Good morning,
I was reading about the LM35 and saw that it does not work under the terminal 4V + Vs therefore believe
that the configuration that I mentioned above, putting the LM35 + Vs to 2.5 volts should not be correct!
The friend advised me Ericgibbs: "Use of a reference voltage of +2.5 to adjust itself to a conversion
ADC, 8 bit "
I ask: How? I change the hardware or software? and how to change?
I appreciate any help!
Cabral
hi,
You are correct that the LM35 requires 4V minimum, I use +5V.
The Vref I explained in my previous posts was for the +Vref pin of the PIC.
Get a 2.5V ref ic and connect the 2.5V output to the +Vref of the PIC.
This will set the PIC's adc conversion so that for a 2.5V input voltage onto the adc inputs, it will give a conversion value of 1023 decimal [3FFh]
Connect the LM35 Vs to +5V and the LM35 output to an adc input pin on the PIC.
So if the temperature is say, 100Cdeg, the 1,0V output from the LM35 will give a conversion value of [1.0V/2.5Vref] * 1023 = 409
This value has to be multiplied within the program to make it equivalent to 100Cdeg.
I prefer to use the PIC's internal +Vref [5v] and use an amplifier with a gain of five.
This means the output from the LM35 at 100Cdeg = 5V, so the adc converts this to 1023, the maximum possible value.
Do you understand this OK.?