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Sunday, May 22, 2011
Mechanical Refrigeration System
In refrigrasi mechanical vapor compression systems are a series of four main components: evaporator, compressor, condenser, and refrigerant flow control devices. Each component has a trait and its own function differently, but in an integrated and operate together will be able to move the thermal energy.
The impact of operating a refrigeration system on an object is, if picked up some of the energy contained in it, the temperature of the object will decrease. Conversely, because the refrigeration system operation is then a number of displaced thermal energy to the environment, the environment can become warmer.
The following is a brief description of the main components of a mechanical refrigeration system:
1. Condenser (condenser - CD)
Condenser is the component where the refrigerant phase change process occurs, the vapor phase into liquid phase. From the process of condensation (condensation) that occur in it that was then this component gets its name. The process of condensation will take place when the refrigerant to release the heat it contains.
Heat is released and discharged into the environment. In order for heat to escape into the environment, then the condensation temperature (TKD) should be higher than the ambient temperature (Tling). Because the refrigerant is a substance that is very volatile, so for him to be made of high pressure condensed. Thus, the condenser is the part where the high-pressure refrigerant (PKD = high pressure - HP).
2. Counterfeit expansion (expansion devices - Exd)
This tool serves as a gate that regulates how much liquid refrigerant is allowed to flow from the condenser to the evaporator. Therefore these tools are often also called refrigerant flow controller. In various textbooks of thermodynamics, processes occurring in these devices is usually called a throttling process.
The amount of refrigerant flow rate is one factor that determines the amount of refrigeration capacity. For a small refrigeration system, the refrigerant flow rate required is also small. Instead the unit or a large refrigeration system will have large refrigerant flow rate as well. There are several types of expansion devices. Below is assigned to some of them.
a. Capillary tube (capillary tube - CT).
Form of copper pipe with holes smaller than about 1 mm in diameter, with height adjusted with keperluannya up to several meters. At various refrigeration units that use these pipes are usually strung to protect them from damage and compact placement.
Hole narrow channel and capillary tube length is an obstacle to the flow of refrigerant through it; barriers that limit the amount of flow that's it. This capillary tube produces a constant flow.
b. Hand expansion valve (hand / manual expansion valve - HEV).
It is a form of flow regulator valve or faucet used to, which is operated to adjust the opening manually.
c. Thermostatic expansion valve (thermostatic expansion valve - TEV).
In this device there are parts that can work thermostatic, which has a temperature sensor attached to the output of the evaporator. Temperature changes that occur at the output of the evaporator is a major indicator of small refrigeration load. Temperature variation was used to set the aperture TeV, so that the flow rate through it also be controlled.
d. Float valve (float valve - FV).
Expansion devices of this type is usually coupled with the evaporator type of 'puddle' (flooded evaporator, wet evaporator). Height (level) of fluid in the reservoir (reservoir) to drive the evaporator liquid that floats into the regulator valve opening.
3. Evaporator (evaporator - EV)
Evaporator is the component where the liquid refrigerant that goes into it will evaporate. The process of vaporization (evaporation), it occurs because the liquid refrigerant absorbs heat, ie refrigeration system which is a burden. There are two types of evaporators are:
a. Direct expansion evaporators (direct / dry expansion type - DX).
In this evaporator there is a section, namely at the output, which is designed always awake 'dry', meaning in part that the berfasa liquid refrigerant evaporates before it has been sucked out into the compressor inlet.
b. Evaporator inundation (flooded / wet expansion type).
In this type of evaporator entire inner surface of the evaporator is always flooded, or touching, with the refrigerant is a liquid. There is a reservoir (reservoir, low pressure receiver), where the liquid refrigerant collected, and from the top of the reservoir the refrigerant vapor formed in the evaporator is sucked into the compressor.
4. Compressor (compressor - CP)
The impact of operating a refrigeration system on an object is, if picked up some of the energy contained in it, the temperature of the object will decrease. Conversely, because the refrigeration system operation is then a number of displaced thermal energy to the environment, the environment can become warmer.
The following is a brief description of the main components of a mechanical refrigeration system:
1. Condenser (condenser - CD)
Condenser is the component where the refrigerant phase change process occurs, the vapor phase into liquid phase. From the process of condensation (condensation) that occur in it that was then this component gets its name. The process of condensation will take place when the refrigerant to release the heat it contains.
Heat is released and discharged into the environment. In order for heat to escape into the environment, then the condensation temperature (TKD) should be higher than the ambient temperature (Tling). Because the refrigerant is a substance that is very volatile, so for him to be made of high pressure condensed. Thus, the condenser is the part where the high-pressure refrigerant (PKD = high pressure - HP).
