Motors & Fans & Heat Sink:
Characteristics of DC micro motor:
1. The efficiency of micro DC motor is generally higher than that of other types of motors, so the volume of DC motor is generally small to achieve the same output power. When the installation position is limited, the micro DC motor is relatively suitable.
2. One feature of micro DC motor is that the motor can automatically slow down according to the load to achieve great starting torque. This is more difficult for AC motors. In addition, DC motor is easy to absorb the sudden change of load size, and the motor speed can automatically adapt to the load size.
Types of DC micro motors
It can be divided into special motor, electromagnetic motor and permanent magnet motor. Special motors generally have no windings and the drive is more complex. As a kind of motor, it has its own system. Electromagnetic motors have different characteristics due to different excitation modes. The performance of permanent magnet motor is similar to that of electromagnetic shunt motor, with large starting torque and hard mechanical characteristics. The speed changes little when the load changes. It is suitable for low-power DC drive, such as electric toys, electric tools, audio equipment, automobile electrical appliances, etc. This paper mainly discusses the drive of this kind of micro DC motor with small power, low voltage and small volume.
The motor has only two leads. The speed can be adjusted by adjusting the supply voltage or current. The polarity of the two leads can be changed and the motor can be reversed. Its driving circuit is controlled by single chip microcomputer. Generally, it is required to drive forward and reverse rotation and speed regulation, and the volume should not be too large.
How to judge the performance of cooling fan？
When we buy a cooling fan, people who know it generally know that we can choose from its bearings, specifications, number of blades and other main parameters. Then, how to judge its performance? Today, let's get to know with the engineers of FBelec!
Oil bearing and ball bearing are widely used in it. Generally, the price of oil bearing is low and the rotation noise is low. Some manufacturers add polytetrafluoroethylene to the oil bearing to make the oil bearing have the characteristics of ball bearing. However, the noise of fan using ball bearing is higher than that of oil bearing and the price is higher than that of oil bearing, but its advantage is high reliability and long service life.
Generally, the length of the fan blade and the large total heat dissipation area of a large heat dissipation fan are the embodiment of its performance, so its total air flow is very large. If the design scheme is not good, the heat dissipation capacity of the large fan will not be as good as that of the small fan.
Blades also have a great impact on its performance. If other parts of the same fan remain unchanged and only 5 blades are replaced with 7 blades, the change of exhaust volume is not easy to improve. However, from the perspective of fan speed, the speed of 7 blades is smaller than that of 5 blades. Relatively speaking, if 7 blades are selected, there will be less oil leakage and longer service life.
Heat dissipation method of PCB circuit board of electronic products:(heatsink)
When the electronic equipment works, it will generate certain heat, so that the internal temperature of the equipment will rise rapidly. If the heat is not dissipated in time and continues to rise, the device will fail due to overheating and the reliability of the electronic equipment will decline. Therefore, it is very important to do a good heat dissipation treatment for PCB.
1. PCB heat dissipation
PCB self heat dissipation is a simple, practical and low-cost heat dissipation method. At present, PCB circuit boards are mainly copper-clad / epoxy glass cloth substrate or phenolic resin glass cloth substrate. Although these substrates have excellent electrical and processing properties, they have poor heat dissipation, and it is almost impossible to expect heat conduction by the resin of PCB itself. Therefore, it is necessary to design heat dissipation from the surface of the element to the surrounding air.
So how? The best way is to improve the heat dissipation capacity of the PCB in direct contact with the heating element and transmit or emit it through the PCB. For example, adding heat dissipation copper foil, using large-area power supply ground copper foil, heating vias, exposing copper on the back of IC chip, reducing the thermal resistance between copper sheet and air, etc.
2. Optimize component layout
Devices on a PCB printed board shall be arranged in zones according to their calorific value and heat dissipation degree as far as possible. Devices with small calorific value or poor heat resistance (such as small signal transistors, small-scale integrated circuits, electrolytic capacitors, etc.) shall be placed at the uppermost flow (inlet) of the cooling air flow, Devices with high calorific value or good heat resistance (such as power transistors, large-scale integrated circuits, etc.) are placed at the downstream of the cooling air flow. Avoid the concentration of hot spots on the PCB, distribute the power evenly on the PCB as much as possible, and maintain the uniformity and consistency of PCB surface temperature performance.
The heat dissipation of printed boards in the equipment mainly depends on air flow, so the air flow path should be studied in the design, and the devices or printed circuit boards should be configured reasonably.
