Interfacing to External Devices
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Transcript of Interfacing to External Devices
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Interfacing to External Devices
Explore Digital Interfaces techniques Introduce some complex optical devices and how to interface them Describe methods for switching devices on and off
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Interfacing Digital Input Signals
General requirements of all digital input signals: The voltage input level should only be the
legal allowed voltage. They should not be corrupted by glitches They should switch cleanly and fast.
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Forms of Signal Degradation
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Simple Interfacing for Digital Signals
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Switch Debouncing Switch debouncing happens when
mechanical contacts switch and thus from the force of the switching they bounce for a few milliseconds.
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Actual switch Bounce Signal
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Hardware Methods for Debouncing
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Software method of Debouncing 1
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Software method of Debouncing 2
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Interfacing Keypads 1
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Interfacing Keypads 2
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Keypad Scanning Algorithm
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Optical Devices: Single 7-segment Display
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Optical Devices: Multiplexed 7-segment Display
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Optical Devices: Example Circuit
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Optical Devices: Opto-Isolator
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Object Sensors
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Shaft Encoders
Angular Speed S = output frequency / number of holes
revolutions per second
This setup does not give indication of direction
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Incremental Quadrature Shaft Encoder
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Absolute Shaft Encoders
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Inductive Load Switching
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Examples of Inductive Loads
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Mechanical Relays
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The use of H-Bridge 1
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The use of H-Bridge 2
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The use of H-Bridge 3
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The use of H-Bridge 4
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Semiconductor H-Bridge 1
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Semiconductor H-Bridge 2
http://www.dprg.org/tutorials/1998-04a/