2. Counterfeit expansion (expansion devices - Exd)
This tool serves as a gate that regulates how much liquid refrigerant is allowed to flow from the condenser to the evaporator. Therefore these tools are often also called refrigerant flow controller. In various textbooks of thermodynamics, processes occurring in these devices is usually called a throttling process.
The amount of refrigerant flow rate is one factor that determines the amount of refrigeration capacity. For a small refrigeration system, the refrigerant flow rate required is also small. Instead the unit or a large refrigeration system will have large refrigerant flow rate as well. There are several types of expansion devices. Below is assigned to some of them.
a. Capillary tube (capillary tube - CT).
Form of copper pipe with holes smaller than about 1 mm in diameter, with height adjusted with keperluannya up to several meters. At various refrigeration units that use these pipes are usually strung to protect them from damage and compact placement.
Hole narrow channel and capillary tube length is an obstacle to the flow of refrigerant through it; barriers that limit the amount of flow that's it. This capillary tube produces a constant flow.
b. Hand expansion valve (hand / manual expansion valve - HEV).
It is a form of flow regulator valve or faucet used to, which is operated to adjust the opening manually.
c. Thermostatic expansion valve (thermostatic expansion valve - TEV).
In this device there are parts that can work thermostatic, which has a temperature sensor attached to the output of the evaporator. Temperature changes that occur at the output of the evaporator is a major indicator of small refrigeration load. Temperature variation was used to set the aperture TeV, so that the flow rate through it also be controlled.
d. Float valve (float valve - FV).
Expansion devices of this type is usually coupled with the evaporator type of 'puddle' (flooded evaporator, wet evaporator). Height (level) of fluid in the reservoir (reservoir) to drive the evaporator liquid that floats into the regulator valve opening.
3. Evaporator (evaporator - EV)
Evaporator is the component where the liquid refrigerant that goes into it will evaporate. The process of vaporization (evaporation), it occurs because the liquid refrigerant absorbs heat, ie refrigeration system which is a burden. There are two types of evaporators are:
a. Direct expansion evaporators (direct / dry expansion type - DX).
In this evaporator there is a section, namely at the output, which is designed always awake 'dry', meaning in part that the berfasa liquid refrigerant evaporates before it has been sucked out into the compressor inlet.
b. Evaporator inundation (flooded / wet expansion type).
In this type of evaporator entire inner surface of the evaporator is always flooded, or touching, with the refrigerant is a liquid. There is a reservoir (reservoir, low pressure receiver), where the liquid refrigerant collected, and from the top of the reservoir the refrigerant vapor formed in the evaporator is sucked into the compressor.
4. Compressor (compressor - CP)
The compressor is a component which is the heart of the refrigeration system. Compressors work sucking the refrigerant vapor from the evaporator and pushed by means of compression to flow into the condenser.
Because the refrigerant compressor drain device expansion while restricting the flow, then in between these two components were stirred pressure difference, namely: the condenser refrigerant pressure is high (high pressure - HP), while in the evaporator refrigerant pressure is low (low pressure - LP).
Because the refrigerant compressor drain device expansion while restricting the flow, then in between these two components were stirred pressure difference, namely: the condenser refrigerant pressure is high (high pressure - HP), while in the evaporator refrigerant pressure is low (low pressure - LP).
Mechanical Refrigeration System
PLC (Programmable Logic Controller) - An Introduction
PLC (Programmable Logic Controller) was first introduced in 1969 by Richard E. Morley who was the founder of Modicon Corporation. According to the National Electrical Manufacturing Association (NEMA) PLC is defined sebagasi a digital electronic device with a programmable memory to store instructions that perform specific functions such as logic, sequence, timing, counting, and arithmetic to control an industrial machine or process in accordance with the desired industry.
PLC is capable of doing a continuous process based on input variables and provide the programming decisions at will so that the value of output under control.
PLC is a "special computer" for applications in industry, to monitor the process, and to replace the hard wiring controls and has its own programming language. But the PLC is not the same because the PLC will be a personal computer designed for installation and maintenance by a technician and an electrician in the industry who do not have to have a high electronics skills and provide flexibility based on the instruction execution control logic.
That's why the PLC is increasingly well developed in terms of number of inputs and outputs, the amount of available memory, speed, communication between the PLC and how or programming techniques. Almost all kinds of production processes in industry can be automated using a PLC.
The speed and accuracy of operation can be increased so much better using this control system. The advantage of PLC is its ability to change and replicate the process at the same operation with the communication and information-gathering vital information.
