Discussion on Analysis of Radiator of LED Bulb Light Plastic Case

Author: Mao Yu Hai

Recently, plastic radiators have also attracted people's attention. Materials with good thermal conductivity are usually materials with good electrical conductivity. In turn, plastics with poor electrical conductivity must have poor thermal conductivity. This is inevitable. So obviously metal is better than plastic. In fact, it is the same. So, isn't plastic used as a radiator? Not so!

Recently, a variety of thermal conductive plastics have been developed internationally, and most of the materials are based on engineering plastics and general-purpose plastics, such as PP, ABS, PC, PA, LCP, PPS, PEEK, and the like. The plastic is then filled with certain metal oxide powder, carbon, fiber or ceramic powder. For example, polyphenylene sulfide (PPS) can be mixed with large-particle magnesium oxide (40-325 mesh) to form an insulating heat-conductive plastic. Typical thermal conductivity ranges from 1-20 W/mK and some grades can reach 100 W/mK. This value is about 5-100 times that of traditional plastics. The thermal conductivity of general plastics is only 0.2 W/mK. However, if too much metal powder is added in order to obtain high thermal conductivity, it becomes conductive. It can not be applied in some occasions. The performance of some thermal conductive plastics from Coolploy in the United States is as follows.

E4505 (PC): Thermal Conductivity 10w/mk Thermal Conductive Applications: Enclosure and Radiator D5108 (PPS): Thermal Conductivity 10w/mk Thermal Insulation Application: Board/Chip D5506 (LCP): Thermal Conductivity 10w/mk Thermal Insulation Application: Board / Chip D8102 (TPE): Thermal Conductivity 3w/mk Thermal Insulation Application: Interface E5101 (PPS): Thermal Conductivity 20w/mk Thermal Conductive Applications: Radiator

So why can thermal plastics be made into heat sinks? Can its heat dissipation be compared to traditional aluminum radiators? Perfect, even better!

We know that any heat sink, in addition to being able to quickly transfer heat from the heat source to the surface of the heat sink, still relies on convection and radiation to dissipate heat into the air. The high thermal conductivity solves the problem of fast heat transfer, and the heat dissipation is mainly determined by the heat dissipation area, shape, natural convection and heat radiation, which are almost independent of the thermal conductivity of the material. So as long as there is a certain heat transfer capacity, the plastic radiator can still be a good radiator!

Generally speaking, if the distance from the heat source to the surface of the heat sink is less than 5 mm, as long as the thermal conductivity is greater than 5, the heat dissipation is dominated by convection, and at this time, conduction heat dissipation has no effect. This can be seen from the curve below.

Figure 1. Relationship between thermal conductivity and conduction convection heat dissipation

The relationship between thermal conductivity and conduction convection heat dissipation is given in Figure 1. In the figure, the abscissa is the thermal conductivity and the ordinate is the temperature difference between the heat source and the environment. The curves for the various colors are the distance between the heat source and the surface of the heat sink. If the distance is less than 5mm (green curve), as long as the thermal conductivity is greater than 5, its heat dissipation capacity is completely determined by convection. The smaller the temperature difference and the smaller the distance, the less important the thermal conductivity is.
And for an ideal good heat sink, about 70% of the heat is convective heat, and 30% of the heat is radiated by radiation.
The heat dissipation capability of the heat-conductive plastic is not inferior. Below are the thermal emissivity of various materials.

So it can be said that if two radiators of the same shape are identical, one is made of aluminum and the other is made of heat-conductive plastic. If the radiator made of aluminum is not blackened, its heat dissipation capability is not comparable to that of black thermal plastic. Into the radiator! Because the convection heat dissipation of the two is the same, and the radiation heat is better with plastic!

Take the example of a heat-dissipating plastic from Shanghai Hefu New Materials Co., Ltd. The specifications of this material are as follows:

Compared with commonly used aluminum heat sinks, there are other advantages to the plastic heat conductive material.

Compared with traditional materials, thermal conductive polymers have higher flexural and tensile stiffness, but have poor impact strength, and their inherent low coefficient of thermal expansion can effectively reduce part shrinkage.

In fact, it can be considered that its biggest advantage is insulation. Because of its good electrical conductivity, aluminum heatsinks are often a concern for non-isolated power supplies when they pass CE or UL certification. With plastic heat sinks, non-isolated power supplies can be used at the same time without worrying about safety issues.

In addition, its density is lighter than aluminum. The density of aluminum is 2700kg/m3, while the density of plastic is 1420 kg/m3, which is almost half of that of aluminum. Therefore, the heat sink of the same shape has a weight of only 1/2 of that of aluminum. Moreover, the processing is simple, and the molding cycle can be shortened by 20-50%, which reduces the pressure of cost.

The picture below shows an LED bulb made by a company in Shanghai using a heat-conducting plastic case radiator. It can dissipate about 8 watts of power. This power is already close to the ultimate power of the bulb (9W). If you want to further increase its power, you can only use forced air cooling.

LED bulb for plastic case radiator

The only drawback is that the plastic radiator monovalent expensive, it is not for a large LED to LED lights in the radiator such, only suitable for indoor low-power LED lamps.

 

WiFi 5 Wireless Router

First, Wireless Router
So what is a wireless router?

Wireless router, according to the definition of Baidu Encyclopedia: Wireless router is used for users to access the Internet, with wireless coverage of the router.

A wireless router can be thought of as a repeater that forwards the broadband network signal from the wall of your home through an antenna to nearby wireless network devices (laptops, Wifi-enabled phones, tablets, and all Wifi-enabled devices).

