Electrical – Temperature conversion ADC0804 and LM35


I'm doing this conversion and I have a problem. I must convert from 0°C to 30°C, and I know that the LM35 bring me 10mv/°C. Therefore, if the temp=30°C, the Vout=0,3V=Vmax. I amplify this output with the LM741 with a gain G=16,7, because like this my Vmax=5V. The output of the OPAMP goes directly to the ADC0804.

My question is: How do I do to show the temperature value in two display BCD 7-seg? What's the combinatorial circuit that I need to build?
I don't know how to pass from binary to BCD and also use only 5 bits to goes from 0 to 32.

Best Answer

My first response is that you should probably move up to a more modern approach to this project. Using LM35's and LM741's is technology that is about 35 years old. You can do a lot better and much more simply that messing around with the likes if these ancient analogue parts.

Research digital temperature sensors that have an I2C interface using just two digital signals. There are a plethora of candidate chips to use for this and they will provide you a wide range measurement capability often with resolution down to 0.125 degrees.

The temperature sensor with the I2C interface is then connected to an MCU of your choice. The display is in turn connected to the MCU and software takes care of reading temp values from the sensor and sending the values formatted to the display. Again there are scads of MCU choices and display choices can range from LED segment, LCD character or OLED graphic.