Operations on the PLC consists of four essential parts:
1. observation value of inputs
2. run program
3. provides output value
4. control
From an excess of PLC also has shortcomings, among others, which often highlighted is that to program a PLC takes someone who is skilled and fully understands what is needed by the plant and understand about the security or safety that must be met.
Meanwhile, a trained person like that is quite rare and the programming must be made directly to the place where the servers are connected to the PLC, while it is not unusual location of the computer playing it in dangerous places. Therefore we need a device capable of observing, edit and run programs remotely.
PLC is capable of doing a continuous process based on input variables and provide the programming decisions at will so that the value of output under control.
PLC is a "special computer" for applications in industry, to monitor the process, and to replace the hard wiring controls and has its own programming language. But the PLC is not the same because the PLC will be a personal computer designed for installation and maintenance by a technician and an electrician in the industry who do not have to have a high electronics skills and provide flexibility based on the instruction execution control logic.
That's why the PLC is increasingly well developed in terms of number of inputs and outputs, the amount of available memory, speed, communication between the PLC and how or programming techniques. Almost all kinds of production processes in industry can be automated using a PLC.
The speed and accuracy of operation can be increased so much better using this control system. The advantage of PLC is its ability to change and replicate the process at the same operation with the communication and information-gathering vital information.
Operations on the PLC consists of four essential parts:
1. observation value of inputs
2. run program
3. provides output value
4. control
From an excess of PLC also has shortcomings, among others, which often highlighted is that to program a PLC takes someone who is skilled and fully understands what is needed by the plant and understand about the security or safety that must be met.
Meanwhile, a trained person like that is quite rare and the programming must be made directly to the place where the servers are connected to the PLC, while it is not unusual location of the computer playing it in dangerous places. Therefore we need a device capable of observing, edit and run programs remotely.
PLC (Programmable Logic Controller) - An Introduction
Temperature data acquisition using microcontroller
Abstract
This paper discusses the design of the temperature data acquisition system that uses a component-konponen basic form of a temperature sensor, microcontroller and LCD as the viewer facility. Temperature data acquisition system into the one thing that is very important in industrial activity, because it is a small part of a process control.
With regard to the importance of the system, then the design temperature data acquisition system capable of monitoring the temperature of a plant. Data to be measured is a temperature so that the physical quantities to be processed and displayed in the form of electrical systems used LM35 temperature sensor that is able to convert these quantities with the increase of 10mV / º C.
To be able to design the system was first carried out the process to change the temperature into an analog voltage using a temperature sensor LM35. After going through the process boosted by the signal conditioning, analog voltage is converted into digital data using the ADC 0804.
Digital data acquired and processed by the microcontroller AT89S51 and displayed, so that got a plant with information about the temperature unit ° C on an LCD. From the temperature data acquisition system design showed that this system has the ability to measure the temperature from 25 º C to 100 º C with an average error of 0.2125 appointment temperature ° C.
Keywords: Acquisition of temperature data, LM35 temperature sensor, microcontroller AT89S51
I. INTRODUCTION
1.1 Background
Instrumentation systems that form the data acquisition has been widely used in industrial activities, as part of the process control. Measurement of physical quantities is one step in the acquisition of data.
Temperature is one of the physical quantities are often used in a control system is good only for a monitoring system alone or to further control the process.
In connection with this, then we make a temperature sensor that can be controlled by a microcontroller. By displaying a measurement result digitally, monitoring of the process can be conducted more easily.
1.2.1 Objectives
Designing a data acquisition system for temperature and then displayed on the LCD using a Microcontroller AT89S51.
1.3 Limitation Problem
In making this task the authors limited the problem as follows:
1. Range data acquisition is 25 º C to 100 º C.
2. Measurement data is displayed on an LCD as the monitoring equipment without performing process control.
3. ADC configuration set free running.
II. BASIC THEORY
2.1.1 Temperature Sensor LM 35
To detect the temperature used an LM 35 temperature sensor that can be directly calibrated in ° C, the LM 35 is functioned as the basic temperature sensors. Vout from the LM 35 is associated with ADC (Analog To Digital Converter). In room temperature (25 ° C) transducer is capable of removing the voltage 250mV and 1.5 V at a temperature of 150 ° C with an increase of 10mV / ° C.
2.2 Operational Amplifiers (Operational Amplifiers)
Operational amplifiers are integrated circuits (IC) which has 5 basic terminal. Two terminals for power supply, 2 the other is used for the input signal in the form of reverse input (-) and no reverse input (+) and 1 terminal for output.
