Function of module relay and form of additional circuit

Relay is an automatic switch device with isolated function. It is widely used in remote control, telemetry, communication, automatic control, electromechanical integration and power electronic equipment. It is one of the most important control components. The relay generally reflects the input variables (such as current, voltage, power, frequency, impedance, temperature, pressure, speed and light) of the induction mechanism (input); to the controlled circuit on and off control actuator (output) between the input part; and the output part of the relay, and are coupled to the input isolation function, treatment and mechanism of the middle part of the output (driver). Summed up as a control element, the relay module has the following several functions: the expansion of the control range: for example, relay contact control signal reaches a certain value, can according to the different forms of contact groups, and change the connection, disconnection, multichannel circuit. The amplification: for example, sensitive relay, intermediate relay, with a very small amount of control circuit can control the power of the great. The integrated signal: for example, when a plurality of control signals according to the provisions in the form of multi input winding relay, through comparison, control effect to the predetermined. Auto monitoring, remote control, automatic device: for example, the relay and other electrical appliances, can form a program control circuit to realize automatic operation. The relay is a common element in electronic circuit, electronic switch composed of transistors, relays and other components of the driving circuit, often have to add some additional circuit to change the operating characteristics of relay protection or. The additional circuit of relay mainly has the following three forms: 1. relay series RC circuit: this form is mainly applied to the rated work voltage of relay is lower than the power supply voltage circuit. When the circuit is closed, the relay coil will generate electromotive force because of the phenomenon of self inductance, which will hinder the increase of the current in the coil, thus increasing the pull in time. After the RC circuit is connected in series, the pull in time can be shortened. The principle is the closed circuit of the moment, the voltage across the capacitor C can not be regarded as mutations in short circuit, the power supply voltage to the coil so that the ratio of the relay coil rated voltage high, thereby speeding up the increase of the current in the coil speed, quickly pull the relay. After the power is stable, the capacitor C does not work, and the resistor R acts as a current limiting device. 2. relay parallel RC circuit: the closed circuit, when the current is stable when the RC circuit does not work, disconnect the circuit when the relay coil and the induced electromotive force generated due to the inductance, RC circuit, the current in the coil attenuation slowed, thereby prolonging the relay release time to delay action. 3. relay parallel diode circuit: mainly for the protection of transistors and other driving components. When the map in VT by the guide for biantong transistor cut-off when current flows through the coil of the relay will decrease rapidly, then the coil will produce electromotive force and power supply voltage superposition high after the VT C and e between the two poles, the transistor breakdown, parallel diode, the positive guide electromotive force clamp located in the coil diode voltage, the value of silicon tube is about 0.7V, the Ge tube is about 0.2V, so as to avoid the breakdown of the driving transistor components. Parallel diode must pay attention to the polarity of the diode can not be connected, otherwise it is easy to damage transistors and other driving components. .