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Distributed
Temperature Sensor
introduction
1.1 Temperature sensor background
In the human living environment,
temperature playing an extremely important
role
。
No matter where you
live, engaged in any work, ever-present
dealt with temperature under. Since the 18th
century, industry
since the industrial
revolution to whether can master send exhibition
has the absolute temperature touch.
In
metallurgy, steel, petrochemical, cement, glass,
medicine industry and so on, can say almost eighty
percent of industrial departments have
to consider the factors with temperature.
Temperature for industrial
so
important, thus promoting the development of the
temperature sensor.
1.2
Temperature sensor development
Major
general
through
three
sensor
development
phase:
analog
integrated
temperature
sensor.
The
sensor is taken with
silicon semiconductor integrated workmanship,
therefore also called silicon sensor or
monolithic integrated temperature
sensor. Such sensing instruments have single
function (only measuring
temperature),
temperature
measurement
error
is
smaller,
price
low,
fast
response,
the
transmission
distance,
small
volume,
micro-consumption
electronic
etc,
suitable
for
long
distance
measurement
temperature,
temperature
control,
do
not
need
to
undertake
nonlinear
calibration,
peripheral
circuit
is
simple. It is currently
the most common application at home and abroad, an
integrated sensor
。
Typical
products
have
AD590
AD592,
TMP17,
LM135,
g
integrated
temperature
controller.
Analog
integrated temperature controller
mainly include temperature control switch,
programmable temperature
controller, a
typical product have LM56, AD22105 and MAX6509.
Some increase strength type integrated
temperature controller (for example
TC652/653) also contains the A/D converter and
cure good sequence,
this process with
the intelligent temperature sensor some
similarities. But it is not its system, work by
micro
processing device control, this
is the main difference between. Intelligent
temperature sensor. intelligent
temperature
sensor
(also
called
digital
temperature
degrees
sensor)
is
in
the
mid
1990s
launch.
It
is
microelectronics technology, computer
technology and the dynamic testing technology
(ATE) crystallization.
Intelligent
temperature
sensor
internal
contain
temperature
sensor,
A/D
converter,
signal
processor,
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页
memory (or
registers) and interface circuit. Some products
still take multiplexer, central control system
device (CPU), random access memory
(RAM) and read only memory (ROM). Intelligent
temperature sensor
is
characteristic
of
temperature
data
and
relevant
can
output
the
temperature
control
of
the
quantity,
adaptation various micro controller
(MCU);
1.3 Single point and more
temperature sensor
The
development
trend
of
the
temperature
sensor.
In
the
21st
century,
the
temperature
sensor
is
headed in high precision,
multi-function, bus, standardization, high
reliability and safety, development of
virtual sensor and network sensor,
research monolithic temperature measuring system
and other high-tech
direction develop
rapidly. Sensors in the application temperature
controlling system. Current market exists
mainly
single
point
and
more
two
temperature
measurement.
For
single
point
temperature
foundment
instrument, mainly adopts
the traditional analog integrated
temperature
sensor,
which
heat
resistance,
thermocouple
sensors measuring accuracy, high measurement
range, and got the general application. This
product
is
temperature
measuring
range
℃
~
200
mostly
between
800
℃
,
resolution
12th,
and
least
distinguishable temperature in 0.001 ~
0.01 between. Cabin LED display module, shows
ranging from 4 to
16. Some instruments
also has memory function, can store several
hundred to a few thousand sets of data.
This instrument can be very good meet a
single user single-point measurement needs. More
temperature
measurement,
relative
and
single
point
measurement
precision
has
certain
gap,
although
realized
the
multi-channel
temperature measurement and control, but the price
is expensive. In view of the present
market
situation,
proposed
this
topic
can
satisfy
requirements,
scalable
and
cost-effective
single-chip
multi-channel
temperature measuring system. Through the first
temperature sensor DS18B20 acquisition,
and then through the C51 SCM processing
and displayed on the digital tube, can be
collected indoor or a
greenhouse around
in different locations of the temperature, with
four digital tube to display. The first
digital pipe display acquisition is
which way, which channel. Three digital pipe
display after the acquisition
channel
by temperature, accurate to 0.1 degrees.