The popular wireless routers in the market generally support four access methods: dedicated xdsl/cable, dynamic xdsl, pptp, and generally can only support 15 to 20 devices online at the same time. It also has some other network management functions, such as dhcp service, nat firewall, mac address filtering, dynamic domain name and so on. The signal range of the general wireless router is 50 meters radius, and the signal range of some wireless routers has reached 300 meters radius.

The name of wireless router can be separated out of two keywords: wireless and routing.

Understand the technical principle behind these two words, you understand the wireless router.

Wireless is also what we often call Wi-Fi. Wireless routers can convert home broadband from wired to wireless signals, and all devices can happily surf the Internet as long as they connect to their own Wi-Fi. In addition, these devices also form a wireless local area network, where local data is exchanged at high speed and is not limited by the bandwidth of home broadband.

For example, many people have smart speakers in their homes that can be used to control various smart appliances. When you say small X small X, turn on the TV, the speaker actually finds the TV through the LAN and sends instructions, and does not need to connect to the Internet; And if you let it broadcast news, you have to get data through the Internet.

The Local Area Network we talked about earlier, also known as the Intranet, is represented by the Local Area Network (LAN) on the router, so the Wi-Fi signal is also called WLAN(Wireless LAN); The Internet we want to access, also known as the extranet, is represented on the router by the WAN(Wide Area Network).

On the Intranet, the IP address of each device is different, which is called a private address. All devices on the Internet share the same public address, which is assigned by broadband operators such as China Telecom Unicom.

The router is the bridge between the Intranet and the external network. The above mentioned IP address translation, packet forwarding, is the router routing function. In other words, the router is the hub of the home network, and the data of all the devices must be forwarded through it to access each other or reach the external network, which means that one husband is the key and ten thousand men are not open, so the comprehensive router is also called "home gateway".

Second, the demand for wireless routers
I do not know if there is a sudden WIFI break when you play games at home, and a stable router is crucial at this time. However, it is important to note that your WIFI frequently dropped may not be a problem with the router, it may also be a problem with the carrier network. (Router means I don't back this pot)

In fact, for most people, there are two basic requirements for wireless routers

Stable and do not drop
Fast Internet and easy setup
Some people will have some advanced needs:

There are some features, USB interface, can be external U disk or hard disk, can achieve simple nas functions, QOS, etc., to advertising and so on
Mesh networking, when the house area is large, multiple routers can be used for Mesh networking

How to choose a wireless router
The wireless router market is in the transition stage from WiFi 5 to WiFi 6, if you want to buy the first choice is definitely WiFi 6 wireless router, which is the future trend.

The speed of WiFi 6 is nearly 40% higher than the previous generation 802.11ac, and the highest connection speed can even reach 9.6Gbps, while the highest speed of 802.11ac is only 6.93Gbp. More importantly, unlike 802.11ac, which only covers the 5GHz band, WiFi 6 covers 2.4GHz and 5GHz. Although the 5GHz band has less interference, it has weak wall penetration ability, and the 2.4GHz band has strong wall penetration ability, which takes into account each other.

So why choose a WIFI6 router?

Compared with the previous generation of 802.11ac WiFi 5, the maximum transmission rate of WiFi 6 in the 5Ghz band has been increased from 3.5Gbps to 9.6Gbps, and the theoretical speed has been increased by nearly 3 times. WiFi 6's 5Ghz single-stream 80Mhz bandwidth can reach theoretical speeds of up to 1201Mbps and 160Mhz bandwidth of up to 2402Mbps.
The band supports 2.4Ghz and 5Ghz.
In terms of modulation mode, WiFi6 supports 1024-QAM, which is higher than the 256-QAM of WiFi 5, and the data capacity is higher. Some high-end WiFi 6 routers support 4096-QAM.
WiFi6 supports MU-MIMO (multi-user multiple-input multiple-output) technology, and supports both upstream and downstream MU-MIMO, with a maximum support of 8T×8R MU-MIMO. The speed is greatly improved. High concurrency, WiFi6 5GHz band, terminal connections up to 128! 5 times that of WiFi5. Effectively solve the Internet needs of multi-person networking and smart home;
WiFi6 adopts OFDMA (orthogonal frequency division multiple access) technology. After using OFDM to parent the channel, the transmission technology of transmitting data is loaded on the subcarrier, allowing different users to share the same channel, allowing more devices to access, with shorter response time and lower delay.
Low latency, WiFi6 time delay can be as low as 10ms, compared to WiFi5 30ms delay, only 1/3. This performance refresh is extremely friendly to game lovers;
If WiFi6 (wireless router) devices need to be certified by the WiFi Alliance, they must use the WPA 3 security protocol, which is more secure.
The WiFi6 wireless router is backward compatible with WiFi5 and WiFi4 terminals.

Fourth, the misunderstanding of purchasing routers
Is the through-wall router really through-wall?
Mistake; The country has strict limits on the transmission power of the wireless router antenna, if you have a lot of rooms in your home, and there are many walls between them, even if you buy an expensive wireless router, you can not do one to cover all the room signals. If the signal is not good, you can consider multiple wireless router Mesh networking.

Does a wireless router have a stronger signal with more antennas?
More antennas just to match the X*X MIMO mode, the more antennas, the more channels, can only ensure that the network is more stable, the impact on the signal is little, the strength of the signal is only related to the wireless transmission power. The wireless transmission power of the country has a standard.

Wifi 5 Wireless Router,5Gz Wifi Router,Wi-Fi Routers For The Home,Lte Modem Router

Shenzhen MovingComm Technology Co., Ltd. , https://www.movingcommiot.com