Operation: They typically use an electrical signal to vibrate a
diaphragm or produce an oscillating sound wave. The frequency and
amplitude of the sound can be varied to create different types of alerts.
Operation: They use light sources like LEDs or incandescent bulbs,
often with flashing mechanisms to increase visibility. The color of the
light is often standardized to indicate specific types of warnings (e.g.,
red for danger).
3. Tactile Warning Devices (Vibrators):
These Devices produce a physical vibration.
Operation: These devices use small motors with unbalanced weights
to create vibrations. These are useful for people with hearing
impairments or in noisy environments.
These devices provide written or visual information.
Operation: They use displays like LCD screens or indicator panels to
present messages or symbols. These are common in control systems
and complex machinery.
Sender Units Used in Warning and Monitoring Circuits
Sender units are responsible for detecting abnormal conditions and triggering the
appropriate warning devices. Here are some common types:
1. Sensor-Based Sender Units:
These units use sensors to detect changes in physical parameters.
Types:
Temperature Sensors: Detect changes in temperature and
trigger alarms if it exceeds or falls below a set threshold.
Pressure Sensors: Monitor pressure levels and trigger alarms if
they become too high or too low.
Smoke Detectors: Detect smoke particles in the air and trigger
fire alarms.
Motion Sensors: Detect movement and trigger security alarms.
Fluid Level Sensors: Detect high or low fluid levels in tanks or
other containers.
Operation: The sensor converts the physical parameter into an
electrical signal, which is then processed by the sender unit. If the
signal indicates an abnormal condition, the sender unit activates the
warning device.
2. Manual Sender Units:
These units are activated manually by a person.
Types:
Emergency Stop Buttons: Immediately shut down machinery
or systems in case of an emergency.
Fire Alarm Pull Stations: Manually trigger fire alarms.
Panic Buttons: Trigger security alarms in case of an
emergency.
Operation: When the button or switch is activated, it closes or opens
an electrical circuit, which then triggers the warning device.
3. Control System Sender Units:
These units are integrated into larger control systems.
Operation: They monitor various parameters and trigger warnings
based on programmed logic. These are common in industrial
automation and building management systems.
Example: a PLC (Programmable Logic Controller) that monitors
multiple sensor inputs, and if a certain combination of inputs occur, it
then sends a signal to a warning light, and a siren.
Electronic Displays: Construction and Operation
1. LED (Light-Emitting Diode)
Construction:
An LED is a semiconductor diode that emits light when an
electric current flows through it.
It consists of a p-n junction made of semiconductor material
(e.g., gallium arsenide phosphide).
When forward-biased, electrons and holes recombine at the
junction, releasing energy in the form of photons (light).
The color of the light depends on the semiconductor material
used.
Operation:
When a voltage is applied across the p-n junction, electrons
move from the n-type to the p-type region, and holes move in
the opposite direction.
At the junction, electrons and holes recombine, releasing energy
as light.
The intensity of the light is proportional to the current flowing
through the LED.
LEDs are energy-efficient, have a long lifespan, and are
available in various colors.
2. Cathode Ray Tube (CRT)
Construction:
A CRT is a vacuum tube containing an electron gun and a
phosphor-coated screen.
The electron gun emits a beam of electrons, which are deflected
by electromagnetic fields.
The electron beam strikes the phosphor screen, causing it to
emit light.
Operation:
The electron gun fires a beam of electrons towards the screen.
Deflection coils or plates control the direction of the electron
beam, allowing it to scan across the screen.
The intensity of the electron beam determines the brightness of
the light emitted from the phosphor.
CRTs were widely used in televisions and computer monitors
but have been largely replaced by flat-panel displays.
3. LCD (Liquid Crystal Display)
Construction:
An LCD consists of liquid crystal material sandwiched between
two glass plates.
Polarizing filters and electrodes are used to control the
orientation of the liquid crystal molecules.
A backlight is often used to illuminate the display.
Operation:
When an electric field is applied, the liquid crystal molecules
align, changing the polarization of light passing through them.
By controlling the electric field, individual pixels can be turned on
or off, creating images.
LCDs are used in a wide range of devices, including laptops,
smartphones, and televisions.
4. Vacuum Florescent Display (VFD)
Construction:
A VFD is a vacuum tube containing a cathode, grid, and anode
(phosphor-coated).
Electrons emitted from the cathode are accelerated towards the
anode by the grid.
When electrons strike the phosphor, it emits light.
Operation:
The cathode emits electrons, which are controlled by the grid.
The electrons strike the phosphor-coated anode, causing it to
glow.
VFDs are bright and have a wide viewing angle, making them
suitable for applications like car stereos and industrial displays.
5. DC EL (Direct Current Electroluminescent)
Construction:
DC EL displays consist of a phosphor layer sandwiched
between two electrodes.
A dielectric layer is often used to improve performance.
The phosphor is excited when a DC voltage is applied.
Operation:
When a DC voltage is applied, the phosphor layer emits light
through the process of electroluminescence.
These displays are known for their thin profile, and relatively
uniform light emmission.
These displays are less common than other display
technologies.
Driver Information Systems:
1. Vehicle Conditioning Monitoring
Operation:
This system monitors various vehicle parameters to ensure
optimal performance and prevent potential problems.
Sensors throughout the vehicle collect data on:
Engine temperature
Oil pressure and level
Tire pressure
Battery voltage
Fluid levels (coolant, washer fluid)
Brake pad wear
A central control unit processes the sensor data and displays
warnings or alerts on the instrument cluster or a dedicated
display.
Warnings can be visual (indicator lights) or audible (chimes,
beeps).
Modern systems may also provide detailed diagnostic
information and maintenance reminders.
Purpose:
To alert the driver to potential problems before they become
serious.
To optimize vehicle performance and fuel efficiency.
To enhance safety.
2. Trip Computer
Operation:
A trip computer calculates and displays various trip-related data.
It uses data from vehicle sensors, such as speed, fuel level, and
engine load, to calculate:
Average fuel consumption
Instantaneous fuel consumption
Distance traveled
Time elapsed
Average speed
Range (distance to empty)
The data is typically displayed on the instrument cluster or a
dedicated display.
The system resets with a button press, or after a specific
amount of time has passed.
Purpose:
To provide drivers with real-time information about their driving
habits and fuel efficiency.
To help drivers plan their trips and manage fuel consumption.
3. Global Positioning System (GPS)
Operation:
GPS uses a network of satellites to determine the vehicle's
precise location.
GPS receivers in the vehicle receive signals from multiple
satellites.
By calculating the time it takes for the signals to reach the
receiver, the system can determine the vehicle's latitude,
longitude, and altitude.
GPS data is used for:
Navigation: Providing turn-by-turn directions.
Location tracking: Monitoring vehicle location.
Mapping: Displaying maps and points of interest.
Modern systems combine GPS with mapping software and real
time traffic data to provide accurate and up-to-date navigation.