2.2.1 No Reverse Amplifier (Non-inverting Amplifier)
Not reverse the amplifier is an amplifier where output voltage or the Vo have the same polarity or input voltage Vi. I currents flowing into the Ri as input impedance op - amp is very large so that no current flows on both the input terminals. Voltage at Ri equal to Vi because of differences in the two terminal input voltage approaches 0 V.
i = (2.5)
Voltage at Rf can be expressed as
VRF = I Rf = (2.6)
The output voltage Vo is obtained by adding the voltage at which Ri Vi to the voltage at the Rf of VRF.
Vo = Vi + Vi (2.7)
2.2.2 Differential Amplifier
Differential amplifier is an amplifier where output voltage or the Vo is the result of the difference between the two pieces of input voltage at the inverting terminal and non-invertingnya.
2.3 The series of Analog to Digital Converter (ADC)
ADC in this design is used to convert the input analog output temperature sensor that has been amplified into 8-bit digital data. Type ADC ADC 0804 is used in working mode free running. To create a working mode into free running ADC 0804, it must be known how the sequence of values on and change the value on.
Working mode free running ADC is obtained if and connected to ground in order to always get a logic 0 so that the ADC will always be active and ready to provide data. Pin and rolled into one because of changes in the same logic on logic changes, thus providing the logic to be done automatically by the output.
2.4 Microcontroller AT89S51
AT89S51 is an 8 bit microcontroller is made of CMOS, which is to consume low power and high ability. This microcontroller has a 4Kbyte In-System Programmable Flash Memory, RAM is 128 bytes, 32 input / output, watchdog timer, two data registers pointers, two 16-bit timers and counters, five interrupt vectors, a full-duplex serial port, on-chip oscillator and clock circuit.
AT89S51 made with non-volatile memory technology with high density by Atmel. Microcontroller is suitable to the instruction set and pinout industry standard 80C51.
On-chip flash memory allows the program to re-programmed with the usual nonvolatile memory programmer.
Description:
Vcc: Supply Voltage
GND: Ground or earth
RST: Reset input. Condition logic '1 'during the engine cycle when the oscillator work and will reset the microcontroller in question.
Function - function Port:
Port 0: 8 bit parallel port is open drain in both directions. When used to access the external memory, this port will memultipleks memory address with the data.
Port 1: an 8-bit parallel port, two-way that can be used for various purposes.
Port 2: an 8-bit wide parallel port is bidirectional. These ports make deliveries byte address when done accessing external memory.
P3.0: Shared serial input
P3.1: saluaran serial output
P3.2: External Interrupt 0
P3.3: External Interrupt 1
P3.4: Input external timer / counter 0
P3.5: Input external timer / counter 1
P3.6: Signal punctuation ekstrenal data memory.
P3.7: Signal sign write external data memory.
III. DESIGN SYSTEM
3.1 Hardware Design
3.1.1 Temperature Sensor (LM35)
LM35 temperature sensor serves to change the temperature of physical quantities in the form of a magnitude electrical voltage. This sensor has a parameter that each increase of 1 º C increase by 10mV of output voltage with a maximum limit of the sensor output is 1.5 V at a temperature of 150 ° C.
In the design we set the adc output reaches full scale when the temperature of 100 ° C, so that when the temperature is 100 ° C. The transducer output voltage (10mV / ° C x 100 ° C) = 1V.
From direct current measurements at room temperature, LM35 output is 0.3V (300mV). This voltage is processed by using a signal conditioning circuit to match the ADC input stage.
3.1.2 Signal conditioning
Signal conditioner works to strengthen the LM35 temperature sensor output voltage to be able to be processed on the next equipment in this case by the ADC 0804.
Desirable that the temperature measurement can be performed in the range of 25 ° C - 100 ° C, whereas at room temperature LM35 has issued a voltage of 0.3 V, so to be able to arrange for the ADC input at 0V at room temperature, added a differential amplifier.
Differential amplifier output boosted again with the non-inverting amplifier circuit. With Vin = 1V at 100 ° C and the desired Vout at 5V (VX) are used to determine the value of resistance to non-inverting amplifier as follows:
If Ri = 1K then, Rf = 4K 50K potentiometer is used in applications for Rf.
3.1.3 Analog to Digital Converter (ADC 0804)
Adc circuit design to be used mode free running. This mode was chosen because of adc conversion time is much faster on the level of temperature change of the plant, so that every time the temperature changes, adc always been completed to convert the data so that data is valid for sampled.
For ADC 0804 with the number of bits by 8 bits and Vref = 5V then the resolution (ΔV) = 5 x 2-8 = 19.53 mV.
