Main Site Documentation

Analog Input Port


#1

Hi Guys!

I inverted the position of LM35 (temperature sensor) in the analog port and can no longer read through them.
What can be?

Thank in Advance.


#2

IF you reversed VCC and ground you most likely destroyed the chip.


#3

Mike,

I reversed the LM35, not GND and VCC, do you understand me? Do you think I destroyed my FEZ Panda ?

Thanks


#4

obviously not, so its best if you detail exactly what your device is (what package size) and what you did as “reversed” or “inverted” means little without more context. Specifically please tell us what pins you had connected where, and what you did when you reversed it.


#5

Ok Brett.

I will try…

Go to this link http://www.national.com/ds/LM/LM35.pdf , go to page number 2, look for the TO-92, this is my model of LM35, OK ?

I inverted the +VS to GND, was positive (+) to GND and negative (-) to +VS of the LM35.

Do you understand ?

After this, I can’t read from An0, or An1… to An5 (A0 to A5), I get values around the 60
to 70, ONLY.


#6

So if all you did was reverse the + and - lines and the data pin was still connected to the same analog in pin on the Fez, then you did what Mike pointed out. Most likely you’ve trashed your LM35. But to be perfectly clear you need to say “I connected the 5v or 3v3 line from the Fez to the GND connection on the LM35, and the GND line on the Fez to the +VS line on the LM35”. That is clear, precise, and tells us exactly what we need to know.

Disconnect the LM35 and read voltages supplied to the analog pins through a potentiometer, you’ll probably find this works fine. This means Fez is fine and no concern.

What is the “test” you’re using when you get values between 60 and 70 only? Connected to what? (I hope you can see that this small piece of information needs more context to help troubleshoot things)


#7

OK Brett, you was very clear to explain the topic.

I got the values (60 - 70) when I read the LM35 in correct pin… before I have broken my FEZ I got (260 - 270) - maybe 28ºC.

Now I don’t have the potentiometer to measure the voltage.


#8

Just connect the analog pin to ground and see if you get around 0. Then connect to 3.3V and see if the reading is high. That would at least indicate that you can stop worrying.


#9

Thank you Lurch… after my work schedule, I gonna get the values!

:slight_smile:


#10

Hi Lurch,

I connected the GND and 3V3 to Analog Input and I got the values, GND -> 0 and 3V3 about of 1020,
1023, is right?

Thank you.


#11

yes those numbers are correct.

So now throw away that LM and get another. And this time connect them the right way around !


#12

Ok lol!

I gonna throw my LM35 into the garbage this weekend and I’ll post the result again…