2. The system realized and
related technologies
system is
realized
By
the
whole
control
system
for
core
AT89C51,
using
four
ways
of
temperature
sensor
DS18B20
in
production
site
for
distribution
area
of
four
different
temperature
measurement
result
with
the
chip
checking, collation store and display,
and through the button control, temperature will
process after the
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页
LED digital display to come out, and
the software assurance system anti-interference
capacity
。
four DS1820
connected
to
MCU
respectively,
this
scheme
four
IO
mouth
occupy
MCU
four
IO
though,
but
the
microcontroller
IO
mouth
under
the
condition
of
mouth
not
shortage
by
this
scheme
greatly
simplify
programming
difficulty,
shorten
the
design
cycle,
also
can
guarantee
the
stability
of
the
system.
A
multipoint connection as shown
“
1-1
”
DS1820
DS1820
DS1820
DS1820
AT89C51
MCU
P1.0
P1.1
P1.2
P1.3
Display element
Button control unit
1-1 multipoint connection
2.2 .AT89C51 Chip introduction
AT89C51 is a 4K bytes FLASH Memory
(Erasable Programmable and FPEROM - FLASH for the
campaigns
with) low voltage, high-
performance CMOS eight microprocessors, commonly
known as the microcontroller.
AT89C2051
is a 2K bytes with flash memory can be erased
programmable read-only memory , SCM can
erase
read-only
memory
can
be
repeated
erased
1000
times.
This
device
adopts
ATMEL
high-density
non-volatile
memory
manufacturing
technology
manufacturing,
and
industrial
standard
MCS
-
51
instruction set and output tube
compatible. Due to the multifunctional 8 bits CPU
and will be flashing on
single chip
combination of memory, ATMEL AT89C51 is a kind of
high efficient micro controller, AT89C2051
is a streamlined version. AT89C
51microcontroller as many embedded control system
.Arrange appearance
and pin as shown in
figure
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页
1-2
AT89C51 pins figure
Major
features:
·
and MCS - 51 compatible
·
4K bytes
programmable FLASH memory
·
life: 1000 write/wipe cycle
·
data retention
time: 10 years
·
the static job: 0Hz - 24MHz
·
level 3 program
memory lock
·
128
x 8 bits internal RAM
·
32 programmable I/O lines
·
two 16 timer
·
5 interrupt
source
·
programmable serial channels
·
low power
consumption of idle and power lost mode
·
piece inside
oscillator and clock circuit
Tube feet explains:
VCC:
power supply voltage.
GND: grounded.
P0 Mouth:
P0
mouth a eight leak level two-way I/O mouth open,
every foot can absorb
8TTL gate
current. When the pipe mouth P0 feet
first write 1, defined as high resistance input.
P0 can be used for
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页
external program data storage, it can
be defined as the eighth data/address. In FIASH
programming, P0
mouth as the source-
code input port, when FIASH check, the source-code
P0 output, when P0 external
must be
pulled.
P1 mouth: mouth is an internal
P1 provide pull-up resistors 8-bit two-way I/O
mouth, P1 mouth buffer
can receive 4TTL
gate current output. P1 mouth tube feet, was then
write 1 for high, pull up inside can be
used as input, P1 mouth be external
pull down for low electricity at ordinary times,
will output current, this
is due to
internal pull
up sake. In FLASH
programming
and calibration, P1 mouth
as eighth address to
receive.
P2 mouth: for an internal P2 mouth on
the 8-bit pull-up resistors two-way I/O port, P2
mouth to receive,
the
output
buffer
4
TTL
gate
current,
when
P2
mouth
is
written
its
tube
feet
are
internal
pull-up
resistors, and push
as input. And so as the input, P2 mouth feet are
external down tube, will output current.
This is due to internal pull up sake.
P2 mouth when used external program memory or 16
address external
data memory access, P2
mouth high output address eight. In a given
address
external 8 address advantage,
when for reading and writing data memory, P2 when
the special function
registers
mouth output
of
content. P2 mouth in FLASH programming
and
the calibration eight
address
when receiving high
signal and control signals.
P3 mouth:
P3 mouth pipe is 8 feet with internal pull-up
resistors two-way I/O port, may receive four TTL
gate current out put. When P3 mouth
writing
input, due to external drop-
down for low level, P3 mouth will output current
(ILL) this is due to pull up's
sake.
