Button control switch 4017 digital circuit chip

Key control switch 4017 chip digital circuit
This is a key control switch circuit composed of a decimal counter 4017.The schematic diagram of the circuit is shown in the figure.

Key control switch
Principle introduction

After the power is turned on, C1 is charged through R1, and it is fully charged in a very short time.R2 and C2 form a power-on reset circuit. When the power is first turned on, C2 can be regarded as a short circuit, so the RST reset terminal of pin 15 of U1 is at a high level, and U1 is reset. In a short time, C2 is charged.Pin 15 returns to low level. At this time, Q0 outputs a high level, which is added to the base of V1 through R3, V1 is turned on, relay K is pulled in, and LED1 is lit, indicating that the controlled circuit is connected.The Q1~Q9 output terminals of U1 are all low level.

When the switch S1 is pressed, C1 is rapidly discharged, the 14th pin of U1 gets the rising edge of the pulse, triggers U1 to start counting, and the output of Q0 changes from high level to low level.Q1 outputs a high level, and Q2 maintains a low level. At this time, V1 is turned off, the relay K is released, and LED1 is turned off, indicating that the controlled circuit stops supplying power.After switch S1 is released, C1 is fully charged again.

When the switch S1 is pressed again, C1 will discharge again, and the 14th pin of U1 will get the counting pulse again, triggering U1 to count again.The high level is added to the RST reset terminal of pin 15 of U1 through VD1 to reset U1, so the output of Q0 becomes a high level, Q1 and Q2 output a low level, V1 is turned on again, the relay K is pulled in, LED1Lights up, indicating that the controlled circuit is energized again and starts to work.Therefore, every time S1 is pressed, the output state of Q0 is reversed once, and the controlled circuit is turned on or off once.

Experimental tips

During the working process of the circuit, when S1 is pressed, C1 will be discharged. When S1 is released, after a short period of time, C1 will be fully charged again, and the 14th pin of U1 will be low level.During this time, any mechanical jitter on switch S1 will also not generate a second technical pulse, thus acting as an anti-jitter.Other outputs of 4017 are not used and can be left floating.