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First Lighthouse to use electricity is Statue of Liberty (1886)

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In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch. Automatically operated switches can be used to control the motions of machines, for example, to indicate that a garage door has reached its full open position or that a machine tool is in a position to accept another workpiece. Switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to automatically control a system.

There are a lot of types of switches. We will explain a few common used in microcontroller based systems.

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plllogoA tutorial or overview about the basic concepts of a phase locked loop, PLL, detailing how it works and how they may be designed.

The phase locked loop or PLL is a particularly flexible circuit building block. The phase locked loop, PLL can be used for a variety of radio frequency applications, and accordingly the PLL is found in many radio receivers as well as other pieces of equipment.


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A relay is an electromagnetically controlled on-off switch, used to isolate control electrical circuit from part of circuit that contains load. Current flows through the coil of the relay and creates a magnetic field which moves a lever and changes the switch contacts.

Relay                   relay                        

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Pulse Width Modulation (PWM) Tutorial



Pulse Width Modulation – Using digital pulses to create some analog value other than just ‘high’ and ‘low’ signal levels. Many digital systems are powered by a 5-Volt power supply, so if you filter a signal that has a 50% duty cycle you get an average voltage of 2.5 Volts. Other duty cycles produce any voltage in the range of 0 to 100% of the ‘high’ voltage, depending upon the PWM resolution.

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