The working principle of the delay switch, the working principle of the delay relay

In the switching circuit, the sound detection adopts the electret microphone MIC and the triode T2 to form an amplifier. When there is no sound, T2 is in a saturation conduction state, and when there is sound, the microphone MIC receives the acoustic signal, which can make T2 cut. The brightness detection is done by the photoresistor RG.

The CMOS digital integrated circuit CD4011 used in the circuit contains four 2-input NAND gates. In CD4011, except for one of which is directly used as 2 input terminals and NAND gates as the discriminant circuit, the other three are connected to the inverter as amplifiers. D6, R6, and C4 form a delay circuit.

The switch adopts thyristor T1. The diode D1 D4 and the thyristor T1 form a controllable rectifier circuit, and when T1 is turned on, the lamp lamp lights up; When T1 is cut-off, the bulb goes out.

During the day, the photoresistor RG is in a low-impedance state when illuminated, and the CD4011(13) pin is always low. In this case, regardless of whether the CD4011 (12) pin is high (there is a sound to cut off T2) or low (there is no sound T2 saturation conduction), the NAND gate output (11) pin is always high. After three inversions, the output of pin (10) is low, the thyristor T1 is cut-off, and the bulb is not lit.

It can be seen that due to the light action of the photoresistor RG, the bulb will not light up during the day.

This should be explained to you from the principle of leakage switch.

I'll go find some information to copy to you first, and then I'll tell you why the grounding system can also be used.

Copy: Generally, when all the wires of the same circuit pass through the same current transformer (also called zero-sequence transformer), the secondary of the transformer has no output, that is, the zero-sequence current of the circuit is zero. When there is leakage in the line (leakage occurs below the transformer), the sum of the current vector through the transformer is no longer zero, and the secondary transformer will have output current, and leakage protection can be carried out by using this principle.

After reading the above, you also understand a little, in general, whether it is a grounded or ungrounded system, the total vector sum of several lines output is 0.

According to this principle, it is said that there is no distinction between the ground and the ground, as long as the vector sum is not 0 and the predetermined value is reached, your leakage protector will act.

Supplement: There is no load, but the circuit after you are grounded flows back to the neutral point of the transformer through the earth, and the branch that flows back is not flowing back through your leakage protector, that is to say, the sum of the electric vectors flowing in your leakage protector is no longer 0, so the protection action. In fact, you just need to figure out that as long as the current vector and the sum of the current flowing inside the leakage protector are not 0 and reach your set value, then your protection will act.

It's easy to understand. Is there anything else you don't understand?

The working principle of the delay relay is that when the time relay coil is energized, each delay contact acts instantaneously, and the contact is in a delayed set working state after the coil is powered off, and when the set delay arrives, the delay contact returns to the initial state.

The power-off delay type is due to its working state (no external working power supply is required during the delay process) and the control contact is engaged during the power-off delay process (the normally open contact should be kept on when it becomes on; The normally closed contact becomes open and should remain open) The conversion particularity (which is the opposite of the working state of the contact of the conventional energized time-delay time relay) to meet its control requirements.

The power-off delay time relay is composed of the earliest separation device (low delay accuracy and short delay time); At present, the corresponding programmable timing integrated circuit or CMOS counting and frequency division integration is used to complete the delay, which has the characteristics of high delay accuracy and long delay time. In order to meet the control occasions of long delay in power failure.

Power-off delay timeThe contact of the relay acts after the relay is energized, and after the relay is powered off, the delay time reaches the preset time and the contact returns to the original state.

The working principle of the power-on delay relay: the time-on delay contact is not active, and after the time-lapse time, the time-long delay contact is disconnected, and the time-open contact is closed. The use of energizing delay resistor capacitor charging delay circuit, that is, the resistor-capacitance principle (RC circuit) to achieve the delay function, the connection method is to use the normally open point if you want to delay the turn-on, and if you want to delay the disconnection, use the normally closed point.