0 Preface
This article refers to the address: http://
With the growth of China's national economy, the amount of road traffic has increased significantly, and the speed of driving has also increased significantly. It has been followed that traffic accidents are on the rise. Airbags are a very effective measure to reduce casualties.
1 Main features of MMA2204D
The most characteristic change in a car collision is acceleration. Therefore, airbag design generally detects acceleration based on acceleration changes generated during a car collision. Accelerometers are commonly used in testing. Accelerometers used in airbags should generally have the following properties:
â—‡ should be able to convert the acceleration generated by a car collision into an electrical signal proportional to it (such as current, voltage, etc.), and the sensitivity is high:
应 There should be a certain amplification and frequency selection capability for the induced electrical signal:
â—‡ should have self-test function:
â—‡ should have good temperature stability, high entanglement, firm structure and small size. Easy to install;
â—‡In order to reduce the cost of airbags, the price of accelerometers should be as low as possible.
2 Accelerometer chip selection
There are many types of devices that can be used as accelerometers. In recent years. Due to the rapid development of electronic technology and integrated technology, the performance of micromachined silicon piezoresistive accelerometers and silicon capacitor accelerometers has been improved day by day, and the price has been reduced to an acceptable level. According to the performance of the acceleration used by the airbag, this paper chooses Freescale's silicon capacitor micromechanical accelerometer MMA2204D. This is a silicon capacitive accelerometer with integrated signal amplification, signal processing, low pass filtering and compensation. The device's zero-acceleration bias, full-scale range, and filtering characteristics are all set by the manufacturing unit, eliminating the need for external passive components. Figure 1 shows the functional block diagram of its internal simplified structure.
3 MMA2204D's main functions
Freescale's MMA2204D accelerometer is a surface micromechanical integrated circuit accelerometer. The chip contains a surface micromechanical capacitance measuring unit (g-cell) and a CMOS single adjustment application type ASIC, wherein the g-cell is a semiconductor mechanical structure. The MMA2204D accelerometer has a polycrystalline silicon inertia block inside. It is suspended between two fixed polycrystalline poles. The acceleration acts to move the inertia block, causing the capacitance to change, and then converting the capacitance into a voltage output. To avoid mechanical shock, the accelerometer is also equipped with a damping and over-range braking mechanism. In addition, the MMA2204D features filtering, self-test and status output.
3.1 Filtering
The MMA2204D automotive airbag accelerometer contains a four-pole switched-capacitor filter that uses the Bessel filter because it has a time-continuous response function. Therefore, a pulse-like integral can be saved. Because the filter uses switched-capacitor technology, there is no need for additional missing components (resistors and capacitors) to set the lower cutoff frequency.
3.2 Self-test
The sensors in the MMA2204D pass the self-test feature to verify the mechanical and electrical integrity of the accelerometer at any time after installation, a feature that is critical to automated airbag systems. For the car, the integrity of its system must be ensured. MMA2204D uses the fourth board as the self-checking board in g-celI, and the s-out est pin is active high, so the electrostatic force generated by it can cause the offset of the intermediate board, and the accelerometer can control the ASIC to measure This deviation produces a relative proportional output voltage. This process ensures the function of the mechanical and electronic parts of the accelerometer.
3.3 Status
The MMA2204D accelerometer contains fault detection and fault latches whose status pins can output status signals from the fault latch and the self-test. Whenever one or more of the following conditions occur, its status pin will output a high level:
(1) The supply voltage is lower than the voltage threshold for low voltage detection;
(2) The clock frequency is lower than the lowest frequency of the clock detector;
(3) The parity of the EPROM is an odd number.
4 MMA2201 main performance parameters and application circuit
The main performance parameters of MMA2204D are listed in Table 1. The hardware design circuit based on MMA2204D automotive airbag system is shown in Figure 2.
5 Conclusion
The MMA2204D-based automotive airbag circuit is simple in design, large in measurement range, high in sensitivity, and low in temperature and frequency. In addition, the MMA2204D chip also comes with self-test circuit, and the price is moderate, which can fully meet the design requirements of the airbag accelerometer.
With spiralling energy costs accompanying the constant need to replace bulbs and tubes our 2 ranges of Marine Aquarium Lighting makes perfect sense.A conservative savings in electricity consumption of up to 50% can be achieved over metal halides and 25% onT5 Fluorescents.
2 Manual dimmers for White, Blue change the intensity of lighting
Simulates the sunset and sunrise
55pcs 3w leds offer lighting to tank effectively
Adjustable kits, detachable cords
Philizon Lighting is dedicated to provide high quality and durable lighting product for customer with very competitive price.Our products mainly foucs on LED Grow Lights and LED Aquarium Light .The equipment and materials to produce Hydroponics Led Grow Light and marine Aquarium Led Light fixture imported from Taiwan, Japan, Korea and Unites States, such as automatic SMT machine, reflowsoldering machine,all kinds of electric test equipment, large integrating sphere and such sorts of productionand R&D equipment.
Item Display
Key Features
1.The lifespan is over 50000 hours,low maintenance costs.
2.Energy conservation,saving over 80% energy than the traditional HPS.
3.High light efficiency,90% of the light will be absorbed by the aquatic plants,while just 8%-10% to the HPS.
4.Build-in cooling system,could solve the heat dissipation excellently.
5.Built-in power supply, CE approved, No setup required, just simpler and safer plugs directly into AC85V-264V, no reflector & ballast needed.
Package Include
1 X Led Aquarium Light
1 X Free Hanging Kit
1X Free Power Cord
All the lamps have passed strict quality examination and are packed carefully before shipping.In order that our customers get high quality lamps,we attach importance to every details.
Application
1. coral reef lighting,fish tank lighting,coral reef tank lighting
2. Aquarium Lighting ,aquarium art,aquarium shop,aquarim centre
3. fish bowl lighting,fish lighting,freshwater lighting,saltwater lighting
Our Led Plant Grow Light and led aquarium lamp are popular in led market,cause its elegant outlook and its high quality and competitive price.We are eager to kick off cooperation with you, our valuable customers. Let`s work together and save the energy.
Warmly welcome to visit Philizon in Shenzhen China.
Marine Aquarium Lighting
Marine Aquarium Lighting,Marine Led Aquarium Lighting,Marine Led Lighting,Marine Aquarium Led Lighting
Shenzhen Phlizon Technology Co.,Ltd. , https://www.philizon.com