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Topic: TMP36 sensor getting very hot (Read 1 time) previous topic - next topic

mafabio

Hi there, I need an advice to read the value from a TMP36 temperature sensor.

I connected:
PIN1 to VCC (5V from Arduino UNO board, tried also with 3.3V)
PIN2 to A0 (analog input)
PIN3 to GND (GND of arduino UNO board)

No resistors or capacitors are connected to this section of the circuit.

Then I uploaded a simple sketch to read the value.
The read values (from serial monitor) are right, but the TMP36 gets very hot, so the values keep raising.
At about 100°C I unplagged the power in order to save the component.

Any ideas about why this behaviour?

Thanks in advance,
Fabio

Grumpy_Mike

Quote
No resistors or capacitors are connected to this section of the circuit.

The data sheet shows a capacitor across the supply on every single example. What makes you think you don't need one? It is probbly oscillating.

mafabio

I'm sorry but I'm a novice in electronics.
I'll try adding it, and let you know.

Thanks

Grumpy_Mike

Also check you have the power and ground right, that diagram in the data sheet is looking at the pins.

mafabio

Ok Mike, I've tried adding the capacitor (today I have only a 0,47uF), but nothing changed.
Power supply is the 3.3V supply from arduino board (tried reducing input voltage).
I also tried unplugging the analog output pin of the sensor (just to be sure that the problem is on power supply side..)

What else could be? A faulty sensor?

Thanks,
Fabio

Grumpy_Mike

Quote
I have only a 0,47uF

Might get away with that it s hard to tell.

Can you post a photo of your setup so we can see the connections.

Have you gone through this?
http://learn.adafruit.com/tmp36-temperature-sensor

mafabio

I've read that now, thanks.
I noticed that the V+ and GND pins are turned with respect to what is stated on the data sheet,
what do you think about that? Will I risk to burn the sensor in case I try to connect that way?

In case there's no problem buying another one, but it takes time to arrive..

I'm attaching my setup.

Grumpy_Mike

I would go with the tutorial. If the supply were swapped I would expect it to get hot.

mafabio

Damn datasheet.. now it works without getting hot!!
Thanks a lot for your help!

Fabio

be80be

#9
Dec 21, 2012, 01:32 am Last Edit: Dec 21, 2012, 01:35 am by be80be Reason: 1
You had VDD on the ground side it shows in your Picture it's some times misleading
how the pin are like the 2n7000 some show bottom up pin side and some show top  down

This data sheet has it right http://www.analog.com/static/imported-files/data_sheets/TMP35_36_37.pdf


mafabio

Yep.. You're right. I didn't realize that the view of the datasheet was reverse.
The view of the sample (3D) was clearer.

So it was my fault, not the datasheet.  :)

Thanks a lot again.

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