Adc analog voltage input from the output at full scale signal conditioning in the amount of VX can be calculated as follows:
thus when the input voltage adc adc output would be worth 4.9804 FFH.
3.1.4 Microcontroller (AT89S51)
8 bit digital data from the ADC is taken by mikokontroller through Port 2 (P2.0-P2.7 are connected to DB0-DB7). While the input data for the LCD viewer is removed through Port 1 (P1.0-P1.7 are connected to D0-D7). To control the foot RS and E on the LCD microcontroller use P3.6 and P3.7 foot
The process of data acquisition and data processing can be seen in figure 7. Data taken from P2 calibrated beforehand, after the calibrated data is then converted into ASCII code 0-100 so displayed on the LCD, if not changed then the numbers displayed are 0-255.
IV. TESTING AND ANALYSIS
4.1 Testing of each block
4.1.1 Testing LM35
LM35 temperature sensor is tested by providing a 5V supply and provide indirect heating, while the output voltage directly observed with a voltmeter. From the test data obtained as follows.
Table 2. The test results LM35 sensor
The output voltage temperature
35 ° C 00:35
40 ° C 00:40
45 ° C 00:45
50 ° C 12:51
55 ° C 00:55
60 ° C 0.65
65 ° C 0.71
70 ° C 0.76
From the test results are known voltage sensor output increased by 50mV for every 5 ° C or 10mV / ° C, the sensor is working properly.
4.1.2 Testing the signal conditioning circuit
Signal conditioning circuit testing is done by providing the voltage change at the end of the amplifier input (non-inverting amplifier) and then measure the output to then calculated the level of reinforcement stress.
Table 3. The test result signal conditioner
Av = Vout Vin (Vout / Vin)
0.1 V 0.5 V 5
0.2 V 1V 5
0.3 V 1.5 V 5
0.4 V 2V 5
0.5 V 2.5 V 5
0.6 V 3V 5
0.7 V 2.5 V 5
From the data table is known that the level of strengthening the signal conditioning circuit voltage is 5 times, then the circuit has to work properly.
4.1.3 Testing ADC 0804
Testing is done by giving voltage to the ADC input and record the output of digital data generated through an 8-bit LED display.
Table 4. ADC test results.
Digital data input voltage
0.6 v 23 H
1.2 41 v H
1.8 62 v H
2.6 v H 8D
3.4 v B7 H
4 v DF H
4.2 v EF H
FF v 4.9 H
ADC data test results indicate that these components can work well.
4.1.4 Software Testing
Software testing program involved testing of the temperature data acquisition and calibration of data acquisition of temperature on the LCD display. The process of testing done by looking at the digital data visually displayed on the LED indicator is the data acquired and comparing the results of the temperature display on the LCD.
Table 5. Results of testing temperature display
Digital temperature displays temperature data calculated
25 H 35 ° C 35.294 ° C
43 H 44 ° C 44.117 ° C
63 H 53 ° C 53.823 ° C
8D H 66 ° C 66.470 ° C
B7 H 78 ° C 78.823 ° C
DF H 90 ° C 90.588 ° C
EF H 95 ° C 95.294 ° C
FF H 100 ° C 100 ° C
From the table note that the temperature displayed on the LCD with the temperature of the calculation there is a difference in terms of accuracy, where the temperature is displayed on the LCD is a rounded value without displaying the value behind the comma, while the temperature is calculated as the temperature standard that must be displayed. Removal of the coma is intended to facilitate the process of making the program, but with the consequences of error rates due to the removal of the displayed temperature. Software has to calibrate the digital data and displays the temperature value of a plant, then the software has to work properly.
4.2 Testing the overall system
Testing the overall system is done by placing the sensor LM35 and thermometers in the temperature of the same plant and then compares the temperature is displayed on the LCD appointment to appointment of temperature on the thermometer for 30 minutes.
Table 6. Results of testing system
Display temperature
LCD temperature display thermometer Error
30 ° C 29.7 ° C 0.3 ° C
32 ° C 32 ° C 0 ° C
34 ° C 34 ° C 0 ° C
37 ° C 37.5 ° C 0.5 ° C
40 ° C 40 ° C 0 ° C
45 ° C 45.6 ° C 0.6 ° C
46 ° C 46 ° C 0 ° C
47 ° C 46.7 ° C 0.3 ° C
error 1.7 ° C
The results showed that the temperature data acquisition system has an average error of 0.2125 ° C, this value is obtained by summing all the error value of each test divided by the number of tests (8 times).
