, through R, connects the base of VT2,
causing VT2 to conduct, VT1 obtains the trigger current and turns on, and the lamp E is energized and emits light. After the eight hands leave M,
the charge stored in Ct can be discharged to v r2 through R:, which keeps VT2 on, so the lamp E will not
go out. Until the C-discharge current gradually decreases, when it is not enough to maintain the conduction of VT2, VT1 loses the trigger
current. When the alternating current crosses zero, it breaks off and the lamp E goes out.
    The delay time of the circuit is mainly composed of G and R. The discharge time constant is determined. In addition, the trigger sensitivity of VT1
and the amplification p value of VT2 have a great influence on the delay time. It is best to use Mitsubishi CR2AM-12
or CR3AS-12 micro -triggered unidirectional thyristors for VT1, which can be switched on as long as they have a contact current of 0_irnA;
VT2 should use Samsung TIP50 or MPSA-14 type thyristors, which require p /50, at this time the delayed stripping is about 70s
; if p≥250, R. Using 4 7Mn H10, the delay time reaches about 5m,n.