Use NE555 to make a two-button touch light switch (2)

The circuit is shown in Figure 3-3. The left part of the dotted line in the figure is the ordinary lighting circuit, and the right part is the two-button touch light switch made with NE555 .     VD1~VD4 form a bridge rectifier circuit, and vs and VD5 form the main circuit of the switch . When vs is on, the light is on: when vs is blocked, the light is off. When vs is in the blocking state, the 220V alternating current is rectified by VD1 ~ VD4, and a voltage stabilizing circuit is composed of R2, VD5 and CI. A DC voltage of about 6V can be obtained at both ends of Cl to supply power to the time base integrated block A. When vs is in the on state, the alternating current is rectified by VD1 ~ VD4, and forms a loop through vs and VD5 . A DC voltage output of about 6V can still be maintained at both ends of CI. Therefore, the DC operating voltage of the time base integrated circuit will not drop due to the conduction of vs.     The time base circuit A is connected here as an RS trigger. When the human hand touches the electrode sheet M1, the clutter signal induced by the human body is injected into the trigger end pin 2 of the time base circuit through R4, and is rectified by VD6 so that the trigger end pin 2 gets a negative Pulse trigger signal, the time base circuit is set, and the output pin 3 outputs high power. At this time, vs gets the trigger current from Rl and is turned on, and the lamp H is energized and emits light. When you need to turn off the lights, just touch the electrode M2 ​​with your finger. At this time, the clutter signal induced by the human body is injected through R5 and rectified by VD7, so that the 6th pin of the min value terminal of the time base circuit obtains a positive pulse trigger signal. The time base circuit Reset, pin 3 of the output terminal outputs low level, the forward trigger voltage provided by Rl is short-circuited to ground by R3 through pin 3 of the time base circuit, vs loses the trigger voltage, and when the AC power is too high, it is turned off and the light H goes out.