Tuesday, January 11, 2011

【 Weak current College 】 of microprocessor temperature control system 】

Abstract: the SCM is of small size, versatile, low cost, wide application, etc., can be said, intelligent control and automation center around one single chip. Currently, a study and application of the single climax in the rise of mass to the whole society. Learn the most effective method of the microcontroller is the theory and practice, this article using a microcontroller made 80C51 temperature control system that highlights the system hardware architecture and programming methods.
Keywords: monolithic integrated circuit, temperature sensor, die/number converter
«Ò» ¡ ¢ temperature control system composition and working principle
In industrial production and daily life, to the requirements of temperature control system, the main is to guarantee the temperature at a certain temperature range, good stability, not oscillating, system speed requirements. The following simple analysis of the microprocessor temperature control system design and implementation. Scene temperature after sampling by temperature sensor for analog voltage signal converters, low-pass filter to filter out interference signal evacuation amplifiers, signal amplification evacuation die/number converter converts the digital signals sent from the input, single-chip microcomputer temperature control range by relay control heating equipment complete temperature control. This system of measuring range of 0 ° c to 99 ° c, temperature control system starts after the first press the first button to start the settings the lowest temperature, then the digital display temperature numerical intervals of one second temperature numerical increase once, when the user when the value of the minimum temperature settings and then press the a button to complete the minimum temperature settings, and so on through the second press Finish highest temperature settings. And temperature measurement system based on user-defined temperature range complete the range of temperature control.
2, temperaturedetection design
System temperature measurement using AD590 temperature sensor, AD590 is United States simulation component corporate production at both ends of the monolithic temperature sensor current source. Its main characteristics are as follows:
1, through the device of electric current (mA) is equal to the device environment thermodynamic temperature (Kelvin) degree; namely:, type: Ir — through the device (AD590) in-current, mA; T-thermodynamic temperature, K.
2, the measuring range for AD590-55 ° c to + 150 ° c;
3. the power supply voltage range AD590 to 4V ~ 30V;
4, the output resistance as 710MW;
5, high accuracy.
AD590 temperature sensor output signal amplification circuit magnification 10 x, and then fed into the die/number converter ADC0804, converted to SCM. According to the temperature sensor characteristics and AD590 enlarged 10 times the value of the voltage and the temperature of the scene found that actual temperature converted into single-chip value and press enter the numerical difference between a certain, die/number converter into microcontroller value is the key input worth 2.5 times. Because the SCM cannot be decimal multiplication, so the key input by 5, then the result of the operation and status of the program status word and then cycle to the right by one bit, if overflow flag bit is the low level directly on an accumulator belt carry cycle right, if the overflow flag bit to high level, the first to carry the standard bit CY location is high, then an additional loop belt carry, through these operations to the right so that the temperature value touchtone inputs and die/number converter into single-chip microcomputer temperature values of unity.
III. specific circuit connection as shown in the

4. software programming
Temperature control system consists of hardware and software components, building the hardware schematics to complete the power-on, we cannot realize temperature control, need to microcontroller programming, the following gives a temperature control system programming methods.

START: ANLP1, # 00H; display 00
JBP3.4, $; T0 = 0? a key press?
CALLDELAY1; eliminate jitter
JNBP3.4, $; T0 = 1? down?
MOVR0, # 00; initial value considering temperature pointer
L1: MOVA, R0; gauge temperature pointer into ACC
MOVP1, A; output to P1 display
MOVR5, # 10; delay 1 seconds
D1: MOVR7, # 248; 0.5 milliseconds
JNBP3.4, L2; 2nd press T0?
L2: CALLDELAY1; 2nd time by eliminating the jitter
JBP3.4, L3; releases are you yet?
; Jump to L3 stop
A lower limit MOV31H,; 31H temperature stored
JBP3.5, $; T1 = 0? a key press?
CALLDELAY1; eliminate jitter
$ JNBP3.5,;; T1 = 1? open?
MOVR0, # 00; initial value considering temperature pointer
L4: MOVA, RO; gauge temperature pointer into ACC
MOVP1, A; display 00
MOVR5, # 10; delay 1 seconds
D2: MOVR7, # 248; 0.5 milliseconds
JNBP3.5, L5; second press DJNZR7, $ T1?
L5: CALLDELAY1; 2nd time by eliminating the jitter
JBP3.5, L6; released? is the jump to L6
MOV30H, A; upper limit temperature into 30H
DELAY1: MOVR6, # 60; 30 milliseconds
MOV32H, # 0FFH; 32H old temperature storage
; For initial value
AAA: MOVX @ R0, A; BUS to high impedance
; Begin converting and ADC0804
WAIT: JBP2.0, ADC; testing whether the conversion is complete,
ADC: MOVXA, @ RO; will convert the value into the well
; Accumulator
MOV33H, A; will now temperature value deposited 33H
JCTDOWN; C = 0 to take into the larger value, said
; C = temperature rise, 1 indicates that the decline in
TUP: MOVA, 33H; now the temperature value into A
SUBBA, 30H; compare with upper limit temperature
JCLOOP; C = 1 means small than limit shall be
; Heating, C = 0 to stop than the upper limit, heating
TDOWN: MOVA, 33H; now the temperature value into A
SUBBA, lower temperature 31H; and for comparison
JNCLOOP; C = 1 indicates lower limit of small, than
; Heating, C = 0 represents the lower limit greater than
CLRP2.1; P2.1 action
MOVR4, # 0FFH; delay

5. conclusion:
This article gives the MCU in 0 ℃ ~ 99 ¡æ, through user settings temperature upper limit and lower limit values for certain range temperature control; gives a temperature control system hardware connection circuit and software programs, this system of temperature control is a single chip is widely used in the case of all trades, I believe that through our efforts, some intelligence and makes the application more extensive microcontroller.

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