RST: reset input. When oscillator reset
device to keep RST feet high level two machine
cycle time.
ALE/PROG: when access
external storage, address latch allows the output
level of the position for latch
address
byte. During the FLASH programming, this pin for
input programming pulse. In peacetime, the ALE
with a constant frequency cycle output
is the pulse signal, the frequencies of the 1/6
oscillator frequency.
So it can be used
against external output pulse or used for timing
purpose. However it is: whenever used
for external data storage, will skip a
ALE pulse. If you want to ban the ALE output can
be in SFR8EH address
for 0. At this
time, only by performing the ALE MOVX, MOVC
instruction is ALE to take effect. In addition,
the pins were slightly up. If
microprocessor in external execution ALE, buy a
ban is invalid.
/ PSEN: external
program memory choice of communication number. By
external program memory in
during
the
instruction
fetch,
each
machine
cycle
twice
/PSEN
effective.
But
on
a
visit
to
external
data
storage, the two effective/PSEN signals
will not appear.
/
EA/VPP:
when/EA
keep
low
levels
in
this
period,
the
external
program
memory
(0000H
-
FFFFH),
whether have
internal program memory. Note encryption method 1,
/ EA will RESET for internal focus;
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页
When/EA end
keep high electricity at ordinary times, internal
program memory here. During the FLASH
programming, this pin is also used VPP
12V programming power (on).
XTAL1: the
inverting oscillator amplifier input and input to
the internal clock operating circuit.
XTAL2: from reverse oscillator output.
18B20 Chip introduction
DALLAS
latest
digital
temperature
sensor
DS18B20
profile
new
devices
smaller,
wider
and
voltage
applied to the DALLAS semiconductor company more
economic DS1820 digital temperature sensor
is the world the first piece of support
economic characteristics, the user can
easily form sensor network for measuring system,
the construction
of a new concept
introduction. DS18B20
also support
°
C ~ + 125
°
C, in - 10 ~
+ 85
°
C range, precision
°
C for + 0.5.
Scene in
can greatly improve the system
of anti-jamming.
Suitable for the scene
in the bad environment temperature measurement,
such as: environment control,
equipment
or process control, temperature measurement of
consumer electronics, etc. And the previous
generation product is different, the
new product support 3V ~ 5.5 V voltage range, make
the system design
more flexibly and
conveniently. But a new generation of products
cheaper, smaller. DS18B20 can program
sets 9 ~ 12 resolution, precision
°
C for + 0.5.
Optional smaller encapsulation way, more wide
voltage
range. Resolution setting, and
users set alarm temperature EEPROM, stored in
power lost and still save.
DS18B20
performance is the best product of new generation!
Performance to price also is very good!
DS18B20 New performance:
(1)
data available supply, voltage range: 3.0 ~ 5.5 V;
(2) temperature measuring range: - 55
℃
~ + 125 in - 10
~ + 85
℃
to + 0.5
℃
when precision;
(3)
programmable
resolution
for
the
9
~
12,
the
corresponding
can
distinguish
respectively
℃
,
the
temperature of 0.5
℃
and 0.125
℃
, by 0.25 0.0625
℃
;
(4) 12
resolution in most 750ms temperature into digital
within;
(5) negative pressure
characteristics: power at the polarity,
thermometers won't because when heating
and burned, but can't work normally.
DS18B20 Appearance and internal
structure:
DS18B20 internal structure consists
mainly of four parts: 64-bit photolithography ROM,
temperature
sensors,
nonvolatile
temperature
alarm
triggers
TH
TL,
configuration
and
registers.
DS18B20
tube
feet
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页
arrangement is
“
1-3
”,
internal structure is
“
1-4
”
1-3 DS18B20 tube feet arrangement
(1) DQ for digital signal
input/output terminal;
(2) GND for
power;
(3) VDD for external power
supplies input (in parasitic power connection mode
grounding).
1-4 internal
structure
3. Debug simulation
s
Proteus is Labeenter
electronics company research UK EDA software.
Proteus is not only the analog and
digital
circuit,
d/a
hybrid
circuit
design
and
simulation
platform,
but
also
is
currently
the
world's
most
advanced, the most complete various
types of micro controller system design and
simulation platform. It
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