User manual

new program run and subtract the last counter reading that was
saved at the end of the program. The
delay(100)
at the end of the
program simulates a longer program runtime. Your program code
must be between // My program start and // My program end , to
determine the throughput time of your program code.
The first experiments and thus also the function test have hereby
been completed successfully. Leave the circuit set up as it is.
You will need it and expand it in the following experiments. In
the following chapters, you will learn a bit more about the
LC-display and its properties.
SETUP AND FUNCTION
OF THE LC-DISPLAYS
LCDs are used in many electronic devices, such as entertainment
electronics, measuring devices, mobile phones, digital clocks
and calculators. Head-up-Displays and video projectors also use
this technology. The following figure shows the LCD from the
learning package. This is a standard-5x8-dot-matrix-display
with 2 rows with 16 characters each.
An LCD generally consists of 2 individual glass panes and a special
liquid in between. The special characteristic of this liquid is
that it will turn the polarisation level of light. This effect is
influenced by applying an electrical field. The two glass plates
are therefore vaporised with a very thin metal layer each. To get
polarised light, a polarisation film is stuck to the upper glass
plate. This is called the polariser. Another such film must be
applied to the bottom glass plate, with its polarisation level
turned by 90°. This is the analyser.
In the resting condition, the liquid turns the polarisation level
of the incoming light by 90°, so that it can pass the analyser
unhindered. The LCD is thus transparent. Applying a specific
voltage to the vaporised metal layer now will cause the crystals
to turn in the liquid. This will turn the polarisation level of
the light by, e.g., another 90°: The analyser blocks out the
light; the LCD has become opaque.
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Polarisation in LC-displays does not mean polarity of the voltage
supply, but the gas, liquid and filter structure of the display.