Only thing smoking is IC3!


 
M

MattNCSU

New member
So I completed my first HeaterMeter (4.0) and it runs perfectly on 5V power from the Raspberry Pi. After getting everything setup, I decided to try out the 12V plug. Disconnecting the 5V cable and plugging in 12V from an old DSL modem brick (12V, 1.2A, transformer type-i.e. heavy) I started getting smoke from IC3 after a few seconds. I double checked and IC3 is installed in the correct orientation.

I unplugged the 12V and let it cool down and tried again on 5V, everything continued to work so I don't think I caused any damage. Ironically enough, the hottest part of IC3 was next to the "sizzle" graphics on the Weber image. While on 12V, the display powered up and displayed the ambient temp from FOOD3 so it would seem that the DC/DC converter is working but I'm afraid to leave it powered up long enough to measure any voltages.

A visual inspection doesn't immediately reveal any bad solder connections or components installed incorrectly. Any ideas where and what to start probing with my multimeter?

A few photos: https://picasaweb.google.com/mattncsu03/Heatermeter?authuser=0&authkey=Gv1sRgCKblkbaal_KtNQ&feat=directlink

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(prior to setting probe coefficient)
 
A quick look over of your board I don't see anything immediately wrong. You should try plugging in the 12V without the Pi connected to see if it still gets hot and narrow down the problem. If it doesn't, try adding the 3.3V regulator (just drop it into the holes and hold it with your finger, no need to solder it). If everything is still fine, that means there's something happening between the power regulator and the Pi. Not sure where to go from there.
 
What is the power supply is supplying far more than 12V? I've found to be the case on more than a few 12V supplies I've tested.
 
Steve, you were right. It didn't occur to me at the time why I was getting no-load volt readings around .1 VDC on my multimeter. Just assumed it was because there was no load. Turns out, in my excitement for finding a 12V wall wart in my box of obsolete electronics, I failed to notice this was a 12VAC supply. Have it running on 12VDC and everything seems to be working normally. Thanks!
 
Well that's a new one, now I know what happens when you plug 12VAC into a HeaterMeter. Happy to hear it didn't fry anything and you got it working.
 
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