Double button light switch circuit (11)

It is a two-button touch light switch made of rw¨a77s power integrated circuit. The circuit characteristics are the
same as J. Example is the same. The Fengji power supply is stepped down by transformer T, v]) 1-VD4 rectifier and C filter, and outputs 1 2V
DC voltage for TWH8778. usually. The control terminal EN of TWH8778 , that is, the ⑤ pin, has no voltage, the internal
switch circuit is disconnected, the relay K does not operate, and the lamp fi /f is on. If you touch the Ml "ten f" electrode with your hand,
the signal induced by the chip will turn on the transistor VT1. Make the ⑤ pin of the integrated block high level , the internal ten F switch
circuit is closed, that is, the ① pin is connected to the ② and ③ pins, the relay K is electrically closed, its moving contact point kl l0 is closed, and
the lamp E is energized and emits light. At this time
, the high level of pins ② and ③ will
be fed back to pin ⑤ of the control terminal through the resistor R. Therefore, even
after the human hand leaves the electrode sheet,
the switch circuit inside the integrated block can still remain closed
, so the relay can
be maintained Suction. When turning off the light, you only need to touch
the M2 "fixed" electric trigger. At this time,
the diode wr2 is turned on and the ⑤ pin of the control terminal of the integrated block
is short-circuited to the ground. Therefore, the internal switch circuit of the integrated block is disconnected, and the ② and @ pins are output. Low level, after IU breaks K and releases, contact kl jumps and does not recover, and the light turns off. t』At the same time, the low level of pins ② and ③ will be fed back through the resistor R, so that the control terminal pin ⑤ can still maintain a low level and   the circuit is always off even after the human hand leaves the Mv electrode sheet . The circuit requirements for triodes and relays are the same as those for F. Pi.