problem converting LM35 value

[bpramod]

Hello everyone, I want to read temperature from LM35 for my project. I am using p89v51rd2 microcontroller. As it doesn't have ADC, I have connected the output of LM35 to ADC0804. I am giving the output of this(8 bits) to port 2 of MC. But I am getting the output as 10H for room temperature. Is it correct value? How do I convert it to degree celcius?

 

[alexan_e]

What is the reference voltage of your ADC?
Are you using the basic configuration?

Alex

 

[ark5230]

Does the output / reading change with temperature changes ?

 

[bpramod]

What is the reference voltage of your ADC?
Are you using the basic configuration?

Alex

Vref of ADC 0804 is 2.5 volts according to the data sheet..and i m not getting output changes with respect to the temperature changes....

 

[poorchava]

You are talking about this part: **broken link removed**, right? Then where did you get the information that it has internal reference voltage source? The datasheet states that it WORKS with 2V5 or 5V reference, not that it CONTAINS one. Get some 2V5 voltage reference (because LM35 output is generally in the range of 0V to 1V).

 

[bpramod]

You are talking about this part: **broken link removed**, right? Then where did you get the information that it has internal reference voltage source? The datasheet states that it WORKS with 2V5 or 5V reference, not that it CONTAINS one. Get some 2V5 voltage reference (because LM35 output is generally in the range of 0V to 1V).

the ADC and Microcontlr both are connected on a development board. the ICs get 5v from the supply. the Vref of ADC is getting 2.5 volts ,i tested with the oscilloscope

 

[FvM]

You skipped some elementary test steps, or at least didn't mention them.
- verify the correct design and operation of the uP to ADC interface
- apply a variable voltage to the ADC0804 input and check the ADC reading
- connect the LM35. If readings are not plausible, check it against the voltage measured at the ADC input