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Digital Electronics: Principles, Devices and Applications

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Microcontrollers 593V CCV CCMicrocontrollerI/O PinLEDGND(a)V CCMicrocontrollerI/O PinLEDGND(b)Figure 14.25Interfacing LEDs to a microcontroller.microcontroller as shown in Fig.14.25(b). The LED in this case glows when the microcontroller pin isset HIGH.14.6.2 Interfacing Electromechanical RelaysFigure 14.26 shows the typical connection diagram for interfacing an electromechanical relay to amicrocontroller. The NPN transistor is used to provide the desired current to the relay coil as themicrocontroller cannot drive the relay directly. The freewheeling diode is required as the current

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