During the component selection process, you will see resistance with zero resistance. Then the question is! Since the resistance is zero, is it also called resistance? If the resistance is approximately zero, that is the wire. If the resistance is equal to 0, this is a superconductor! Then let's briefly introduce the use of zero-ohm resistors. 1. Single-point grounding for analog and digital ground All the grounds will eventually be connected together and merged into a ground plane before entering the ground. If it is not connected together, it is a "floating ground" and there is a pressure difference, and it is easy to accumulate charge and cause static electricity. Ground reference 0 potential, all voltages are reference ground, the ground standards must be consistent, so all kinds of ground should be short together. People think that the earth can absorb all the electric charges and always maintain stability. It is the final reference point. Although some boards are not connected to the earth, the power plant is connected to the earth. The power on the board will eventually return to the power plant. If analog ground and digital ground are directly connected, mutual interference will result. Not short and bad, generally we will use these four methods to solve this problem. 1 With magnetic beads, the equivalent circuit of the magnetic beads is equivalent to a band-stop filter, which only significantly suppresses the noise of a certain frequency point. It is necessary to estimate the noise frequency in advance in order to select the appropriate model. In the case of uncertain or unpredictable frequencies, the beads do not fit. 2 with a capacitor connection, the capacitor is easy to cross, resulting in floating ground. 3 Inductor connection; bulky inductors occupy space in high-density integrated boards, with many spurious parameters and instability, and high-speed PCBs are prone to EMI. 4 Connected with a 0 ohm resistor. A 0 ohm resistor is equivalent to a very narrow current path, which effectively limits the loop current and suppresses noise. The resistance has attenuation in all frequency bands (0 ohm resistor also has impedance), which is stronger than magnetic beads. 2. Use in the circuit 1 There is no function in the circuit, only on the PCB for debugging convenience or compatible design. 2 can be used for jumpers, if a section of the line is not used, directly without the resistor can be (does not affect the appearance). 3 When the matching circuit parameters are uncertain, it is replaced by 0 ohm. When the actual debugging, the parameters are determined, and then replaced by the specific numerical components. 4 When measuring the current consumption of a part of the circuit, you can remove the 0 ohm resistor and connect it to an ammeter. This is convenient for current consumption measurement. 5 When wiring, if the actual fabric does not pass, a 0 ohm resistor can also be added. 6 acts as an inductor or capacitor under high frequency signals. (Related to external circuit characteristics) Inductors are used to solve EMC problems. Like ground and ground, between power supply and ICPin 7 Single-point grounding (protected grounding, working grounding, and DC grounding are separated from each other on the equipment and each becomes an independent system.) 8 fuse function 9 When used in current bridges, the signal path is broken when the electrical ground plane is divided. At this time, the signal loop must be bypassed to form a large loop area, and the influence of the electric field and magnetic field becomes stronger. Easily interfere / be disturbed. A 0 ohm resistor across the partition provides a short return path and reduces interference. 10 Configure the circuit. In general, jumpers and dip switches should not appear on the product. Sometimes the user will tamper with the settings, which can easily lead to misunderstandings. In order to reduce maintenance costs, 0 ohm resistors are used instead of jumpers, etc., soldered to the board. The vacant jumper is equivalent to an antenna at high frequencies, and the patch resistor has a good effect. 3. Use of wiring Interconnections during wiring, debugging/testing, temporary replacement of other chip devices, and temperature compensation devices are often required for EMC measures. In addition, the 0 ohm resistance is smaller than the parasitic inductance of the via hole, and the via hole will also affect the ground plane (because you want to dig the hole), and there are different size 0 ohm resistors allowed to pass the current different, generally 0603 1A, 0805 2A, So different currents will use different sizes. In addition, when magnetic beads and inductors are used to reserve positions, they must be packaged according to the size of magnetic beads and inductors. Therefore, different sizes such as 0603 and 0805 are available. Usually 0805 package 0 resistance, current should be normal within 2A. Normal electronic devices have an upper limit current, mainly because the actual device has some resistance, not an ideal 0 resistance, and heat must be controlled. Similar to 0 resistance is the wire. Piezo Buzzer,Dc Electro Magnetic Buzzer,Buzzer Acoustic Components,Piezo Buzzer For Thermometer Jiangsu Huawha Electronices Co.,Ltd , https://www.hnbuzzer.com
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