What is km in the street light automatic control switch circuit

In the automatic control switch circuit of street lights, KM usually refers to the relay. A relay is an electronically controlled switching device, which controls the switching state of the circuit through electromagnetic attachment and release. In the automatic control system of street lights, the relay plays the function of controlling the switch of the street lights.

Relays consist of electromagnets and contacts. When the electromagnet of the relay is energized, the electromagnet will generate a magnetic field that attracts the contact to close and energizes the circuit; When the electromagnet is de-energized, the magnetic field disappears and the contacts open, disconnecting the circuit. By controlling the energizing and power-off of the relay, the automatic on/off control of the street lamp can be realized.

In the automatic control system of street lights, KM is usually a switching element that controls the relay. When KM is closed, the relay is energized and the street light is on; When KM is disconnected, the relay is powered off and the street lights go out. The closure and disconnection of the km can be achieved by different control methods.

One common way to control is light control. When the ambient light intensity is lower than a certain threshold, the resistance of the photosensitive element increases, so that the km is closed, the relay is energized, and the street light is lit up; When the ambient light intensity is higher than a certain threshold, the resistance of the photosensitive element decreases, so that the km is disconnected, the relay is powered off, and the street light is extinguished. In this way, the street lights can be automatically controlled according to the ambient light intensity.

Another common form of control is time control. Elements such as clock circuits and timers are used to set the switching time of street lights. When the set time arrives, the timer is triggered, so that the km is closed, the relay is energized, and the street light is on; When the set time is over, the timer is triggered again to disconnect the km, the relay is powered off, and the street light is extinguished.

In this way, the switch of the street light can be automatically controlled according to the set time.

The relay plays a key role in the automatic control system of street lights, which realizes the automatic switching of street lights by controlling the switching state of the circuit. Through reasonable control methods and parameter settings, energy-saving and intelligent street lamp control systems can be realized, and the use efficiency and management level of street lamps can be improved.

km is the graphic text symbol of the AC contactor.

In two parts:

1) It is a photosensitive circuit, which is used to generate a switch control signal, and the circuit forms are diverse, which can be referred to on the Internet;

2) The switching circuit that controls the mains on-off is mechanical such as relays, and there are also (single, bidirectional) thyristors as switching components, because the thyristors work in the alternating current environment, most of them use the photocell coupling mode to receive the control signal --- the signal output by the photosensitive circuit;

You can choose the circuit according to the load power--- opto-coupled bidirectional thyristor circuit (online).

In the above figure, the photosensitive element controls the relay according to the light intensity, and the relay J controls the automatic switch of the street light.

As shown in the figure below, the 220V alternating current passes through the bulb H and rectifies the full bridge, and then becomes a DC pulsating voltage, which is added to the VS and R branches of the thyristor as a forward bias voltage. During the day, when the brightness is greater than a certain extent, the photodiode D presents a bottom resistance state of 1K, so that the triode V is cut-off, and its emitter has no current output, and the unidirectional thyristor VS is blocked due to no trigger current. At this time, the current flowing through the bulb H does not emit light.

The resistor R1 and the regulator diode DW make the triode V bias not exceed and protect the triode. At night, when the brightness is less than a certain level, the photodiode D presents a high-impedance state of 100K, so that the triode V is positively conducted, and the voltage of the emitter is about to make the thyristor VS trigger the conduction, and the bulb H emits light. RP is a brightness selector that switches early in the morning or late in the evening.

Installation & Commissioning:

When installing, put the welded printed board into a transparent plastic box and fix it, connect it in series with the controlled electric lamp, and let it face the brighter space in front of the canopy or the lighting window of the house, and avoid direct irradiation of the night light within 3 meters. The debugging should be carried out in the evening, and the size of the RP resistance value should be adjusted so that the controlled lamp H is lit at the appropriate brightness.

One: A two: 1: Automatic switch.

2:3: The autumnal equinox is equal in length to day and night, and the lights consume electricity at night.

The coil does not consume 25w=

The light does not light up during the day and the coil consumes power, 36V*

Total power consumption in a day and night.

Fourth: the protection circuit can not affect the original function of the circuit, and the current of the relay coil can not be less than 40mA when there is light

36V 40mA = 900 so the protection resistance is not greater than 900

2.Small 1 automatic switch Small 2 negative pole is connected to the protection resistor, and the other end of the protection resistor is connected to the photoresistor. 3. 4.I don't know if the watchtower owner adopted the pen hard to calculate.

The figure is not drawn, and the right side of the coil is connected to the right side of the protection resistor. The left side of the resistor is connected to the right side of the photoresistor.

The protection resistance is calculated as 36V, 40mA is not more than 900 ohms.

Answer: <>

Solution: (1) The electromagnetic relay works by using the magnetic effect of electric current;

(2) As shown in the figure, when the light irradiates the photoresistor RG, its resistance value becomes smaller, resulting in the reduction of the divided voltage In this way, the voltage at the input end of the non-gate circuit becomes larger, so that the voltage at the output end of the non-gate circuit becomes smaller, because the voltage at both ends of the relay is U1 during the day and U2 at night, so U1 U2 When the light becomes weaker, the resistance of the resistor RG becomes larger, the voltage at the input end of the non-gate circuit becomes smaller, the voltage obtained by the relay becomes higher, and the street lamp is lit In order to make the street lamp automatically turn on the switch when the sky is darker, the resistance r should be increased, The voltage of r is increased, the input voltage of the non-gate circuit is increased, the voltage obtained by the relay is everywhere, and the street lamp is not lit