What is a Time Delay Switch?

Delay switch is a new type of automatic delay electronic switch developed to save power resources, saving power and convenience. Mainly used in stairwells, bathrooms and other places.

Chinese name: Delay switch
Foreign name: Time delay switch

Types of: Touch delay switch, sound and light control delay switch
Application: Stairwells, bathrooms, etc.

Composition of delay switch circuit

The acousto-optic delay switch circuit is composed of a power supply circuit, a sound control circuit, a light control circuit, a delay and an electronic switch circuit ^[1] .

Circuit Analysis of Delay Switch Acousto-optic Control Delay Switch Circuit

The circuit is divided into main circuit, power circuit, light control circuit, sound control circuit, logic level inversion and trigger circuit, delay circuit and other unit circuits:

1) Main circuit and power circuit

The main circuit consists of rectifier bridges D1 to D4 and thyristor T1. T1 is the switching actuator. After the thyristor T1 is triggered to be turned on, the circuit is turned on and the incandescent lamp is illuminated. When there is no trigger signal on the control pole of the thyristor, the thyristor T1 is blocked in the forward direction and the circuit is turned off. The function of the power circuit is to provide power to the circuit so that the circuit can work normally. It is composed of R1, D5, C1, C2 and other components. It is a simple DC stabilized power supply that supplies power to the whole machine. The AC 220v is first bridge-rectified into pulsating DC, and then reduced by R1, C1 filtering to smooth the waveform, and finally stabilized DC power is obtained by the voltage regulator diode, which is an electret microphone (MIC). , Amplifier circuit (VT), logic level inversion and trigger circuit (CD4011 chip), etc. ^[1] .

2) Light control circuit

It is mainly composed of R5 and RG. The on and off of the thyristor in the circuit depends on the presence or absence of the control pole signal. The resistance of the photoresistor RG changes with the intensity of the light.When the light reaches a certain intensity, its resistance becomes small enough to make the (13) pin of IC (a) at a logic low level after dividing with R5. 13) The NAND gate where the pin is located is blocked. At this time, whether or not the sound signal is input, the (10) pin of IC (d) is low level, and the thyristor is blocked in the forward direction. With the decrease of the light intensity, the RG resistance value gradually increases, and the potential of the (13) foot gradually rises. When the potential of the (13) foot rises to a logic high level, the door opening condition is met, and the voice control starts to work. Whether the (11) pin is inverted depends only on whether the potential of the (12) pin (input terminal of the sound control circuit) of the IC (a) reaches a logic high level ^[1] .

3) Sound control circuit

It consists of a microphone MIC, a transistor T2, a capacitor C3, and resistors R2 to R4, etc. Among them, the MIC is an acoustic detection element. When the ambient sound signal is weak, the transistor T2 is in a saturated state, the IC (12) pin is low, and the (10) pin is also low, and the thyristor T1 is blocked. When the ambient sound signal reaches a certain intensity, the MIC pickup output is coupled to the base of T1 through C3, so that the potential of the collector, that is, the IC (12) pin changes with the sound intensity, and when (12) pin is at high power Usually, because the (13) pin is already at a high level and the NAND gate inversion condition is satisfied, the (11) pin jumps to a low level ^[1] .

4) Logic level inversion and trigger circuit

It consists of four-two input NAND IC (CD4011) and R7. It can be seen in the figure that when daytime or the light is very bright, the (13) pin of the NAND gate IC (a) is low level, and the output of the (11) pin is high level.After IC (b), IC (c) The level conversion of IC (d), the output of (10) pin of IC (d) is low level, thyristor T1 is not triggered, and the light is not on; when the ambient light is dark, the (13) pin of IC (a) When it is a logic high level, it provides the conditions for IC (a) to flip. Whether IC (a) is flipped or not is controlled by the level of the IC (a) (12) pin (input terminal of the sound control circuit). When a sound signal is input to make pin (12) of IC (a) high, the output (11) pin jumps to low level, (3) pin jumps to high level and charges C4 via D6. The voltage on C4 keeps rising. When the voltage on C4 rises to the logic high level of IC, pin (4) becomes low level, and pin (10) outputs high level, which is added to the control electrode of thyristor T1 via R7. Thyristor T1 is triggered to turn on ^[1] .

