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How to Use 555 Timer to Operate the Bulb in the Specified Time

How to use 555 timer IC in the circuit to keep the bulb (lamp) on for several minutes and then return to its off state.

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Some Skills for RFID Circuit Board Design

Although there are many uncertainties in the theory of RF circuit board design, there are still many rules that can be followed in RF circuit board design. However, in the actual design, the real practical skill is how to compromise these rules when they cannot be implemented due to various limitations. This paper will focus on various issues related to RF circuit board partition design.

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Radio Circuit Using Powerless Transistors

Several transistor radios described in this article do not require battery power. They use high-frequency signals that are transmitted to the air by radio stations, and are rectified to obtain DC power, which is used as a power source for the radio. However, this kind of radio can only receive broadcasts of local close-range high-power radio stations; in addition, it must also use an outdoor antenna and a good ground wire; the earphone should use a coil impedance of not less than 2 kΩ.

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Metal Detector Circuit

You can see the presence of metal detectors in many public places such as airports and theaters. They are often for safety reasons to detect if someone is carrying a metal object that does not conform to the regulations. In this project we will design a simple metal detector circuit. There are many kinds of circuits for metal detectors, but most of them are more complicated, so here we use 555 timer to design a simple metal detector circuit.

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LED Constant Current Power Supply Circuit Diagram

LED The lamp power supply adopts the constant current drive mode, that is, the output current is constant, and the output voltage changes with the load change. In the case of measurement, the measured voltage value is the 310V DC voltage after AC 220V rectification.

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