Information Technology Reference
In-Depth Information
Antenna
DIP switch
Antenna
Keyboard
Generating
and charging
device
Wireless
transmitter
Display
Wireless
receiver
PT2262
T
Amplifier
ADC
Printer
PT2272
Fig. 1. Temperature measure block diagram
Fig. 2. Temperature display and print block
It is composed of the power circuit, MCU, wireless receiver, recorder, key and dis-
play etc. its main function is receiving signal from temperature measuring device, and
save the temperature value in memorizer, and show and record the data. If received
the data exceed setup range, measurement device can also give an upper and lower
limit alarm. It includes four LED display, a micro-printer, four-setup keys, PT2272
and wireless receiving module. Passing the keys can set alarm temperature for upper
and lower limit.
2.3 The Temperature Measurement Wireless Communication Principle
The design uses wireless transceiver encoding/decoding chip set PT2262/2272. It is
Taiwan Princeton Technology Corp.'s low-power, wide voltage (2.6V-15V) universal
codec chip. It makes up of a wireless transmit/receive circuit matching with 315MHz
module. It is 18-pin package, mainly have address coding, receive/dispatch control
and the data input/output pin etc. Since only measure temperature, therefore, can use a
single wireless correspondence method. (Namely temperature measurement device
sends out data, display device receives data.)
Encoding signal sent out by PT2262 is composed of address code, data code and
synchronous code. Pin 14 (TE) is a code to start end of the data encoding for multi-
launch, low is effective, controlled by the MCU P1.0.Pin 17 (DOUT) is code exporta-
tion, output serial data signal. That MCU sends 4-bit data to PT2262 send to the wire-
less transmitter module through pin 17.During pin 17 is high 315 MHz high-
frequency transmitter starts oscillation and transmits high- frequency-amplitude sig-
nals. During pin 17 is low 315 MHz high-frequency oscillator to stop oscillation. So
high-frequency oscillator is completely controlled by pin17 output's digital signals of
PT2262, completes amplitude shift keying(ASK) modulation to make, is equivalent to
100% modulation of amplitude. When pin 14 is high, stop coding output, so that 3
I5MHz high-frequency oscillator do not work [2].
The data-received electric circuit is composed of PT2272 and 315MHz wireless re-
ceived module, PT2272 of pin14 (DIN) is serial data input, receive data signal come
from a wireless received module.pin17 (VT) is an output of the decoding effective
[3]. Usually low, decoding effectively translated into high. When PT2272 received
the signal, pin 17 become high after its address code checked twice is correct. At the
same time the corresponding four data output pin is also valid data. When AT89S52
queries that pin17 is high, receive data, and then save, show and print this data.
 
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