Working principle and characteristics of the relay.
Relay is an electronic control device, it has a control system (also known as the input circuit) and control system (also known as the output circuit), usually used in automatic control circuit, it is actually a "automatic switch to control a larger current with small current". Therefore in the circuit plays the automatic regulation, the security protection, the transformation circuit and so on.
1. The working principle and characteristics of electromagnetic relay
Electromagnetic relay is generally composed of iron core, coil, armature, contact etc.. As long as the coil ends with a voltage and current will flow through the coil in a, resulting in electromagnetic effects, the armature will attract the electromagnetic force to overcome the spring to return to the core rally absorption, thereby driving the armature static and dynamic contact (normally open). When the coil power, the electromagnetic force disappears, the armature will return to the original position in the spring reaction, the dynamic contact with the original static contact (normally closed contact). This pull and release, in order to achieve the circuit in conducting cutting purposes. For the relay "normally open and normally closed contacts", it can be to distinguish between: the relay coil is not energized in off the static state of contact, known as the "normally open contact"; in a static contact state called "normally closed contact".
2. The working principle and characteristics of the heat sensitive dry reed relay
The thermal sensitive dry reed relay is a new type of thermal sensitive switch which uses the heat sensitive magnetic material to detect and control the temperature. It consists of a thermal magnetic, permanent magnetic ring, reed thermal installation piece, plastic substrate and other accessories. Thermal reed without coil excitation, the magnetic force generated by the permanent magnetic ring drive switch. The permanent magnetic ring to the dry spring could provide the magnetic force is determined by the characteristics of the temperature control temperature magnetic ring.
3, solid state relay (SSR) working principle and characteristics
The solid state relay is a two terminal, and the other two terminals are the four end devices of the output terminal, and the isolation device is adopted to realize the electrical isolation of the input and output.
According to the type of load power supply can be divided into AC and DC type. According to the switch type can be divided into normally open and normally closed type. According to the isolation type can be divided into mixed type, transformer isolation type and photoelectric isolation type, with photoelectric isolation as the most. Two, the main technical parameters of the relay
1, rated working voltage
Is the voltage required by the coil during the normal operation of the relay. Depending on the type of relay, it can be AC voltage or DC voltage.
2, DC resistance
The DC resistance of the coil in the relay can be measured by the universal meter.
3, pull current
Refers to the minimum current relay can produce pull action. In normal use, given the current must be slightly larger than the operating current, so relay to work stably. And for the coil plus the working voltage, generally do not exceed the rated operating voltage of 1.5 times, otherwise it will produce a larger current and the coil burned.
4, the release of the current
Is the maximum current of the relay that releases the action. When the current state of the relay is reduced to a certain extent, the relay will be restored to release status is not energized. This current is far less than the current.
5, contact switch voltage and current
Is the voltage and current that the relay is allowed to load. It determines the size of the relay to control the voltage and current, can not exceed this value, otherwise it is easy to damage the relay contacts.
Three, relay test
1, measuring contact resistance
With the universal form of the resistance profile measurement, normally closed contact and fixed point of resistance, the resistance should be 0; and the normally open contact point and resistance to infinity. This can be distinguished from the normally closed contact, that is normally open contact.
2, measuring coil resistance
Available multimeter R * 10 ohm measurement relay coil resistance, so as to judge whether there exists the coil open circuit phenomenon.
3, measuring voltage and pull pull current
Find the adjustable regulated power supply and the current meter, to the relay input a set of voltage, and in the power supply circuit in series into the current meter to monitor. Slowly increase the supply voltage, hear relay voice, write down the pull in voltage and pull current. For the sake of accuracy, you can try several times and the mean value.
4, measurement of the release voltage and release current
Is the connection test as mentioned above, when the relay pull in occurs, and then gradually reduce the power supply voltage, when the relay again release sound when the voltage and current of the mind, may try a few times and achieved the average release voltage and current release. In general, the release of 10~50% voltage relay about the pull in voltage, if the voltage is too small (the release of the pull in voltage of less than 1/10), cannot be used normally, it will threaten the stability of the circuit, not reliable.
Four, the relay of the electrical symbol and contact form
Relay coil in the circuit with a rectangular box symbol, if the relay has two coils, draw two parallel rectangular frame. At the same time in the rectangular box or rectangular box next to the symbol of the relay of the relay J". There are two ways to express the contact of the relay: one is to draw them directly on the side of the rectangular frame, which is more intuitive. The other one is in accordance with the needs of circuit, the control circuit of individual contacts to their contacts, usually in the same relay and the coil side are the same symbols on the label, and the contact group number to show distinction. Relay contacts have three basic forms:
1 movable type (type H) coil is not energized when the two contacts are disconnected, power, the two contacts on the closure. The word phonetic prefix "H" said.
2 dynamic fault type (D type) coil is not energized when the two contacts are closed, the power of the two contacts on off. With the hyphenation of phonetic prefix "D" said.
3 conversion type (Z type) this is the contact type. A total of three contacts of the contact group, namely, the middle of the moving contact, the upper and lower each of a static contact. The coil is not energized, the movable contact and a static contact disconnect and another closed coil is energized, the movable contacts on the move, the original broken into closed, the original closed into a disconnected state, to achieve the purpose of conversion. Such a contact group is called a switching contact. With the "turn" the word phonetic prefix "Z" said.
Five, the choice of relay
1 understand the necessary conditions: first, the power supply voltage control circuit, can provide the maximum current; voltage and current control circuit; the control circuit needs a few groups, what type of contacts. When the relay is selected, the power supply voltage of the general control circuit can be used as the basis for selection. The control circuit should be able to provide adequate working current to the relay, or relay is not stable.
2 access to the relevant information to determine the conditions of use, you can find the relevant information, to identify the needs of the relay models and specifications. If the existing relay on hand, can be used to check whether the data can be used. Finally consider the size is appropriate.
3 pay attention to the volume of equipment. If used for general electrical appliances, in addition to considering the volume of the chassis, the small relay mainly consider the layout of the circuit board. For small appliances, such as toys, remote control devices should be used to select ultra small relay products.