5) Delay circuit

It consists of R6, C4, D6 and other components. Combining the analysis of the sound control circuit and the main circuit, when the thyristor T1 is triggered to be turned on, the voltage on C1 decreases, the MIC pickup sensitivity decreases, T2 resaturates, (11) is high, and (3) becomes low. Level, due to the isolation of D6, the voltage on C4 remains high on pins (5) and (6), and pin (10) is also high. The voltage on C4 is discharged through R6 until the voltage on C4 drops to the logic low level of IC, and the (10) pin becomes low level, and thyristor T1 is blocked in the positive direction when the voltage between the positive and negative poles crosses zero, and C1 The voltage on the MIC is increased again to recover the pickup sensitivity, and wait for the next sound control signal input.The time for the potential of the IC (5) and (6) pins to drop from high to low is the maintenance time of the switch on. Determined by the values of C4 and R6 ^[1] .

How delay switches work

The electret microphone MIC is used for the sound detection in the switch circuit, and the transistor T2 is used as the amplifier. When there is no sound, T2 is in a saturated conduction state. When there is sound, the microphone MIC receives the sound signal, which can make T2 cut off. 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. Except that one of them is directly used as the discrimination circuit of 2-input NAND gate in CD4011, the other three are connected as inverters for amplifier. D6, R6, and C4 form a delay circuit. The switch uses thyristor T1. Diodes D1 ~ D4 and thyristor T1 form a controllable rectifier circuit. When T1 is on, the lamp LAMP lights up; when T1 is off, the light bulb goes out ^[1] .

During the day, the photoresistor RG is in a low resistance state when exposed to light, and the CD4011 (13) pin is always low. At this time, regardless of whether the CD4011 (12) pin is high (no sound makes T2 cut off) or low (no sound T2 is saturated and turned on), the NAND output (11) pin is always high. After three inversions, the (10) pin output is low, the thyristor T1 is turned off, and the light bulb is off. It can be seen that the light bulb has not been lit during the daytime due to the light resistance of the photoresistor RG ^[1] .

Brief introduction of delay switch performance

The delay switches include touch delay switches, sound and light control delay switches, and the like. Just touch the touch pad of the switch or give the sound signal to illuminate automatically. When a person leaves, it will automatically shut down within 30 to 75 seconds, which is highly recommended for the National Energy Department.

Basic principle of sound and light delay switch; sound and light delay switch is made up of several sound control switches, light control switches and light bulbs in series. When there is light, the photosensitive switch is opened, and when there is no light, the photosensitive switch is closed. Then when there is sound. The sound-sensitive switch is closed. Thereby, a pathway is formed. Light up the lamp.

The touch delay switch uses the same principle as the test pen, that is, a large resistance is connected in series between the human body and the power supply. In this way, a low voltage current is formed through the body (the voltage is low, but the current is not necessarily small ), Finally flowing into the ground, forming a trigger loop, so that you can trigger the delay switch to start timing, and the main circuit of the electric light is turned on, and the light is on.

Installation location of delay switch

It is mainly used in schools, residential buildings, complex buildings, office buildings, large shopping malls, banks, hotel rooms, villas, public corridors, underground garages, etc. Delay switches should be installed at the elevators and stairs at each floor, which is conducive to saving Electrical energy. Delay switch can be used in some places with public use.

Delay switch symbol rules

When the delay switch is placed vertically, the movable contact is normally open on the left of the static contact, and the movable contact is normally closed on the right of the static contact. When the delay switch is placed horizontally, the moving contact is normally open under the static contact, and the moving contact is normally closed under the static contact.

The action of the delay switch moves in the direction of the arc.