chapt9 - ME 4204 Mechatronic Systems Lesson Objectives...

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1 Interfacing 2 2008/09 Semester 1 Lecture 8 ME 4204 Mechatronic Systems 2 Lesson Objectives ± Interfacing with controllers ± Noise Filtering 3 Introduction ± When a controller is used to control a system, it has to accept input signal, respond to it and produce an output signal for the required control action. ± Input and output devices are connected to a controller system (PC, microcontroller, etc.) through ports . ± Once the input or output signal is ready for transmission, there are several modes can be used: ± Parallel mode ± Serial mode ± 1- or 2-way direction Interface Controller ( Microcontroller, PC, etc.) Sensors Actuators 4 Serial vs Parallel Transmission Mode ± Parallel mode means multiple bits move in parallel down a multiple pathway or bus from source to destination. ± Serial mode means the bits move one at a time, in a series, down a single pathway. ± Parallel mode traffic is faster in that multiple bits are moving together but the number of pathways is a limiting factor. For this reason, parallel mode is usually used for components located close to one another while serial mode is used if any distance is involved. Serial Mode Parallel Mode
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5 Interfacing Relays ± Relays are devices which allow low power circuits to switch a relatively high Current/Voltage ON/OFF. For a relay to operate, a suitable pull-in & holding current should be passed through its coil. Generally relay coils are designed to operate from a particular voltage often its 5V or 12V. The transistor is driven into saturation (turned ON) when a LOGIC 1 is written on the PORT PIN thus turning ON the relay. The relay is turned OFF by writing LOGIC 0 on the port pin. ± A diode (1N4007/1N4148) is connected across the relay coil, this is done so as to protect the transistor from damage due to the BACK EMF generated in the relay's inductive coil when the transistor is turned OFF.When the transistor is switched OFF the energy stored in the inductor is dissipated through the diode & the internal resistance of the relay coil. The transistor is driven into saturation (turned ON) when a LOGIC 1 is written on the PORT PIN thus turning ON the relay. The relay is turned OFF by writing LOGIC 0 on the port pin. A diode (1N4007/1N4148) is connected across the relay coil, this is done so as to protect the transistor from damage due to the BACK EMF generated in the relay's inductive coil when the transistor is turned OFF.When the transistor is switched OFF the energy stored in the inductor is dissipated through the diode & the internal resistance of the relay coil. Controller Driver IC/ Transistor Relay High current source 6 Interfacing Solenoids ± When a controller or PC interface is used to drive a solenoid, one of the outputs of the controller or interface board has to be amplified in order to control the operation. The mode of operation is simply ON/OFF.
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This note was uploaded on 01/16/2010 for the course ENG 91301 taught by Professor Lui during the Spring '08 term at Hong Kong Institute of Vocational Education.

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chapt9 - ME 4204 Mechatronic Systems Lesson Objectives...

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