smt electronic components are the basis of electronic products, electronic components are the general term for electronic components and electronic devices
The common electronic components of SMT are: resistors, capacitors, resistors, capacitors, inductors, diodes, transistors, IC sockets, and fuses.
Common SMT polar component identification methodsPolar components need special attention during the entire PCBA processing process, because directional component errors can cause mass accidents and failure of the entire PCBA board, so it is extremely important for engineers and production personnel to understand SMT polar components.
1. Polarity definitionPolarity means that the positive and negative poles or the first pin of the component and the positive and negative poles or the first pin on the PCB (printed circuit board) are in the same direction. If the component does not match the direction on the PCB, it is called Bad reverse.
2. Polarity recognition method1. Resistor has no polarity
2. Capacitor
2.1 Ceramic capacitors have no polarity
2.2 Tantalum capacitors have polarity. PCB board and device positive label: 1) ribbon label; 2) "+" sign; 3) bevel label.
2.3 Aluminum electrolytic capacitors have polarity. Part marking: ribbon for negative; PCB marking: ribbon or "+" for positive.
3. Inductor
3.1 Two solder-end packages such as chip coils have no polarity requirements
3.2 Multi-pin inductors have polarity requirements. Part mark: Dot/"1" represents the polarity point; PCB board mark: Dot/circle/"*" represents the polarity point.
4. Light Emitting Diode
4.1 SMT surface mount LEDs have polarity. Part negative label: green is negative; PCB negative label: 1) vertical bar represents, 2) ribbon represents, 3) silk screen sharp corner represents; 4) silk screen "匚" box represents.
5. Diode
5.1 SMT surface mount two-terminal diodes have polarity. Part negative marking: 1) ribbon, 2) groove, 3) color marking (glass body); PCB negative marking: 1) vertical bar marking, 2) ribbon marking, 3) silk screen sharp corner marking, 4) "匚" Box mark
6. Integrated Circuit (Integrated Circuit)
6.1 SOIC type package has polarity. Polarity indication: 1) ribbon, 2) symbols, 3) pits, grooves, 4) hypotenuse
6.2 SOP or QFP type packages have polarity. Polarity indication: 1) pit/groove indication, 2) one of the points is different from the other two/three points (size/shape).
6.3 QFN type package has polarity. Polarity marking: 1) One point is different from the other two points (size/shape), 2) Hypotenuse marking, 3) Symbol marking (bar/"+" sign/dot).
7. Ball Grid Array (Ball Grid Array)
7.1 Part polarity: pit/groove marking/dot/circle marking; PCB board polarity: circle/dot/letter "1 or A"/bevel marking. The part polarity point corresponds to the polarity point on the PCB.
smt resistance identification methodThe color of the color ring resistance generally has 12 colors: brown, red, orange, yellow, green, blue, purple, gray, white, black, gold, and silver. The first ten colors represent 1-9 (black represents 0 ), gold and silver represent two errors (plus or minus 5% and plus or minus 10%)
There are four color circles on the resistors that are normally shipped from the factory. The first two colors represent pure numbers. For example, orange and black represent the number 30 (not that the resistance is 30 ohms), and the third color circle represents the number of 0, for example On the third day, if the color ring is red, it means that there are two 0s behind the number 30, and the resistance of this resistor is 30,000 ohms (3k ohms)
The color of the last color ring is either gold or silver. For example, if the last color ring is silver, it means that the resistance of the changed resistor is hovering between plus or minus 10% of 3000 ohms (the real resistance of the resistor is within this range) Any certain value
Capacitors are mainly divided into electrolytic capacitors and element capacitors. The shape of the electrolytic capacitor is a cylinder, and its capacitance is marked on its cylindrical surface, and it has polarity (the long leg is the positive electrode, and the short leg is the negative electrode)
On the other hand, the chip capacitor has no polarity. Its shape is generally a round pie with three numbers marked on it. The first two digits represent the capacitance value, and the third digit represents the number of zeros, such as 233, which means The capacitance value is 23 000PF or 0.023 microfarad
Incremental Encoder is commonly used, and Absolute Encoder is used if there are strict requirements on position and zero position. Servo system should be analyzed in detail, depending on the application situation. Commonly used incremental encoder for speed measurement, which can be used for infinite accumulation measurement; Absolute encoder is used for position measurement, and the position is unique (single or multiple turns). Finally, it depends on the application situation and the purpose and requirements to be realized.
Incremental Linear Encoders,Linear Optical Encoder,Linear Position Encoder,Encoder Bearing Tester
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