One of the touch lighting switch circuits

The touch-type lighting switch is an electronic switch that can switch on and off by touching the conductive sheet with your hand. It can be used in
circuits such as desk lamps.
(1) One of the touch lighting switch circuits
    . The circuit is shown in Figure 2-51. It uses the LS7232 imported special touch voltage regulation integrated circuit as the control element. BH
is a special power supply voltage regulator protector, which can ensure that the circuit can still work reliably when the grid voltage fluctuates by ±20%. To ensure safety
, the resistors Ri, R2, R3, and R4 in the circuit cannot be replaced by one resistor.
    The conductive sheet M can be connected to metal parts (such as desk lamp housing). When the hand touches M quickly (t<500ms), the light EL
turns on and off. When the hand touches M continuously (t>500ms), the brightness of the light gradually changes from the brightest to the brightest and then gradually brightens again
. This cycle repeats. until your hands are released. At the same time, the integrated circuit has a memory function inside, which can store the brightness level when the hand is released into
the circuit. The next time you turn on the light, the light will remain at the originally set brightness.