23-11-2014, 08:19 PM
reguire temperature sensor using lm35 and adc ppt
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temperature sensor lm35 interfacing with adc ppt
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reguire temperature sensor using lm35 and adc ppt
24-11-2014, 10:42 PM
introduction
Digital thermometer is a good choice for beginners who just left the world of microcontrollers, because it provides an opportunity to learn using sensors to measure real world signals are analog in nature is. This article describes the project as based on microcontroller and temperature sensor LM35 PIC16F688. Is analogous to the LM35 sensor that converts the temperature to a proportional analog voltage. The output signal from the sensor is connected to one of the inputs of the ADC in a PIC16F688 microcontroller to obtain an equivalent temperature in digital format. the temperature is displayed in 16 x 2 character LCD, in either° c or° F scale.
theory
Temperature sensor LM35 series produced by National Semiconductor Corporation and designed to work over the -55° C to 150° c temperature range. These sensors do not require external calibration and output voltage is proportional to the temperature coefficient for temperature up to 10 MV voltage transformation° with LM35 series sensors come in different packages. the One I used TO-46 package hermatic transistor in which the metal housing is connected with the negative pin (GND).
Measuring negative temperatures (below 0° C) requires a negative voltage source. However, the project does not use any ESTA negative voltage source, and therefore demonstrates the use of the sensor for measurement of temperature above 0° C (up to 100° C).
The output voltage from the sensor into a digital signal 10-bit a/D CONVERTER using internal PIC16F688. Because the voltage shall be measured in the range from 0 to 1.0 a/D CONVERTERS in (that represents a range of maximum temperature: 100° c), the ADC requires a lower voltage reference (instead of the Vdd supply voltage = 5V) for A/D conversion in order to obtain higher accuracy below reference voltage can be set using the Zener diode, resistor network or just a simple diode. You can get an approximate reference voltage 1.2 in by connecting two diodes and resistor, voltage, as shown below. As a demonstration, I will use the schema in ESTA ESTA project. I measured the voltage output at the two diodes, as in 1196. resistor RI used 3.6 K, 1 k, but you can use too. it is important to measure the voltage at the two diodes are as accurate as possible.
We need to do some math to a/D conversion. Our Vref was 1.196, and 10-bit ADC. Thus, any input voltage from 0-1196, will appear in the digital ID Between 0 and 1023. resolution of the ADC 1196/1024 = 0.001168 V/graph. THUS, digital output corresponding to any input voltage Vin = Vin/0.001168. Now, let's see how to get the temperature back from ESTA overall conversion process the output signal at 10-bit digital code.
However, the ambient temperature is 26.4° c. output current would be 264 MB (0.264 in) ADC Output be 0.264./0.001168 = 226. If we change the ESTA, we have 226 with ADC, and we can go back and find the temperature sensor using a scale factor (10 MV/° c)
0.001168 temperature = 226 * (V/Count)/0.01 (V/° C) = 26.4° C
If you want personal respiratory floating point math in your program, just use
temperature = 226 * 1168 = 263968
When you display the ESTA, you need to put a decimal place in fourth from the left. So the design temperature is 26.3968° c, which is very close to the actual difference is caused by quantization and rounding errors. In this project, we will display the temperature to one decimal place, i.e., we divide the number by 1000 to get 263. So the temperature is to be displayed as 26.3° c
Once you have the temperature back to° C, you can convert it to° F, using the equation
Temperatures in° F = 9 x temperature in° C/5 + 32
In this case, the number you got for the° C scale 10 (263 to 26.3), you should use
Temperatures in° F = 9 x temperature in° C/5 + 320
So, the room for the C may not be exactly divided into 5 handler (for example, no 263), you can further eliminate float through it again at 10. So the new equation is,
Temperatures in° F = 9 x temperature in° c x 10/5 + 3200
or, the temperature in° F = 18 x temperature in° C + 18 = 3200 x 3200 + 263 = 7934
79.34° F is equivalent to 26.3° c within the framework of this project, it will be displayed as 79.3° F.
The concept of
External reference voltage for internal ADC PIC16F688 RA1-can be provided through the I/O pin sensor LM35. exit to reading and through RA2/AN2 channel ADC. The temperature is displayed on the LCD 16 x 2 characters, which operates in 4-bit mode.
