tmp36

Other Hardware Sensors
1

hi all.
i have i reading to analog input A0 of tmp36 sensor,

every 4000 ms ,

the values i get in a room temperature are between 6 to 11 , and changing all the time.

warming the sensor with fingers does not change values .

should i consider this as faulty sensor ? or faulty input (tried to change amongs several inputs).

i use mega2560 .

(tripeled check gnd , 5v , and output legs from sensor)

thanks

oded.

2

If you have a DMM, you could measure the output voltage of the sensor.

25 degrees C should be 750mV between output and ground.

Leo..

3

Verify that you have the pins of the tmp36 wired correctly.

4

checked voltage at 27 celsius, it was about 400 mv.

input voltage was about 4.9 v.

so

that means the unit is faulty?

could be that by soldering the legs to 3 long wires i ruined the sensor?

thanks

5

The TMP36 has a 500mV offset, 10mV/C, so 400mV is 10 degrees BELOW ZERO.

Did you use a cap across the sensor, as in figure24/page10 of the datasheet.
If not, the sensor could oscillate and give false readings.
Leo..

6

hi.

i am testing the tmp36 sensor.

after bridigng the v+ with 0.1 m f capacitor , and managed to stabilize the fluctuations of results, i still

face the low output voltage over the analog pin A0.

the maximum was 90 in room temp of about 27 deg.

normally i should get 750 accotding to data sheet.(in 25 celsius)

result after calculation it over the 1024 scale are then very low temp and not real.

this is second unit i have , which i bought from 2 different shops, so i presum they are not faulty.

any idea as to my low input values ?

thanks.

one other thing i will try is to pull down all floating pins over the mega board.

do you think its going to change something ?

7

problem solved

osamuel:
one other thing i will try is to pull down all floating pins over the mega board.

do you think its going to change something ?

this seemed to have solved the problem

i had to ground 14 analog pins , which have very clearly reduced interferance , and raised the analog input reported values.

i have now reached my desired room temperature reading.

problem solved!

8

"any idea as to my low input values ?"

One idea, if the tmp36 is wired wrong, you don't get what you expect from it.

With the flat side of the tmp36 facing you (legs down), what do you have wired, left, center, and right pins?