Use HN911L to make induction lighting

It is a simple capacitor step-down half-wave rectification and voltage stabilizing circuit composed of VD1, VD2, Cl, and C2. After power is applied,
a DC voltage of about 12V can be obtained at both ends of the capacitor C2, which is used by the delay circuit composed of transistors VT1-VT3. This DC voltage is then
secondary stabilized by VD3 and filtered by capacitor C3 to obtain a stable DC voltage of about 6V, which is used to power the integrated module HN911L. When HN911L
does not detect an infrared signal, pin 2 outputs high level , vri is cut off, VT2 and VT3 are also cut off, vs is turned off, and the lamp
H does not light up.
    When someone is walking nearby, the infrared rays emitted by the moving human body are received by the infrared sensor inside the module. After being processed by the
internal , pin 2 outputs a low level. At this time, the PNP tube VTI is turned on, and the 12V positive power supply passes through VT1 , VD4
quickly charges the capacitor C4, and sends it to the base of VT2 through R4, so that VT2 and VT3 are quickly turned on. The thyristor VS
obtains the trigger current through VT3 and R5 to turn on, and the lamp H is lit immediately. As long as there are people nearby, the lamp H will
remain on. After the person leaves, pin 2 of the module will return to high level and VT1 will be cut off. However, since the charge stored in C4
can be discharged to the base of VT2 through R4, the light H can still be kept on. After about tens of seconds, the charge of C4 is basically
discharged, which is not enough to keep VT2 and VT3 on, VT2 and VT3 are cut off, and VS loses the trigger current. When the alternating current crosses zero
, it turns off and the lamp H goes out.
    The delay time of the circuit is mainly determined by the discharge time constant of R4 and 04. In addition, the resistance of R3 and the
amplification factor of VI2 and VT3 also have an impact on the circuit delay time. Appropriately adjust the resistance of resistor R4 to obtain a suitable delay time. This
circuit can be used for automatic lighting in bathrooms, stairways, etc.
    The photoresistor RO and the adjustable resistor RP connected between pins 4 and 5 of the module form the light control circuit of the lighting lamp . During the day,
because RO is exposed to light, its resistance is very low, which greatly reduces the gain of the module's internal amplifier. At this time, the module's pin 2 has no level
output, and the transistor VT1 will not be turned on, so the lamp H will not be lit during the day. . At night, the RO resistance becomes higher and
has little effect on the gain of the module's internal amplifier, so the module can work normally. Adjusting the potentiometer RP can adjust
the light control sensitivity of the circuit.