Digital thermometer is a good choice for beginners who just left the world of microcontrollers, because it provides an opportunity to learn using sensors to measure real world signals are analog in nature is. This article describes the project as based on microcontroller and temperature sensor LM35 PIC16F688. Is analogous to the LM35 sensor that converts the temperature to a proportional analog voltage. The output signal from the sensor is connected to one of the inputs of the ADC in a PIC16F688 microcontroller to obtain an equivalent temperature in digital format. the temperature is displayed in 16 x 2 character LCD, in either° c or° F scale.
theory
Temperature sensor LM35 series produced by National Semiconductor Corporation and designed to work over the -55° C to 150° c temperature range. These sensors do not require external calibration and output voltage is proportional to the temperature coefficient for temperature up to 10 MV voltage transformation° with LM35 series sensors come in different packages. the One I used TO-46 package hermatic transistor in which the metal housing is connected with the negative pin (GND).
Measuring negative temperatures (below 0° C) requires a negative voltage source. However, the project does not use any ESTA negative voltage source, and therefore demonstrates the use of the sensor for measurement of temperature above 0° C (up to 100° C).
The output voltage from the sensor into a digital signal 10-bit a/D CONVERTER using internal PIC16F688. Because the voltage shall be measured in the range from 0 to 1.0 a/D CONVERTERS in (that represents a range of maximum temperature: 100° c), the ADC requires a lower voltage reference (instead of the Vdd supply voltage = 5V) for A/D conversion in order to obtain higher accuracy below reference voltage can be set using the Zener diode, resistor network or just a simple diode. You can get an approximate reference voltage 1.2 in by connecting two diodes and resistor, voltage, as shown below. As a demonstration, I will use the schema in ESTA ESTA project. I measured the voltage output at the two diodes, as in 1196. resistor RI used 3.6 K, 1 k, but you can use too. it is important to measure the voltage at the two diodes are as accurate as possible.
We need to do some math to a/D conversion. Our Vref was 1.196, and 10-bit ADC. Thus, any input voltage from 0-1196, will appear in the digital ID Between 0 and 1023. resolution of the ADC 1196/1024 = 0.001168 V/graph. THUS, digital output corresponding to any input voltage Vin = Vin/0.001168. Now, let's see how to get the temperature back from ESTA overall conversion process the output signal at 10-bit digital code.
However, the ambient temperature is 26.4° c. output current would be 264 MB (0.264 in) ADC Output be 0.264./0.001168 = 226. If we change the ESTA, we have 226 with ADC, and we can go back and find the temperature sensor using a scale factor (10 MV/° c)
0.001168 temperature = 226 * (V/Count)/0.01 (V/° C) = 26.4° C
If you want personal respiratory floating point math in your program, just use
temperature = 226 * 1168 = 263968
When you display the ESTA, you need to put a decimal place in fourth from the left. So the design temperature is 26.3968° c, which is very close to the actual difference is caused by quantization and rounding errors. In this project, we will display the temperature to one decimal place, i.e., we divide the number by 1000 to get 263. So the temperature is to be displayed as 26.3° c
Once you have the temperature back to° C, you can convert it to° F, using the equation
Temperatures in° F = 9 x temperature in° C/5 + 32
In this case, the number you got for the° C scale 10 (263 to 26.3), you should use
Temperatures in° F = 9 x temperature in° C/5 + 320
So, the room for the C may not be exactly divided into 5 handler (for example, no 263), you can further eliminate float through it again at 10. So the new equation is,
Temperatures in° F = 9 x temperature in° c x 10/5 + 3200
or, the temperature in° F = 18 x temperature in° C + 18 = 3200 x 3200 + 263 = 7934
79.34° F is equivalent to 26.3° c within the framework of this project, it will be displayed as 79.3° F.
The concept of
External reference voltage for internal ADC PIC16F688 RA1-can be provided through the I/O pin sensor LM35. exit to reading and through RA2/AN2 channel ADC. The temperature is displayed on the LCD 16 x 2 characters, which operates in 4-bit mode.
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