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Description: the
image on the left shows the
basic operation of
the A/D. The
analog sensor-transmitter
converts the level signal
and generates a voltage
between 0
and 5 volts.
This analog signal enters
the 10-bit
converter. The
conversion result is given in
a decimal value between 0
and 1023 units. Using the 18F2550 Bolt system, which has up to 10 channels of A/D 10-bit resolution, a simple interface is built to generate a voltage of 0...5 volts through a precision potentiometer with 25 turns. This voltage enters Bolt system auxiliary port (pin 2) and later to pin RA5 (Channel 4) of 18F2550 microcontroller. Using special C18 library functions for the A/D converter, the program performs the conversion every half second to a decimal value between 0...1023, which is finally displayed on the LCD. |
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To
perform the test program,
an emulation of the
sensor-transmitter was done,
connecting a 10K
potentiometer, 25 turns, to the input (pin
2) of the auxiliary port
and later the
RA5 pin
(which corresponds
to channel 4 A/D
converter) of 18F2550.
Turning the potentiometer,
we can modify the output
voltage between 0-5
volts. Use
as a reference for
connections, the following diagram:
Ports and
connectors 18F2550
Bolt. In the table shown below the test programs are provided for this project, using functions in C18, library ADC-BOLT.h |
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A
test program was
developed, provided in
the table below.
Through the precision
potentiometer, you can control the
generated voltage from 0
to 5 volts and
therefore all the
decimal values range
from 0 to 1023. If you want to convert the value displayed on the LCD to engineering units, you can easily multiply the decimal value by a constant. Download here the C18 library specialized for the management of the A/D 18F2550 Bolt System: This library handles, initializes and reads the A/D, channel 4, of 18F2550 microcontroller. However, it can be easily modified for any other channel. |
TEST PROGRAM |
DESCRIPTION |
C18-BOLT-A-D-CONVERTER.c | Application using library ADC-BOLT.h |
C18-BOLT-A-D-CONVERTER.hex |