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Topic: How to measure chip (or other component) temperature? (Read 1 time) previous topic - next topic

afremont

#5
Mar 08, 2013, 07:36 pm Last Edit: Mar 08, 2013, 07:50 pm by afremont Reason: 1
Thermal imaging is probably the best way I can think of, but it really costs allot of money for an imager.  Guess that's probably why I don't have one.  Next is my your finger. ;)  I have a non-contact thingy, but mine includes too much surrounding area for parts like resistors.  Even held really close, I don't really trust it on small parts.  Gotta watch out for shiney parts too.  IR sensors seem to have trouble with really glossy surfaces like chrome or gloss black harley paint on the oil tank.
Experience, it's what you get when you were expecting something else.

Docedison

#6
Mar 08, 2013, 07:43 pm Last Edit: Mar 08, 2013, 07:53 pm by Docedison Reason: 1
Jim, A little dab of "Elephant Snot" as it is sometimes "fondly" called in Southern California is your best bet. Inexpensive heatsink compound. The thread linked was someone complaining that he didn't do his homework right... or didn't have the tools to do it right... It's all calculable but like writing code requires some training... first. When, without planning or at least writing down the basic requirements first... and starts "throwing parts" at an idea... one frequently ends up complaining about abused parts...
It's Too Hot To Touch, What Do I Do.. ? How many times have you read that here in this group alone?
If you are desiring of making some kind of thermal monitor... either write up your thoughts on preferred method here or PM me... either way I'd be happy to help.
The comment about the math being able to calculate the die temp was correct but I also know that the cooler a device is in operation the longer it will live, so anything uncomfortable to the fingers should be investigated... Probably the best thing is the aforementioned non-contact IR thermometers they can be had (Good quality ones) for less than $25.. on Ebay I didn't read all of it carefully, Edit RKJ

Bob
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

JimboZA

Quote
Thermal imaging is probably the best way I can think of, but it really costs money for an imager.  Next is my finger


.... and in between is my trusty Fluke.
Roy from ITCrowd: Have you tried turning it off an on again?
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

JimboZA

Quote
If you are desiring of making some kind of thermal monitor...I'd be happy to help


Thanks Bob, but no it's really just curiosity, wondering how useful my Fluke's thermocouple would be in monitoring temp of a component.

Roy from ITCrowd: Have you tried turning it off an on again?
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

oric_dan

Heat kills. There are some guys who think whatever it says, up to thermal shutdown
[eg, 175 degC] is ok, but I don't like my electronics running too hot, or failing prematurely.
So I use the Little Pinkie Test = if it's too hot to hold my little finger on the chip, then it's
too hot. And some redesign should be done. I also have a non-contact IR-Thermometer like Bob.

As Erdin indicated on that other thread, the L293s are bipolar technology, and not MOSFETs,
so there tends to be a collector-emitter drop of upwards to a couple of volts in those parts
[because the output stages have darlington pullup and pulldown ckts], and that times the load
current gives the power dissipation, Pd = Vdrop * Iload. Newer MOSFET h-bridges are much
better.

http://idmax.free.fr/Aide/Stepper/l293.pdf

Also, you might look at the TI 754410 as a drop-in replacement for the L293D. 754410 can go
to 1-Amp load vs 600 mA for the 293.

BTW, one way to tell if an L293 is too hot is, the chip will literally blow up and catch fire. This
actually happened to me once. Not just magic smoke, but the plastic end blew off, and flames
actually came out. So much for thermal shutdown. A mini Boeing 787.

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