Use NE555 to make a single-button touch light switch

The circuit for making a single- touch light switch using NE555 is shown in Figure 3-4. This circuit is very similar to the circuit introduced in the previous section . Its power rectifier part is exactly the same, that is, no matter whether the thyristor VS is in the on state or the blocking state, both ends of can stably output 6V DC voltage to provide the time base. Circuit A uses electricity. Just change the touch electrode piece from the original two pieces into one piece, connect the trigger end pin 2 of the time base circuit to the value breaking end pin 6, and then connect it to the touch electrode piece M through the high resistance resistor R4 .     When the circuit is first powered on, the state of the time base circuit is random. Assume that the initial state is the reset state, pin 3 outputs low level, vs is in the blocking state, and the light H does not light up. When you need to turn on the light, just touch the electrode piece M, and the clutter signal induced by the human body is simultaneously added to pins 2 and 6 of the time base circuit through R4. The positive half-cycle signal has no effect on pins 2 and 6 at this time, and The negative half-cycle signal can trigger pin 2, causing the circuit to quickly flip and set, and pin 3 will output a high level. VS will get the trigger current and turn on, and the lamp H will light up, and the circuit can always maintain this state. When you need to turn off the light, you still touch the electrode piece M. The same clutter signal induced is added to pins 2 and 6 of the time base circuit at the same time. However, at this time, the negative half cycle of the signal affects both pins 2 and 6. It does not work, and the positive half-cycle signal can trigger the threshold terminal of pin 6, the circuit quickly flips and resets, pin 3 outputs low level, vs loses the trigger voltage, when the alternating current crosses zero, it turns off, the lamp H goes out, and The circuit can always maintain this state.     From the above analysis, it can be seen that every time a human hand touches the electrode sheet M, the state of the circuit changes once, that is to say, if you touch it once, the light will be on: if you touch it again, the light will be off. The nozzle is very convenient to use. But you need to pay attention when using it. When turning on and off the light, just touch M with your hand. Do not hold M for a long time. If you hold it down for a long time without letting go, the light H will flicker and jitter.