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
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.
Forms of Signal Degradation
Simple Interfacing for Digital Signals
Switch Debouncing Switch debouncing happens when mechanical contacts switch and thus from the force of the switching they bounce for a few milliseconds.
Actual switch Bounce Signal
Hardware Methods for Debouncing
Software method of Debouncing 1
Software method of Debouncing 2
Interfacing Keypads 1
Interfacing Keypads 2
Keypad Scanning Algorithm
Optical Devices: Single 7-segment Display
Optical Devices: Multiplexed 7-segment Display
Optical Devices: Example Circuit
Optical Devices: Opto-Isolator
Object Sensors
Shaft Encoders Angular Speed S = output frequency / number of holes revolutions per second This setup does not give indication of direction
Incremental Quadrature Shaft Encoder
Absolute Shaft Encoders
Inductive Load Switching
Examples of Inductive Loads
Mechanical Relays
The use of H-Bridge 1
The use of H-Bridge 2
The use of H-Bridge 3
The use of H-Bridge 4
Semiconductor H-Bridge 1
Semiconductor H-Bridge 2