It represents each 1 Celsius degree by 10 mV, so that if the temperature is 20 Celsius degrees, then the output voltage of the LM35 will be (20*10mV=200mV). The LM35 output voltage is linearly proportional to the temperature. So take care not to connect the sensor in reversed pin order.
Important note: The pin-out diagram above (which is the same of the datasheet) is showing the sensor pin-out from the bottom view. Where Vs is connected to the high voltage (VCC), GND is connected to GND and Vout is connected to the Input channel of the Atmega32 ADC It has 3 pins assigned as demonstrated in the below diagram. LM35D is a temperature sensor of the LM35 temperature sensors family. The input channels are multiplexed over the pins of port A of the ATmega32. So, at each conversion, you should first choose the input channel to convert before starting the conversion. This means that you can connect up to eight analog input signals to the Atmega32 ADC, but at each conversion, only one channel input is converted. In this article, we will use the internal reference voltage so we will not need this step.ĪDC of the Atmega32 can accept inputs from up to eight channels.
(Even if you choose to use the internal voltage or the AVCC) Also, it is preferable to connect a capacitor between AREF and GND so that the reference voltage of the ADC is more stable and not affected by noise.These 2 connections make the supply voltage of the ADC more stable and not easily fluctuated by noise. If conversion accuracy is critical all the time, it is preferable that you connect a coil between the 2 pins and a capacitor between AVCC and GND.This is because the ADC gets its power supply from the AVCC pin. You should make sure that pins (VCC & AVCC) that are pins (10 & 30) are connected.Hardware Requirements:īefore using the ADC of the Atmeg32 there are a few hardware connections required in the circuit so that you can get the best results: Finally, you can use your own customized reference voltage by connecting a voltage source that has the same value as the reference voltage you want to the pin AREF (pin32).Ĭhoosing between these three sources of reference voltage happens while configuring the ADMUX register as we will explain later in this article.The AVCC pin can be your reference voltage, but this pin must be connected to the VCC and in this case, your reference voltage is the VCC.This voltage is set to 2.56V and cannot be changed. An internal voltage from within the Atmega32 MCU.
In Atmega32 you can use one of three sources for the reference voltage: The reference voltage is the maximum voltage you are expecting to receive from the sensor on the input channel of the ADC. By the end of this article, we will be able to make a simple fire alarmthat triggers a buzzer when the temperature exceeds a certain limit (60 Celsius degrees as an example). As an example of an analog signal, we shall use the output signal coming out of the LM35 temperature sensor. In this article, we shall learn about using the ADC of the Atmega32 to convert an analog signal to a digital one. In order to do that we need a device called an ADC ( Analog to Digital Converter) and fortunately, many controllers now have this device built-in. When dealing with such sensors we have to convert the analog signal coming out of them into digital words of ones and zeros so that our microcontroller can process it and make decisions based on it. Using LM35 Sensor and Atmega32 ADC to measure TemperatureĪnalog to digital conversion is generally needed whenever we deal with a sensor that produces an analog output (for example: LM35 temperature sensor), which is the case for a wide range of sensors.
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