Simple fade-in and fade-out switch circuit (2)

The last one adopts the two-wire connection method of gradually clearing/brightening switch circuit , which is relatively simple during circuit installation.
When you need to turn on the light, push the switch S upward to connect
the 2V positive power supply to R. Charging the capacitor (1),
the voltage across C gradually increases, so VT2 gradually becomes
conductive, the equivalent resistance of the high-power
tube VT1 gradually decreases, and the lamp E gradually becomes brighter from dark.
When C is fully charged , the brightness of the lamp will no longer change
. When turning off the light, move s downward, C stores
the charge P R; discharge to VT2, the lamp can still maintain
light, but the brightness will gradually dim over time, when (-charge When the discharge is basically completed, the light will be completely extinguished.
v r1 should use high back-voltage and high-power NI, N transistors , and there are no special requirements for other components.