The working principle and characteristics of the relay
The relay is an electronic control device, it has a control system (also known as the input circuit) and the control system (also known as the output circuit), usually used in the automatic control circuit, it is actually less current to control than the high current of an “automatic switch”. Therefore, in the circuit plays automatically adjust to the role of security, conversion circuit.
Working principle and characteristics of an electromagnetic relay
Electromagnetic relays are generally composed by the core, coil, armature, contacts reed. As long as both ends of the coil plus the voltage coil will flow current, resulting in the electromagnetic effect, the armature will be attracted to the role of the electromagnetic force to overcome the spring tension to return suction to the core, so as to drive the armature moving contact and static contact (normally open contact) pull. When the coil power, the electromagnetic suction disappeared, the armature will return to its original position in the spring reaction force, so that the dynamic contact with the stationary contact (normally closed contact) pull. This pull, release, so as to achieve conduction in the circuit, the purpose of cutting off. Relay normally open, normally closed “contact, can be distinguished: static contact, the relay coil is not energized in a disconnected state known as” normally open contact “; is connected to the state of the static contact The point is called the “normally closed contact”.
2, thermal dry reed relay working principle and characteristics of
The new thermal switch thermal reed relay is a thermal magnetic material detection and control of temperature. It consists of temperature, magnetic ring, constant ring, dry reed pipe, thermal installation piece, composed of plastic substrates, and some other attachments. Thermal reed relay without coil excitation generated by the permanent magnetic ring magnetic drive switching. The constant ring whether the reed switch magnetic force is determined by the temperature control characteristics of the thermal ring.
The working principle and characteristics of the 3, the solid-state relay (SSR)
The solid state relay is a two-terminal input, the other two terminals for the output of the four-terminal device, the middle of the isolation device input and output electrical isolation.
Solid state relay load type of power can be divided into AC and DC-type. Normally open and normally closed switch types can be divided into. Isolation type can be divided into the type of hybrid, transformer isolated and optically isolated, to a maximum of optical isolation. .
Second, the relay technical parameters of the main products
1, rated working voltage
Refers to the relay coil voltage. Depending on the relay model, the AC voltage can also be a DC voltage.
2, the DC resistance
Refers to the DC resistance of the relay coil, through the multimeter, measure.
3, pull-in current
Refers to the relay to produce the minimum current to pull the action. During normal use, given the current must be slightly larger than the pull-in current, so that relay to stabilize the work. The coil in the increase of operating voltage, usually not more than 1.5 times the rated working voltage, otherwise it will produce a larger current to the coil burnt.
4, the release of the current
Refers to the relay release action of the maximum current. When the relay state current decreases to a certain extent, the relay will revert to the unpowered release state. When the current is far less than the pull-in current.
5, the contact switch voltage and current
Refers to the relay allows the load voltage and current. It determines the relay can control the size of the voltage and current use can not exceed this value, it will easily damage the relay contacts.
Third, the relay test
1, the measured contact resistance
Multimeter, the resistance profile measurement normally closed contact with the fixed points of resistance, the resistance should be 0; normally open contact with the fixed point of resistance to infinity. It can distinguish that is normally closed contact, that is normally open contact.
2, the measured coil resistance
The multimeter R × 10Ω file available to measure the resistance of the relay coil, the coil in order to determine whether there is open circuit.
3, measuring the pull-in voltage and pull-in current
Got the adjustable power supply and ammeter, and a set of voltage input to the relay, and the string into the ammeter to monitor the power supply circuit. Slowly increase the power supply voltage, I heard the sound of relay, write down the pull-in voltage and pull-in current. For the sake of accurate, can try a few times and averaged.
4, measuring the release voltage and current release
Is also a connection test as described above, when the relay pull, and then gradually reduce the supply voltage, when the hear the relay from happening again to release the sound, write down the voltage and current can also try a few times obtained The average release voltage and the current release. Under normal circumstances, the release voltage of the relay is about the pull-in voltage of 10 ~ 50%, if the release voltage is too small (less than 1/10 of the pull-in voltage), you can not normally use, so will the stability of the circuit pose a threat, the work is not reliable.
Four relay electrical symbols and contacts in the form
The relay coil in the circuit using a long box symbol indicates that if the relay has two coils, draw two parallel long box. Relay in a rectangular box or long box next to the subscript text the symbol “J”. Relay contacts, there are two representations: one is to draw them directly on one side of the rectangular frame, this notation is more intuitive. The other is in accordance with the circuit to connect the needs of the various contacts were drawn to the respective control circuit, usually marked on the same text symbol next to the same relay contacts and coil, and the contact group numbered to show the difference. The relay contacts are three basic forms:
(1) the dynamic co-type (H type) when the coil is not energized two contacts are disconnected after the power, the two contacts closed. To the co-word phonetic prefix “H”.
Move off type (D type) when the coil is not energized two contacts are closed, energized two contacts on the disconnect. Said hyphenation Pinyin prefix “D”.
(3) the conversion type (Z type) contact group type. This contact group a total of three contacts, namely the middle of the moving contact, upper and lower stationary contact. Coil not energized, the moving contact and one static contact is open and another closed, the coil is energized, the moving contact on the move, so that the original disconnected closed original closed into a disconnected state, to achieve the conversion purpose. This contact group referred to as changeover contact. Using the “transfer” of the phonetic prefix “z”.
The selection of five relay
One to understand the necessary conditions: ① control circuit power supply voltage can provide the maximum current; ② control circuit voltages and currents; ③ charged circuit group, and what form of contact. Selection of the relay, general control circuit power supply voltage can be used as an optional basis. The control circuit should give the relay to provide sufficient current, or the relay is unstable.
(2) access to such information to determine the conditions of use, you can find relevant information to identify the type and specifications of the relay number. On hand, relays, based on data matching can use. Finally, consider the appropriateness of size.
Note that the volume of the apparatus. If used for general electrical appliances, in addition to considering the chassis volume, small relays to consider the circuit board mounting layout. For small appliances, such as toys, remote control device should be used ultra-small relay products.
This article from the Consumer Electronics