V. CLOSING
5.1.1 Conclusion
From the design and manufacture of temperature acquisition system device can be concluded that - as follows:
1. ADC Test results indicate that for input of 4.9 V digital data has reached FFH, then the designation will result in errors when the temperature where the input voltage 4.9 V displays the temperature has reached 100 ° C.
2. Error average temperature on the appointment of the temperature data acquisition system is 0.2125 ° C.
3. LM35 has a sensor output voltage with an increase of 50 mV for every 5 ° C or 10 mV / ° C, the sensor has a fairly linear increase.
5.2 Suggestions
1. At the output end signal conditioning circuit should be added clipper circuit which serves to limit the ADC input for a maximum of 5V.
2. To simplify the zero setting of the differential amplifier circuit output LM35 should be strengthened so that the first reference voltage reduction is not too small.
3. Reference voltage source deduction should use a zener diode to obtain a stable voltage.
4. To make more precise temperature data view, the calibration program can be made better temperature data.
This paper discusses the design of the temperature data acquisition system that uses a component-konponen basic form of a temperature sensor, microcontroller and LCD as the viewer facility. Temperature data acquisition system into the one thing that is very important in industrial activity, because it is a small part of a process control.
With regard to the importance of the system, then the design temperature data acquisition system capable of monitoring the temperature of a plant. Data to be measured is a temperature so that the physical quantities to be processed and displayed in the form of electrical systems used LM35 temperature sensor that is able to convert these quantities with the increase of 10mV / º C.
To be able to design the system was first carried out the process to change the temperature into an analog voltage using a temperature sensor LM35. After going through the process boosted by the signal conditioning, analog voltage is converted into digital data using the ADC 0804.
Digital data acquired and processed by the microcontroller AT89S51 and displayed, so that got a plant with information about the temperature unit ° C on an LCD. From the temperature data acquisition system design showed that this system has the ability to measure the temperature from 25 º C to 100 º C with an average error of 0.2125 appointment temperature ° C.
Keywords: Acquisition of temperature data, LM35 temperature sensor, microcontroller AT89S51
I. INTRODUCTION
1.1 Background
Instrumentation systems that form the data acquisition has been widely used in industrial activities, as part of the process control. Measurement of physical quantities is one step in the acquisition of data.
Temperature is one of the physical quantities are often used in a control system is good only for a monitoring system alone or to further control the process.
In connection with this, then we make a temperature sensor that can be controlled by a microcontroller. By displaying a measurement result digitally, monitoring of the process can be conducted more easily.
1.2.1 Objectives
Designing a data acquisition system for temperature and then displayed on the LCD using a Microcontroller AT89S51.
1.3 Limitation Problem
In making this task the authors limited the problem as follows:
1. Range data acquisition is 25 º C to 100 º C.
2. Measurement data is displayed on an LCD as the monitoring equipment without performing process control.
3. ADC configuration set free running.
II. BASIC THEORY
2.1.1 Temperature Sensor LM 35
To detect the temperature used an LM 35 temperature sensor that can be directly calibrated in ° C, the LM 35 is functioned as the basic temperature sensors. Vout from the LM 35 is associated with ADC (Analog To Digital Converter). In room temperature (25 ° C) transducer is capable of removing the voltage 250mV and 1.5 V at a temperature of 150 ° C with an increase of 10mV / ° C.
2.2 Operational Amplifiers (Operational Amplifiers)
Operational amplifiers are integrated circuits (IC) which has 5 basic terminal. Two terminals for power supply, 2 the other is used for the input signal in the form of reverse input (-) and no reverse input (+) and 1 terminal for output.
2.2.1 No Reverse Amplifier (Non-inverting Amplifier)
Not reverse the amplifier is an amplifier where output voltage or the Vo have the same polarity or input voltage Vi. I currents flowing into the Ri as input impedance op - amp is very large so that no current flows on both the input terminals. Voltage at Ri equal to Vi because of differences in the two terminal input voltage approaches 0 V.
i = (2.5)
Voltage at Rf can be expressed as
VRF = I Rf = (2.6)
The output voltage Vo is obtained by adding the voltage at which Ri Vi to the voltage at the Rf of VRF.
Vo = Vi + Vi (2.7)
2.2.2 Differential Amplifier
Differential amplifier is an amplifier where output voltage or the Vo is the result of the difference between the two pieces of input voltage at the inverting terminal and non-invertingnya.
2.3 The series of Analog to Digital Converter (ADC)
ADC in this design is used to convert the input analog output temperature sensor that has been amplified into 8-bit digital data. Type ADC ADC 0804 is used in working mode free running. To create a working mode into free running ADC 0804, it must be known how the sequence of values on and change the value on.
