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| Electronics Tutorial about Input and Output Devices |
Summary of Transducers |
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Summary of Transducers
Input Devices or Sensors
- Sensors are "Input" devices which convert one type of
energy or quantity into an electrical analog signal.
- The most common forms of sensors are those that detect Position, Temperature,
Light, Pressure and Velocity.
- The simplest of all input devices is the switch or pushbutton.
- Some sensors called "Self-generating" sensors generate output voltages or
currents relative to the quantity being measured, such as thermocouples and photo-voltaic solar cells and their output bandwidth equals
that of the quantity being measured.
- Some sensors called "Modulating" sensors change their physical properties,
such as inductance or resistance relative to the quantity being measured such as inductive sensors, LDR's and potentiometers and need to
be biased to provide an output voltage or current.
- Not all sensors produce a straight linear output and linearization circuitry
may be required.
- Signal conditioning may also be required to provide compatibility between the
sensors low output signal and the detection or amplification circuitry.
- Some form of amplification is generally required in order to produce a suitable
electrical signal which is capable of being measured.
- Instrumentation type Operational Amplifiers are ideal for signal processing and
conditioning of a sensors output signal.
Output Devices or Actuators
- "Output" devices are commonly called Actuators and the simplest
of all actuators is the lamp.
- Relays provide good separation of the low voltage electronic control signals and
the high power load circuits.
- Relays provide separation of DC and AC circuits (i.e. switching an AC current path
via a DC control signal or vice versa).
- Solid state relays have fast response, long life, no moving parts with no contact
arcing or bounce but require heatsinking.
- Solenoids are electromagnetic devices that are used mainly to open or close pneumatic
valves, security doors and robot type applications. They are inductive loads so a flywheel diode is required.
- Permanent magnet DC motors are cheaper and smaller than equivalent wound motors as
they have no field winding.
- Transistor switches can be used as simple ON/OFF unipolar controllers and pulse width
speed control is obtained by varying the duty cycle of the control signal.
- Bi-directional motor control can be achieved by connecting the motor inside a transistor
H-bridge.
- Stepper motors can be controlled directly using transistor switching techniques.
- The speed and position of a stepper motor can be accurately controlled using pulses so
can operate in an Open-loop mode.
- Microphones are input sound transducers that can detect acoustic waves either in the
Infra sound, Audible sound or Ultrasound range generated by a mechanical vibration.
- Loudspeakers, buzzers, horns and sounders are output devices and are used to produce
an output sound, note or alarm.
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