I managed to burn out a TMP36 temperature sensor chip. This happened Thursday. Here's the story.
In an attempt to both wake up my brain cells and learn something useful, I recently bought this Arduino start up kit from Amazon. I've been doing the examples without problems until I got to a circuit that used a photo resistor to control the brightness of an LED (using PWM) such that the brighter the ambient light, the brighter the LED. I built up the circuit as described in the guide, and my circuit worked, kind of. The LED got darker as the ambient light got brighter. I checked out the schematic and it looked to be correct. It uses a voltage divider to convert the changing resistance of the photo resistor to voltage. So then I looked more closely at the circuit guide, which which tells what electrical components are needed and how to wire them up in the prototype breadboard. Lo and behold, it had photo resistor on the wrong side of the voltage divider. Putting it on the correct side fixed the problem. I thought, "what lousy quality control" and then moved on. I should have remembered the lesson.
The very next circuit is the temperature sensor circuit. It's a very simple circuit where the +5 from the Arduino card is connected to the +5 pin of the T36, the GND of the card is connected to the TMP36 GND pin and the sensor TMP36 sensor pin is connected to an analog sensor pin. I verified that the circuit guide accurately reflected the schematic (it did) and hooked it up. However, when I powered up the Arduino board, the indicated temperatures were about 20F less than the ambient temperature. I lightly pinched the TMP36 to increase its heat and the indicated temperatures rose over time, but were still too low. The TMP36 chip is +-2% accurate, so I new that I either had a bad chip or something was wrong with the circuit. I found the data sheet and discovered that the manual from the kit had the +5 and GND pins reversed. At least it was consistent in this.
So I unpowered the board, reversed the TMP36 and powered the board back up. Success, the temperatures were now correct. I did something else for about 5 min and everything was still working. So off I went for a shower. When I came back, the indicated temps were in the 450F range, I could smell something burning and the TMP36 chip was way too hot to touch. I verified that the +5V of the Arduino was still putting out 5V, so all I can think is that the TMP36 chip has shorted. I'll be buying a new TMP36 chip just to satisfy my curiosity.
Sorry for the long post, but mainly I want to warn anybody buying this kit to verify everything in the manual before applying power to your board. I will be for the rest of the example circuits and any circuits I create in the future.
Edit: Here is the Guidebook in question. The pertinent circuits are #6 and #7. I looked at the pdf from the website and it still has the problem. So beware of the contents of this Guidebook. I will say that the presentation is great and this would be a top-flight product if the information was reliable.
