Relay is an electronic control device, it has a control system (also known as input loop) and a controlled system (also known as an output loop), usually used in automatic control circuits, it is a “automatic switch” that uses a smaller current to control a larger current. It plays the role of automatic adjustment, safety protection, conversion circuit and so on in the circuit.

The working principle and characteristics of relays

When the input amount (such as voltage, current, temperature, etc.) reaches the specified value, the controlled output circuit is turned on or off. It can be divided into two categories: electrical quantity (such as current, voltage, frequency, power, etc.) relays and non-electric (such as temperature, pressure, speed, etc.) relays. It has the advantages of fast action, stable work, long service life and small size. Widely used in power protection, automation, motion, remote control, measurement and communication devices.

Relay is an electronic control device, it has a control system (also known as input loop) and a controlled system (also known as an output loop), usually used in automatic control circuits, it is actually a “automatic switch” that uses a smaller current to control a larger current. Therefore, it plays the role of automatic adjustment, safety protection, conversion circuit and so on in the circuit.

Ultrathin relay and relay socket1

1. The working principle and characteristics of electromagnetic relay
Electromagnetic relays are generally composed of iron cores, coils, armatures, contact reeds, etc. As long as a certain voltage is added at both ends of the coil, a certain current will flow through the coil, resulting in electromagnetic effect, and the armature will overcome the tension of the return spring to the iron core under the action of electromagnetic force attraction, thereby driving the moving contact of the armature and the static contact (normally open contact) to close. When the coil is de-energized, the electromagnetic suction force also disappears, and the armature will return to its original position in the reaction force of the spring, so that the moving contact and the original static contact (normally closed contact) are closed. In this way, it is absorbed and released, so as to achieve the purpose of conduction and cutting in the circuit. For the “normally open, normally closed” contact of the relay, it can be distinguished as follows: the static contact that is in the open state when the relay coil is not energized is called the “normally open contact”; Static contacts that are in the on state are called “normally closed contacts”.

2. The working principle and characteristics of thermal reed relay
Thermal reed relay is a new type of thermal switch that uses thermal magnetic materials to detect and control temperature. It consists of a thermostatic magnetic ring, a constant magnetic ring, a reed switch, a thermally conductive mounting sheet, a plastic substrate and some other accessories. Thermal reed relays do not use coil excitation, but the magnetic force generated by the constant magnetic ring drives the switching action. Whether the constant magnetic ring can provide magnetic force to the reed switch is determined by the temperature control characteristics of the temperature-sensing magnetic ring.

3. The working principle and characteristics of solid-state relay (SSR).
A solid state relay is a four-terminal device with two terminals as the input terminal and the other two terminals as the output end, and an isolation device is used in the middle to achieve the electrical isolation of the input and output.

Solid state relays can be divided into AC type and DC type according to the type of load power supply. According to the switch type, it can be divided into normally open type and normally closed type. According to the isolation type, it can be divided into hybrid type, transformer isolation type and photoelectric isolation type, with the photoelectric isolation type being the most.

Second, the main product technical parameters of the relay

1. Rated working voltage
It refers to the voltage required by the coil when the relay is working normally. Depending on the type of relay, it can be AC voltage or DC voltage.

2. DC resistance
Refers to the DC resistance of the coil in the relay, which can be measured by a multimeter.

3. Absorb current
It refers to the minimum current that the relay can generate for the pull-in action. In normal use, the given current must be slightly greater than the pull-in current so that the relay can work stably. For the working voltage applied to the coil, generally do not exceed 1.5 times the rated working voltage, otherwise a larger current will be generated and the coil will be burned.

4. Release current
It refers to the maximum current at which the relay produces a release action. When the current in the closed state of the relay decreases to a certain extent, the relay returns to the unenergized released state. The current at this time is much smaller than the pull-in current.

5. Contact switching voltage and current
Refers to the voltage and current that the relay is allowed to load. It determines the size of the relay can control the voltage and current, and this value cannot be exceeded when used, otherwise it is easy to damage the contacts of the relay.