Relay, understand in, thank you. Relay switching circuits

First of all, you should distinguish what is weak current and what is strong current, they are relative, not simply refer to the level of voltage. Because the important role of relay is twofold: one is isolation, that is, the isolation of the control circuit and the controlled circuit; The second is to use small signals to control high-power signals.

The relay is actually a combination of an electromagnet and a switch, the electromagnet has a rated voltage, under normal circumstances, the work of the relay will be unreliable when it is lower than the rated voltage, and the electromagnetic coil will be burned when it is higher than the rated voltage.

His main parameters: driving voltage, generally commonly used volts; Load capacity: Expressed in amps, relays range from milliamps to thousands of amps. Then there is the number of switch contacts.

Relays have rated voltage levels, and you can buy as many volts as the output voltage of your controller. Consider the voltage level, current size, temperature range, and so on.

There are many kinds of relays, the volume is large and small, the contact capacity is from 1A to tens of A, and the coil voltage is from a few volts to hundreds of volts, which should be selected according to your actual needs.

First of all, you measure the coil voltage of the relay or the output voltage, secondly, a 24V control voltage relay, when the voltage rises to 24 * 70% and starts to act, 30% * 24V is released, so even if you use the voltage of 220 to go up as long as the coil does not burn him is also the action can be released, the problem is that if the 24VDC control voltage of the relay, then you go to 220VDC or 220VAC then the relay coil must be unbearable. It also does not achieve the effect of controlling the opening and closing time.

Summary. First: Determine the approximate scope of the fault.

First of all, use a multimeter to measure whether the power supply voltage of the control line is normal, and generally the actual voltage is less than 85% of the rated voltage. If the voltage of the control line is normal, then the possible cause is a line problem or a contactor problem.

Then test whether the voltage of the contactor coil is normal, and the actual voltage of the same shall not be less than 85% of the rated voltage. If the voltage at both ends of the coil is normal, there is a problem with the contactor. If there is no voltage at both ends of the coil, there is a problem with the control line.

Second: find the point of failure.

1.If the power supply is out of power, then check whether the upper power supply has power coming over; Check whether the fuse is burned;

2.If it is a problem with the contactor, then replace the contactor; In addition, look at whether the surface of the coil is burnt and whether there is an abnormal smell to judge whether the coil is burned; In the case of power failure, it is also possible to judge whether the contactor coil is burned out by measuring the resistance (normally there is a certain resistance, and the burnout resistance should be infinite); Check whether the contactor armature is stuck or corroded, etc.

Relay switching circuits

Hello. Hello, what is this for?

Now the problem is that the coil does not suck and, may I ask the problem may appear in**well as the solution in**.

If the jujube and electrical appliances do not suck, it is necessary to check whether its coil is normal, because the coil has a corresponding resistance value. At this time, you can use a rock guess multimeter to measure, if the resistance value is relatively large or 0 in this case, it means that the coil has been damaged, and at this time it is necessary to replace the slag trace with a new relay to use.

If it is very difficult, it means that there are foreign objects in the coil, and the shell of the relay should be removed to remove the foreign objects when the stove is chaotic, and then test it after the cleaning is completed. If it is not able to suck in, it is necessary to see if the spring blade is deformed, and if so, it needs to be corrected.

In addition to the relay, there are other parts of the circuit that can be problematic.

First: to judge the approximate range of the fault, first use a multimeter to measure whether the power supply voltage of the control line is normal, and the actual voltage is generally lower than 85% of the rated voltage can not be properly sucked up. If the voltage of the control line is normal, then the reason may be a line problem or a contactor problem.

Then test whether the voltage of the contactor coil is normal, and the actual voltage of the same shall not be less than 85% of the rated voltage. If the voltage at both ends of the coil is normal, there is a problem with the contactor. If there is no voltage at both ends of the coil, there is a problem with the control line.

Second: Find the fault point 1If the power supply is out of power, then check whether the superior power supply has power coming over; Check whether the fuse is burned; 2.

If it is a question of the contactor, then replace the contactor; In addition, look at whether the surface of the coil is burnt and whether there is an abnormal smell to judge whether the coil is burned; In the case of power failure, it is also possible to judge whether the contactor coil is burned out by measuring the resistance (normally there is a certain resistance, and the burnout resistance should be infinite); Check whether the contactor armature is stuck or corroded, etc.

Relay is an electronic control device, it has a control system (also known as an input loop) and a controlled system (also known as an output loop), usually used in automatic control circuits, it is actually a kind of control with a smaller current to control a larger current"Sell with automatic switch".Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit. Relay is an automatic control device that changes by leaps and bounds when the input quantity (electrical, magnetic, sound, light, heat, also known as excitation) reaches a certain value.

The input signal x of the relay continuously increases from zero to the action value xx when the armature starts to engage, and the output signal of the relay immediately jumps from y=0 to y=ym, that is, the normally open and open contact is turned on from the break. Once the tentacle is closed, the input x continues to increase, and the output signal y will no longer change. When the input amount x drops from a value greater than xx to xf, the relay begins to release and the normally open contact is disconnected.

We call this characteristic of the relay the relay the relay characteristic, also known as the input-output characteristic of the relay.

The relay circuit is simply a circuit with a relay, so if you understand the relay, you will know the role of this circuit and its application.

The relay circuit is a control conversion circuit in the control circuit. For example, the intermediate relay used in the middle of the control circuit to convert the middle of the car at the same time, there is also a time relay device that converts in the form of a time difference so that a certain point is not converted at the same time. They are an indispensable part of complex control circuits.

The relay output is generally a strong current controlled by a weak current. This is the saying in circuit control.

In many automation equipment, the circuit ultimately needs to control some actuators (such as motors, electromagnets), and the control of these actuators can be carried out through relays, bidirectional thyristors, transistors and other switching devices, so there are corresponding types such as "relay output, bidirectional thyristor output, transistor output" for the output end of the circuit.

In fact, it is very simple, the ordinary relay is equivalent to a single-pole double-throw switch, there are three pins to control the external circuit, when the control current is not passed (the default state) the middle pin is connected to a left pin, and the middle pin is connected to the right pin when the control current is passed, the suction of the relay is to act on the electromagnet with current, because the current is not small, so the IO port of the single-chip microcomputer alone is not enough to make the relay engaged, a drive should be added (play the role of power amplification, provide enough current to the relay), and then the single-chip microcomputer with I 0 port to control the drive, and then the drive circuit (driver chip such as UM2003) outputs enough current to make the relay engage, that's it.