【 Weak current College 】 relay standard 】

<br> <br> Relay works and characteristics <br> <br> Relay is an electronic controller, it has a control system (also known as the input circuit) and control system (also known as the output circuit), generally apply to .automatic control circuit, it actually is a small current to control large currents in an "auto-switch". It plays in the circuit of automatic regulation, security protection, conversion circuits, etc. <br> <br> Electromagnetism relay works and characteristics .<br> <br> Electromagnetic relays General core, coil, armature, contact Reed, etc. As long as the coil ends with a certain voltage, coil will flow through a certain amount of current to produce electromagnetic effects, keeper in the role of .electromagnetic force attract return spring under tension ceiling to core, thus driving the keeper of the contact points of contact and static (normally open contact). When the solenoid coil is powered by suction or disappear, the keeper of the spring returns to its original location .in reaction to enable dynamic contact with original static contacts (normally closed contact). This suction, discharge, thus achieved in the circuit of conduction, and cutting purposes. For relay "normally open, normally closed contacts, you can do" to distinguish between .: relay coil is not powered on, is in a disconnected state of static contact, known as "normally open contacts"; in a connected state for static contact called "normally closed contact." <br> <br> Thermal dry Reed relay works .and characteristics <br> <br> Thermal dry Reed relay is a thermosensitive magnetic materials testing and control of the temperature of the thermal switch. It consists of temperature magnetic ring, constant magnetic ring, Reed pipe, duct mounting plate, plastic substrates and other .accessories. Thermal Reed relay without coil excitation, and the constant magnetic ring produces magnetic drive switch action. Permanent magnetic ring can offer to do a Reed pipe temperature sensor magnetic is a magnetic ring of temperature characteristics. <br> <br> Solid state relay .(SSR) works and characteristics <br> <br> Solid state relay is a two terminal as the input and the other two terminals for output of 4-terminal devices, Middle isolation device input and output of electrical isolation. <br> <br .> Solid state relay press load power supply types can be divided into AC-and DC-type. Press the switch type can be divided into normally open and normally closed. According to the quarantine type can be divided into hybrid, transformer isolated and photoelectric isolation .type to photoelectric isolation type for most. <br> <br> <br> The main technical parameters of relay <br> <br> Rated working voltage <br> <br> Refers to the relay coil Typ desired voltage. According to the .model, the relay can be AC voltage or DC voltage. <br> <br> DC resistance <br> <br> Refers to the relay coil of DC resistance, through the universal table measurements. <br> <br> Pull-in .-current <br> <br> Refers to the relays can produce the smallest suction action. In normal use, given current must be slightly larger than the pull-in current so that relay to stable work. For coil the working voltage, generally do .not exceed the rated voltage of 1.5 times, otherwise it will produce a larger current and coil burn. <br> <br> Release current <br> <br> Refers to generating release action relay maximum current. When the status of current pick- .up decreases to a certain extent, the relay will return to the powered release status. When the current far less than closing current. <br> <br> Contact switch the voltage and current <br> <br> Refers to relay allows load voltage .and current. It determines the relays to control the size of the voltage and current, and must not exceed this value, otherwise it is very easy to damage the contacts of relays. <br> <br> Relay test <br> <br> .Contact resistance measurement <br> <br> Universal table of resistance, measuring close regular contact and fixed point resistance, its resistance value should be 0 and normally open contact and fixed points of resistance to infinity. It can thus be distinguished from that is normally .closed contact that is normally open contact. <br> <br> Measuring coil resistance <br> <br> Available universal table R × 10 Ω stall resistance measuring relays coils to determine the existence of an open coil. <br> <br> .Measuring pull-in voltage and current pick-up <br> <br> Find a adjustable voltage and current meter, to enter a set voltage relays, and power supply circuit conspiracy into the ammeter. Slowly increase the power supply voltage, hear the sound .of the pick-up, note the pull-in pull-in voltage and current. For the sake of accuracy, you can try several times and averages. <br> <br> Measurement of voltage and current release release <br> <br .> It is like the above then connection test, when the relay event of pick-up, and gradually reduce the supply voltage, when hear the relay again when you release the voice, write down the voltage and current, but also try to acquire more .than a few times on average release voltage and current release. In General, the relay release voltage of about pull-in voltage 10 ~ 50%, if you release the voltage is too small (less than 1 / 10 of pull-in voltage) ., you cannot normally use, this will pose a threat to the stability of the circuit, is not reliable. <br> <br> Relay of symbols and contact form <br> <br> Relay coil circuit with a long box notation, if .relay has two coils, draw two long boxes side by side. At the same time in a long box or long box next to the marked text symbols of relay "J". Relay contacts have two methods: one to draw them directly in the long .side of the box, this notation is more intuitive. Another way is to follow the circuit connection, the contact points are drawn to the respective control circuit, usually in the same relay contacts and coils respectively noted on the same text symbols, and the number .of contact group, to distinguish the two. Relay contacts there are three basic forms: <br> <br> Movable hop type (h) coil not powered two-contact is broken, powered, two-contactIt closed. To close the word Ruby .-prefix "H". <br> <br> Fixed broken type (d type) coil not power on when two contacts are closed, after power disconnect two contacts. Using hyphenation of Ruby-prefix "D". <br> <br .> Conversion-type (Z)-this is the contact group. The contact group has a total of three contact points, ie the middle is moving up and down all the contacts, the contacts of a static. Coil not power on when moving contacts .and one of the static contact disconnect and another closed, coil energized, dynamic contact is moved so that the original broken into closed, the original closed into the off State, reach the purpose of the conversion. This contact group called convert contacts. Use the ."go" in the words of Ruby-prefix "z" represents. <br> <br> Relay selection <br> <br> 1. to understand the necessary condition: ① power voltage control circuit, and can provide maximum current; ② .is control circuit voltage and current; ③ charged circuit takes several groups, what forms of contact. Choose relay, general control circuits power supply voltage can be used as the basis for selection. Control circuit should be able to relay to provide adequate operating current, .otherwise the pick-up is unstable. <br> <br> 2. access to the relevant information to determine the conditions of use, you can find relevant information, identify the needs of the model and specifications of relay. If you already have on .hand, which narrows the data relay check whether you can use. Finally, consider the size is appropriate. <br> <br> 3. takes note of the volume of the apparatus. If it is used for General Electric, apart from the chassis .volume, small relay circuit mounted a major consideration. For small appliances, such as toys, remote control unit you should use the product mini relay. <br> <br>.