Practical delay light circuit (1)

It is a practical delay light controller suitable for use in stairways, walkways and toilets. Press
the switch SB once and the light will light up for a few minutes or even more than ten minutes, and then go out on its own.
    VDl-VD4, vs, LED, R,
and have formed a simple bridge rectifier, step-down
and voltage stabilizing circuit. Normally, the capacitor [', and
C are full of r charge, the transistor VT?
is cut off, and the thyristor VT1 is not available. The trigger
current is in the off state. At this time,
the light-emitting diode I.ED lights
up the indicator switch, and the light bulb E does not
light up. When you need to turn on the light, just press SB and C. The stored charge passes through SR and R. Inject the base of VT2
, VT2 is turned on, the thyristor VT1 is turned on because the gate obtains the trigger current through the c'e pole of VT2, and the lamp E
lights up. At the same time c. The stored charge is quickly discharged through Sh. After releasing SB, due to C. The charging current of 9V
voltage at both ends to (1. charging, c) can maintain VT2 to continue to conduct, so U VT1 can still remain
on , and the lamp E still shines. When c. is fully charged, VT2 changes from the conducting state to Turns to the cut-off state, VT1 loses
r trigger voltage, turns off when the alternating current crosses zero, and the light F goes out. The delay time of the circuit is mainly
determined by the charging time constant of R., (1-, in addition, vs. the voltage stabilization value, The trigger sensitivity of VT] and
the electric power of the bulb E also have an impact on the delay time. There are no special requirements for the components of this circuit, C,, C. Use ordinary
CD1116V type electrolytic capacitors.
    Due to the delay time, there are many factors, so after the circuit is installed, you can use the stopwatch method to measure the delay time of the circuit to see if it is suitable for use. If it does not meet the requirements, you can adjust the value
by increasing or decreasing the value of the capacitor c. or the resistor R.
If the delay time K is large, the delay time K will be short. If it is used for stairway lights, the delay time can
be adjusted to about E irn, n; if it is used for Jfiij, the delay time should be adjusted to LO for several minutes. The display of the controller Advantages:
The circuit is simple, and the connection between the controller and the bulb is two-wire, so the installation is very convenient. It can directly replace the common
wall switch without having to change the original indoor wiring.