TMP36 sensor gets extremely hot

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jvcalin
 
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TMP36 sensor gets extremely hot

Post by jvcalin »

Hey all,

I'm extremely new to this so forgive me if this has already been posted. I did a search but didn't see it.

Not really a question but just wanted to post a tip about working with the TMP36 sensor. I thought I followed the wiring diagram but when I connected the power the sensor got extremely hot! Like burn your finger hot! It turns out that the Gnd and 5V pins were switched. So if that happens to you, switch the two pins... The sensor isn't supposed to get hot.

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adafruit_support_mike
 
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Re: TMP36 sensor gets extremely hot

Post by adafruit_support_mike »

Most microchips have 'input protection diodes' built into the part of the circuit that connects to the pins. They're basically diodes connected backwards to make sure the input never goes more than 0.6v volt below GND or above VCC. Bad Things Can Happen if the inputs go too far past the voltages the chip expects.

In your case, plugging the TMP36 in backwards meant the diodes were pointing the right way, and current started flowng through them. Diodes start to conduct when the forward voltage is about 0.6v, and for every 60mV above that, ten times as much current can flow through. At 1.8v, the current will be somewhere around an amp, and at 2.5v it would be about 10 amps if the chip hadn't already burned up by then.

Heating a chip up like that can damage it, and at very least can mess with a temperature sensor's calibration. If the chip still works for you, that's fantastic. If you find that its accuracy is off, that's probably a side effect of overheating.

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jvcalin
 
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Re: TMP36 sensor gets extremely hot

Post by jvcalin »

Thanks!

I unplugged the power as soon as it burned my finger (got a blister on my thumb). I was pinching it to try and get it to warm up not knowing it was already super hot... it still works thankfully, though the sensor is pretty inexpensive, so it doesn't really matter.

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modeller
 
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Re: TMP36 sensor gets extremely hot

Post by modeller »

jvcalin wrote: I unplugged the power as soon as it burned my finger (got a blister on my thumb). I was pinching it to try and get it to warm up not knowing it was already super hot... it still works thankfully, though the sensor is pretty inexpensive, so it doesn't really matter.
Buy another one and use it to measure the temperature of the other one connected backwards!

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john444
 
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Re: TMP36 sensor gets extremely hot

Post by john444 »

Modeller,

I am guessing that you think your comment is funny.
However, when people make remarks in the forum that are not really helpful to the person asking for guidance, it discourages them (and others) from asking in the future.

John444

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modeller
 
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Re: TMP36 sensor gets extremely hot

Post by modeller »

john444 wrote:Modeller,

I am guessing that you think your comment is funny.
However, when people make remarks in the forum that are not really helpful to the person asking for guidance, it discourages them (and others) from asking in the future.

John444
John, can I PM you?

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adafruit_support_mike
 
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Re: TMP36 sensor gets extremely hot

Post by adafruit_support_mike »

jvcalin wrote:I unplugged the power as soon as it burned my finger (got a blister on my thumb).
Yikes!

Considering the fact that you've been a good sport about it, I just bought you an honorary Magic Smoke Skill Badge. I'm stretching the rules a little.. technically the smoke is supposed to come out of the component, not out of you.. but we've decided this deserves a pass. ;-)

Send a note to support@adafruit.com with a link to this thread, and the folks in shipping will do their magic.

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john444
 
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Re: TMP36 sensor gets extremely hot

Post by john444 »

@Modeller,
You may PM me if the service is working.
Although it has been disabled for a while now.
Or, just e-mail me directly @ banned
should be all run together.
(The nasty spammers make you send messages in code.)

John444
Last edited by john444 on Thu Feb 28, 2013 2:22 pm, edited 1 time in total.

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modeller
 
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Re: TMP36 sensor gets extremely hot

Post by modeller »

john444 wrote: Or, just e-mail me directly @ banned
No, I specifically asked if I could PM you. I never give out my email address on forums, and you shouldn't either. Nobody should. Giving out email addresses on forums is an anachronism. That's why I x'ed out your email address in this response. You should edit your post to remove it, even as you tried to make it harder to use.
(The nasty spammers make you send messages in code.)
Yes, indeed, the nasty spammers. You know, I have a forum of my own (completely different subject), and I don't have any spammers. How about that? Look at the who's online list here. I'm looking at it right now and there's spammers registered, like this one -

elagmaBiola

I spotted it just by the name alone. Interesting you might think - How did I do that?

I've been involved with owning and running forums for years, and there's never, ever, ever, been a time where we had to disable PMs because of spammers. PMs are the defacto means of communicating privately with other members, and should have/would have been used in this case of our back and forth. I don't know why the Admins here aren't doing anything to stop the spammers. I've looked again at the registration page and what they have there (or don't have) is the problem. If they would take advantage of my experience (I've offered to help before) they might be able to stop more of the spammers. Somebody is listening to me because when I pointed out in another post that the birhtday list was being used by the spammers to show their names, somebody disabled it. They didn't thank me for the advice though.

But that isn't enough. The spammers aren't interested in PMs, they are interested in putting advertising links in their profile and signature. If you don't believe me, look at a spammer's profile. I don't use phpBB (I use SMF) but I went to their help pages and it took me less than 5 minutes to find the information they need here to help reduce the spammers.

Hint: For starters, the CAPTCHA is almost totally useless these days.

Like I said, if they want me to help, all they have to do is ask.

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john444
 
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Re: TMP36 sensor gets extremely hot

Post by john444 »

@ modeller,
modeller wrote:No, I specifically asked if I could PM you
You must have missed:
john444 wrote:You may PM me if the service is working.

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jvcalin
 
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Re: TMP36 sensor gets extremely hot

Post by jvcalin »

mstone,

Ooh, thanks! My very first badge! :)

I figured I was bound to ruin a few components at first... and I'm sure this won't be my last mishap. Though I'm sure to check for heat more often though. :D

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adafruit_support_mike
 
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Re: TMP36 sensor gets extremely hot

Post by adafruit_support_mike »

Just wait.. you'll get to the point where you can identify overheating components by smell. Transistors and ICs all use the same epoxy, but resistors, diodes, and LEDs all have their own bouquet. Capacitors are easiest to spot though.. just look for the charred and smoking hole. ;-)

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adafruit_support_rick
 
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Re: TMP36 sensor gets extremely hot

Post by adafruit_support_rick »

I'm particularly fond of banned Candles, myself. They typically involve some very wrong voltages.

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treatablebum
 
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Re: TMP36 sensor gets extremely hot

Post by treatablebum »

Had the same heat problem with TMP36 ... couldn't find pinouts easily on site; manufacturer's site has the Pwr and Gnd reversed. :twisted:
Knew enough to cease and desist within seconds while testing and search the support forum a little more. :D
Works great now as an inside temp along with an outside temp/humidity sensor [AM2302 (DHT22)] using heat index code.

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spork99
 
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Re: TMP36 sensor gets extremely hot

Post by spork99 »

The DS18B20 digital temp sensors do the same thing if you reverse the signal and ground wires. Like the OP, I burned a nice hole in my finger grabbing onto it while trying to figure out what was going on. I also said a lot of bad words. It still works though.

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