- LM35 is an analog, linear temperature sensor whose output voltage varies linearly with change in temperature.
- LM35 is three terminal linear temperature sensor from National semiconductors.
- It can measure temperature from-55 degree celsius to +150 degree celsius.
- The voltage output of the LM35 increases 10mV per degree Celsius rise in temperature.
- LM35 can be operated from a 5V supply and the stand by current is less than 60uA.
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Microcontrollers dont accept analog signals as their input directly.
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We need to convert this analog output signal to digital before we can feed it to a microcontroller’s input.
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For this purpose, we can use an ADC( Analog to Digital Converter).If we are using a basic microcontroller like 8051, we need to use an external ADC to convert analog output from LM35 to digital.
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We then feed the output of ADC ( converted digital value) to input of 8051.
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But modern day boards like Arduino and most modern day micro controllers come with inbuilt ADC.
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Our arduino uno has an in built 10 bit ADC (6 channel).
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We can make use of this in built ADC of arduino to convert the analog output of LM35 to digital output.
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Since Arduino uno has a 6 channel inbuilt ADC, there are 6 analog input pins numbered from A0 to A5.
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Connect analog out of LM35 to any of these analog input pins of arduino.
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Connect the +5v for LM35 can be taken from the +5v out pin of arduino uno.
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Also the ground pin of LM35 can be connected to GND pin of arduino uno.
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Connect Vout (the analog out of LM35) to any of the analog input pin of arduino uno.