Type of time relay
I. classification according to working principle
According to its working principle, time relay can be divided into air damping time relay, electric time relay, electromagnetic time relay, electronic time relay, etc.
1. The air damping time relay uses the principle of damping when air passes through the small hole to obtain the time delay. Its structure consists of electromagnetic system, delay mechanism and contact. The electromagnetic mechanism is double port direct acting type, the contact system is micro switch, and the delay mechanism is air bag damper.
2. Electronic time relay
① electronic time relay is based on the principle that the capacitance voltage in RC circuit can't jump and can only gradually change according to the exponential law, that is, the electric damping characteristic can obtain the time delay.
② features: wide delay range, up to 3600s, high precision, about 5% in general, small volume, shock resistance and vibration resistance, convenient adjustment.
3. Motor type time relay
① the motor time relay uses the micro synchronous motor to drive the reduction gear system to obtain the time delay.
② features: wide delay range, up to 72 hours, delay accuracy up to 1%, and the delay value is not affected by voltage fluctuation and environmental temperature change.
③ the delay range and accuracy of motor time relay are incomparable to other time relays. Its disadvantages are complex structure, large volume, low service life and price responsibility. The accuracy is affected by power frequency.
4. Electromagnetic time relay. The electromagnetic time relay is made of the principle that the armature of the magnetic system is released after the electromagnetic coil is cut off and the magnetic flux is slowly attenuated. The characteristic of the electromagnetic time relay is that the contact capacity is large, so the control capacity is large, but the delay time range is small and the accuracy is slightly poor. It is mainly used in the control of the DC circuit.
II. Classification by delay mode
According to different delay modes, time relay can be divided into two types: on delay type and off delay type.
1. Power on delay time relay starts to delay immediately after receiving the input signal, and its executive part outputs the signal to operate the control circuit only after the delay is completed; when the input signal disappears, the relay immediately returns to the state before the action.
2. The power-off delay time relay is the opposite. When the input signal is obtained, the executive part has an output signal immediately; but after the input signal disappears, the relay needs to go through a certain delay to recover to the state before the action.
Function of time relay
Time relay is widely used in remote control, communication, automatic control and other electronic equipment, and is one of the most important control elements. Time relay mainly includes air damping type, electric type and electronic type. At present, the commonly used time relay is a large-scale integrated time relay. Time relay is also widely used in production equipment. It can accurately grasp the time scale and improve the accuracy and performance of products.
Main features of time relay
1. The principle of the electric time relay is similar to that of the clock. It is driven by the internal motor to rotate the reduction gear to obtain the time delay. This relay has high delay precision and wide delay range (0.4 ~ 72h), but its structure is complex and its price is very expensive.
2. Transistor time relay is also called electronic time relay. It uses delay circuit to delay. This kind of relay has high precision and small volume.
3. Air damping time relay, also known as air bag time relay, delays according to the resistance generated by air compression. It has simple structure, low price, large delay range (0.4 ~ 180s), but low delay accuracy.
4. The delay time of electromagnetic time relay is short (0.3 ~ 1.6s), but its structure is relatively simple, and it is usually used in power-off delay occasions and DC circuits.
Precautions for use of time relay
1. Keep the time relay clean, otherwise the error will increase;
2. Check whether the power supply voltage and frequency are consistent with the voltage and frequency of the time relay before use;
3. Select the control time of time relay according to the user's requirements;
4. Pay attention to wiring according to the circuit diagram for DC products, and pay attention to the polarity of power supply;
5. Try to avoid the use in places with obvious vibration, direct sunlight, humidity and oil contact.