Delay switch circuit

The variable delay switch circuit introduced here is that when a micro switch is pressed manually, the power supply is turned on to supply power to the circuit. After a certain period of time (which can be set), the power supply is automatically cut off and the power supply to the circuit is stopped. To achieve the above functions, intelligent devices can be used to complete it, or all-hardware digital circuits can be used to complete it. Although intelligent devices are simple, their anti-interference ability is not as good as the latter digital circuits, so for some simple functional circuits with harsh environments, digital circuits still have their due position. The variable delay switch circuit introduced here is completed with a digital circuit, as shown in the figure below. In the figure below, IC1CD40106 is a COMS6 inverter, and IC-1A, IC-1B, resistor R1 and micro switch in the figure form a bistable circuit. IC2CD4060 is a 14-bit binary serial counter/divider, which consists of two parts, one is a 14-level divider, and the other is an oscillator. The 9th and 10th pins of the oscillator work together with the external RC circuit to complete the setting of a given oscillation frequency. Although CD4060 has 14 counting stages, it only has 10 terminals, Q4~Q10, Q12~Q14, but 4 terminals, Q1, Q22, Q3 and Q11, are not led out. In the figure below, only Q14 terminal is used, which is also the last frequency division terminal and has the longest counting time. CD4060 (12) pin is RST terminal, which is a common reset terminal (RST). As long as a positive pulse or high potential is added to the RST terminal, the output of the counter can be all "0" level, and the oscillator is forced to stop oscillating at the same time, so the RST terminal can be called the reset terminal. CD4060 (11) pin, i.e. P1 terminal, is the counting input terminal, which counts incrementally under the action of the falling edge of the (clock) pulse. The CD4060 is a fully static operation. With the basic functions of the above IC, the working principle of the circuit in the figure below is easy to understand.
　　Circuit working process: When the micro switch S1 in the figure is manually touched, the input terminal ① of IC-1A is high level. After the high level is inverted twice by IC-1A and IC-1B, it is still output from the ④ pin of IC-1B. The high level is added to the input terminal ① of IC-1A through R1, so that the ④ pin of IC-1B remains at a high level (i.e. stable state). The high level of the ④ pin of IC-1B is output in two ways, one is added to the power supply terminal VDD of IC2CD4060 to start CD4060, and the other is added to the gate of MOS tube Q1 to turn on Q1. As a result, the power supply +6V supplies power to the A and B terminals.

At the moment when the micro switch S1 is touched, the high level output by pin ④ of IC-1B is differentiated by the differential circuit C3R2, and its peak (high level) is added to the clear O terminal (RST) of CD4060 to reset the CD4060 count. At this time, the counting output terminal Q of CD4060 is all zero, waiting for re-counting.

Once IC2CD4060 adds a high level to VDD and a reset pulse to RST, the pulse signal of the RC oscillator is directly added from point C to the (11) pin of CD4060, i.e., the Pl counting input terminal. At this time, CD4060 officially starts counting. After the counting is divided by 14 levels, the Q14 terminal outputs a high level, which is added to the input terminal ⑤ of the inverter IC-1C, and outputs a low level from the ⑥ pin after inversion. The low level forces the high level of the input terminal ① of IC-1A to be bypassed. As a result, the ① pin of IC-1A turns to a low level again, prompting the bistable to change state. The ④ terminal of IC-1B returns to a low level, Q1 is cut off, the power supply AB terminal stops supplying power, and CD4060 also stops working. Wait for the secondary switch timing.

When switch S1 is triggered, the +6V power supply time to the external AB terminal is determined by R4 and C4. Different R4 and C4 determine the delay of the switch. According to actual measurement:

When C4=0.47μF, when R4=10kΩ, the delay is 1 minute and 27 seconds; when R4=100kΩ, the delay is 11 minutes and 6 seconds; when R4, 1MΩ, the delay is 1 hour and 46 minutes. It can be seen that as long as the fixed capacitor C4 value remains unchanged and R4 is replaced by a potentiometer, a continuous variable timer can be made, which is very convenient to use.

Note: When the circuit is applied, you only need to add various application loads to the AB end of the circuit to complete the required timing function. For example, by connecting a wireless power supply chip to the AB end, you can complete the function of timing power transmission; by connecting an optocoupler and a bidirectional thyristor switch, you can control the operation of various AC power supplies at a fixed time.