Electronics > Beginners
Temperature indicator circuit with LEDs
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Zero999:

--- Quote from: dazz on August 20, 2018, 09:23:31 am ---Oh, one more question, please. How well will that TMP36 (TO-92) work to measure the IC temp? The plan is to glue it to the chip, or perhaps to the bottom of the board since the bottom ground layer acts as a heatsink. I mean, I'm building a circuit based on a sensor but I don't even know if there are better solutions for that purpose

--- End quote ---
It'll just measure the case temperature. The actual temperature of the chip will be higher and will depend on how much power it's dissipating, he heatsink and ambient temperature.

Why do you want to do this? The IC has over-temperature protection built-in. Make sure the heatsink is good enough and it should be fine. The only thing that might be required in extreme cases is a fan, which could only be turned on when it's hot, which will be when the volume level is so high, it will drown out the fan noise.
dazz:

--- Quote from: Hero999 on August 20, 2018, 11:27:30 am ---It'll just measure the case temperature. The actual temperature of the chip will be higher and will depend on how much power it's dissipating, he heatsink and ambient temperature.

Why do you want to do this? The IC has over-temperature protection built-in. Make sure the heatsink is good enough and it should be fine. The only thing that might be required in extreme cases is a fan, which could only be turned on when it's hot, which will be when the volume level is so high, it will drown out the fan noise.

--- End quote ---

Well, I started a thread a few days ago because I was concerned about the board's heat dissipation capabilities. I know there's thermal protection implemented in the chip, but the hotter runs, the more it distorts, so I thought I could try adding a heatsink and measuring the temperature to see if that helps and how much. Of course the LED indicator would only give limited information about the chip temp (between 40ºC and 60º, 60ºC and 80ºC, and above 80ºC) but I thought it would be cool to have something to warn me if temps are getting too high if, for example, I was to load it with 4ohms and feed it 24V while playing with distortion effects, hence pushing the output power above "normal operating" conditions. 
james_s:
For an actual useful measurement, your finger will probably be more precise than a few LEDs. Generally I figure if I can't touch it for at least a second or two without burning my finger then it's too hot.
dazz:
Ahh, this is a massive fail. As Hero999 suggested, it's too temperature sensitive. I had the circuit breadboarded and working nicely, but as soon as I heated it up with an electric heater, one of those that blow hot air, the amps shooted up by a lot. The red LED went from 150mA to almost 2A  :palm: :-DD. I wasn't measuring the current through the yellow LED, but I could tell it was about to blow up.

Oh well, off to shop an Arduino I guess  |O
Zero999:

--- Quote from: dazz on August 20, 2018, 06:16:05 pm ---Ahh, this is a massive fail. As Hero999 suggested, it's too temperature sensitive. I had the circuit breadboarded and working nicely, but as soon as I heated it up with an electric heater, one of those that blow hot air, the amps shooted up by a lot. The red LED went from 150mA to almost 2A  :palm: :-DD. I wasn't measuring the current through the yellow LED, but I could tell it was about to blow up.

Oh well, off to shop an Arduino I guess  |O

--- End quote ---
Which circuit did you build? None of the circuits you've posted in this thread should fail like that.
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