Working mode free running ADC is obtained if and connected to ground in order to always get a logic 0 so that the ADC will always be active and ready to provide data. Pin and rolled into one because of changes in the same logic on logic changes, thus providing the logic to be done automatically by the output.
2.4 Microcontroller AT89S51
AT89S51 is an 8 bit microcontroller is made of CMOS, which is to consume low power and high ability. This microcontroller has a 4Kbyte In-System Programmable Flash Memory, RAM is 128 bytes, 32 input / output, watchdog timer, two data registers pointers, two 16-bit timers and counters, five interrupt vectors, a full-duplex serial port, on-chip oscillator and clock circuit.
AT89S51 made with non-volatile memory technology with high density by Atmel. Microcontroller is suitable to the instruction set and pinout industry standard 80C51.
On-chip flash memory allows the program to re-programmed with the usual nonvolatile memory programmer.
Description:
Vcc: Supply Voltage
GND: Ground or earth
RST: Reset input. Condition logic '1 'during the engine cycle when the oscillator work and will reset the microcontroller in question.
Function - function Port:
Port 0: 8 bit parallel port is open drain in both directions. When used to access the external memory, this port will memultipleks memory address with the data.
Port 1: an 8-bit parallel port, two-way that can be used for various purposes.
Port 2: an 8-bit wide parallel port is bidirectional. These ports make deliveries byte address when done accessing external memory.
P3.0: Shared serial input
P3.1: saluaran serial output
P3.2: External Interrupt 0
P3.3: External Interrupt 1
P3.4: Input external timer / counter 0
P3.5: Input external timer / counter 1
P3.6: Signal punctuation ekstrenal data memory.
P3.7: Signal sign write external data memory.
III. DESIGN SYSTEM
3.1 Hardware Design
3.1.1 Temperature Sensor (LM35)
LM35 temperature sensor serves to change the temperature of physical quantities in the form of a magnitude electrical voltage. This sensor has a parameter that each increase of 1 º C increase by 10mV of output voltage with a maximum limit of the sensor output is 1.5 V at a temperature of 150 ° C.
In the design we set the adc output reaches full scale when the temperature of 100 ° C, so that when the temperature is 100 ° C. The transducer output voltage (10mV / ° C x 100 ° C) = 1V.
From direct current measurements at room temperature, LM35 output is 0.3V (300mV). This voltage is processed by using a signal conditioning circuit to match the ADC input stage.
3.1.2 Signal conditioning
Signal conditioner works to strengthen the LM35 temperature sensor output voltage to be able to be processed on the next equipment in this case by the ADC 0804.
Desirable that the temperature measurement can be performed in the range of 25 ° C - 100 ° C, whereas at room temperature LM35 has issued a voltage of 0.3 V, so to be able to arrange for the ADC input at 0V at room temperature, added a differential amplifier.
Differential amplifier output boosted again with the non-inverting amplifier circuit. With Vin = 1V at 100 ° C and the desired Vout at 5V (VX) are used to determine the value of resistance to non-inverting amplifier as follows:
If Ri = 1K then, Rf = 4K 50K potentiometer is used in applications for Rf.
3.1.3 Analog to Digital Converter (ADC 0804)
Adc circuit design to be used mode free running. This mode was chosen because of adc conversion time is much faster on the level of temperature change of the plant, so that every time the temperature changes, adc always been completed to convert the data so that data is valid for sampled.
For ADC 0804 with the number of bits by 8 bits and Vref = 5V then the resolution (ΔV) = 5 x 2-8 = 19.53 mV.
Adc analog voltage input from the output at full scale signal conditioning in the amount of VX can be calculated as follows:
thus when the input voltage adc adc output would be worth 4.9804 FFH.
3.1.4 Microcontroller (AT89S51)
8 bit digital data from the ADC is taken by mikokontroller through Port 2 (P2.0-P2.7 are connected to DB0-DB7). While the input data for the LCD viewer is removed through Port 1 (P1.0-P1.7 are connected to D0-D7). To control the foot RS and E on the LCD microcontroller use P3.6 and P3.7 foot
The process of data acquisition and data processing can be seen in figure 7. Data taken from P2 calibrated beforehand, after the calibrated data is then converted into ASCII code 0-100 so displayed on the LCD, if not changed then the numbers displayed are 0-255.
IV. TESTING AND ANALYSIS
4.1 Testing of each block
4.1.1 Testing LM35
LM35 temperature sensor is tested by providing a 5V supply and provide indirect heating, while the output voltage directly observed with a voltmeter. From the test data obtained as follows.
