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Write a short note on: Relay, Stepper motor, UART, RS-232

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1.Relay:
It is an electro mechanical device.
It acts as dynamic path selector for signals and power.
It contains a relay coil made up of insulator wire on a metal core and metal armature with one or more contacts

 2.Stepper motor:
A stepper motor is a widely used device that translates electrical pulses into mechanical movement.
In applications such as disk drives, dot- matrix printers, robots etc. the stepper motor is used for possible control. 
Stepper motor rotates in fixed steps of a certain number degrees. The step size can vary from 0.60 to 900.

 3.UART:
For Universal Asynchronous Receiver Transmitter is one of the most used serial protocols. It's almost as old as I am, and very simple. Most controllers have a hardware UART on board.

 4.RS-232:
It is a very simple serial protocol that was originally used for modems and teletypes. It is what is commonly called a serial port (or a COM port in MS-Windows).

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