Table 2. The test results LM35 sensor
The output voltage temperature
35 ° C 00:35
40 ° C 00:40
45 ° C 00:45
50 ° C 12:51
55 ° C 00:55
60 ° C 0.65
65 ° C 0.71
70 ° C 0.76
From the test results are known voltage sensor output increased by 50mV for every 5 ° C or 10mV / ° C, the sensor is working properly.
4.1.2 Testing the signal conditioning circuit
Signal conditioning circuit testing is done by providing the voltage change at the end of the amplifier input (non-inverting amplifier) and then measure the output to then calculated the level of reinforcement stress.
Table 3. The test result signal conditioner
Av = Vout Vin (Vout / Vin)
0.1 V 0.5 V 5
0.2 V 1V 5
0.3 V 1.5 V 5
0.4 V 2V 5
0.5 V 2.5 V 5
0.6 V 3V 5
0.7 V 2.5 V 5
From the data table is known that the level of strengthening the signal conditioning circuit voltage is 5 times, then the circuit has to work properly.
4.1.3 Testing ADC 0804
Testing is done by giving voltage to the ADC input and record the output of digital data generated through an 8-bit LED display.
Table 4. ADC test results.
Digital data input voltage
0.6 v 23 H
1.2 41 v H
1.8 62 v H
2.6 v H 8D
3.4 v B7 H
4 v DF H
4.2 v EF H
FF v 4.9 H
ADC data test results indicate that these components can work well.
4.1.4 Software Testing
Software testing program involved testing of the temperature data acquisition and calibration of data acquisition of temperature on the LCD display. The process of testing done by looking at the digital data visually displayed on the LED indicator is the data acquired and comparing the results of the temperature display on the LCD.
Table 5. Results of testing temperature display
Digital temperature displays temperature data calculated
25 H 35 ° C 35.294 ° C
43 H 44 ° C 44.117 ° C
63 H 53 ° C 53.823 ° C
8D H 66 ° C 66.470 ° C
B7 H 78 ° C 78.823 ° C
DF H 90 ° C 90.588 ° C
EF H 95 ° C 95.294 ° C
FF H 100 ° C 100 ° C
From the table note that the temperature displayed on the LCD with the temperature of the calculation there is a difference in terms of accuracy, where the temperature is displayed on the LCD is a rounded value without displaying the value behind the comma, while the temperature is calculated as the temperature standard that must be displayed. Removal of the coma is intended to facilitate the process of making the program, but with the consequences of error rates due to the removal of the displayed temperature. Software has to calibrate the digital data and displays the temperature value of a plant, then the software has to work properly.
4.2 Testing the overall system
Testing the overall system is done by placing the sensor LM35 and thermometers in the temperature of the same plant and then compares the temperature is displayed on the LCD appointment to appointment of temperature on the thermometer for 30 minutes.
Table 6. Results of testing system
Display temperature
LCD temperature display thermometer Error
30 ° C 29.7 ° C 0.3 ° C
32 ° C 32 ° C 0 ° C
34 ° C 34 ° C 0 ° C
37 ° C 37.5 ° C 0.5 ° C
40 ° C 40 ° C 0 ° C
45 ° C 45.6 ° C 0.6 ° C
46 ° C 46 ° C 0 ° C
47 ° C 46.7 ° C 0.3 ° C
error 1.7 ° C
The results showed that the temperature data acquisition system has an average error of 0.2125 ° C, this value is obtained by summing all the error value of each test divided by the number of tests (8 times).
V. CLOSING
5.1.1 Conclusion
From the design and manufacture of temperature acquisition system device can be concluded that - as follows:
1. ADC Test results indicate that for input of 4.9 V digital data has reached FFH, then the designation will result in errors when the temperature where the input voltage 4.9 V displays the temperature has reached 100 ° C.
2. Error average temperature on the appointment of the temperature data acquisition system is 0.2125 ° C.
3. LM35 has a sensor output voltage with an increase of 50 mV for every 5 ° C or 10 mV / ° C, the sensor has a fairly linear increase.
5.2 Suggestions
1. At the output end signal conditioning circuit should be added clipper circuit which serves to limit the ADC input for a maximum of 5V.
2. To simplify the zero setting of the differential amplifier circuit output LM35 should be strengthened so that the first reference voltage reduction is not too small.
3. Reference voltage source deduction should use a zener diode to obtain a stable voltage.
4. To make more precise temperature data view, the calibration program can be made better temperature data.
Temperature data acquisition using microcontroller