I was thrilled to get my hands on a FetaDuino from Rocket Brand Studios. Only now I think I have damaged it.
I was wiring in a swich on the GPIO pins. I had the switch wired to a 3-pin header, with the switch common going to the signal line, normally connected (NC) going to +5V, and normally open (NO) going to GND.
Com <-> Signal
NC <-> +5V
NO <-> GND
Unfortunately, while troubleshooting something else, I accidently inverted the switches header when connecting it. So that shorted the NC/+5V line to the NO/GND line. The Feta blanked and reset after I removed the switch header, which was pretty close to immediately.
The result wasn't immediately catastrophic, for which I give Chris and Patrick (the board's designers) high credit. The board seems to operate fine, but the contrast on the LCD is barely visible at best, even when using the provided trim pot. It works fine when powered from the USB port via my FTDI Friend.
I suspected the voltage regulators had been damaged by the short, and a quick test confirmed it. the 3.3V regulator is only putting out about 2V and the 5V regulator is putting out about 3V.
SO...
If you have a FetaDuino, be careful not to cross the streams!
Now I'm wondering if I should order replacement voltage regulators and try my hand at SMD repair. Sounds kinda hard.
Sorry to hear
Sorry to hear that…
Accidents happen all the time. Been there, done that. That’s why I stick by using TH components, it’s easy to replace a burnt part. Anyway, this can happen to any board, some boards have protection to accidental battery polarity reversal (at the expense of a little voltage drop), but unless the board has polarized connectors for each “3 pin” group you have to be extremely careful not to reverse anything. And when you’re experimenting with a breadboard, well, you’re always in danger of something pop-ing…
I wish you good luck replacing the v-regs!
Yeah, lesson learned. I
Yeah, lesson learned. I should have been more careful.
Replacing the regulators will have to wait. I need to get this project done. I’ve got the board running great now with an external voltage regulator. Results will be posted soon.
(Smile)
I’ll get a couple new regs in the mail for you quite soon, sir.
Because… Here at Rocket Brand Studios, we understand that mistakes like this will happen from time to time and our #1 goal is to get folks up and running. Fried a couple cheap parts? We got you covered, it’s on the house.
TING!!!
Wow! Thanks, Chris. No
Wow! Thanks, Chris.
No rush, since I’ve got it working for now with an external regulator. That’ll get me through the current project.
Do you believe anything else would have been damaged by shorting GND and V+ on the GPIO pins? AFAIK, the board is working fine other than the regulators.
This will be my first SMD soldering job. Is this sort of repair even possible without a solder reflow station? Hopefully I won’t fry the whole board trying to replace the two regulators!
Not really SMD…
Yup, that’s what did it. Pretty simply actually, and (I think) would happen with any volt reg --by shorting 'em and you are “requesting” a metric crap-load of current. The little reg tries to keep up and give you the current you ask for, and smokes itself in the process. No biggie, I buy volt regs in rolls of 100 or 500. 
In terms of SMD work, it isn’t really. In the grand scheme of SMD parts, those volt regs are huge. Big legs, big sink, plenty of room to get an regular iron in there. I would go after the heat sink first, hit it with a little flux and then put a big blob of solder on your iron. “Wipe” this big blob all over the heatsink until it’s solder has melted, then gently pry/pull up the heat sink (yes, bending the other legs) just enough so the solder won’t grab again when it cools.
Now, wipe your iron, flux the legs and re-apply a big blob of solder on the iron. Wipe this blob back and forth across the 3 remaining legs while gently tugging on the heat sink with a pair of needle-nose. When the solder around the legs is all liquified, the whole thing will lift.
Tidy up all the now-exposed pads with a little solder-braid, and you are all ready to solder in the new parts. Trust me, this whole “wipe a big blob of solder trick” works so much better than trying to go after it with braid. --The whole thing will be a piece of cake, no worries. Oh, and let the blob do the work --there is no need to really “pull or pry” any of the parts, when the solder has been properly melted, the part will come.
By supporting our community
By supporting our community I bought 2 of them as well but I haven’t really used them since yet. Until last night I took them out from dust and do some test and I guess I did the same mistake as well.
The regulator become very hot very soon when I connect the battery on. Thru FTDI was fine thou. I am not sure if I made same mistake. If so, I do have few SMD regulators with me to replace them. Just wanna make sure.
I’m using a 7.2V NiMH
I’m using a 7.2V NiMH battery, and my fried regulators don’t get hot. I’m currently using an external regulator to get a clean 5V when I’m operating from battery.
If your regulators are getting hot, it sounds like something is still shorted. What sort of battery are you using? If it is really high voltage (over 12V), that might explain the heat.
Try using an external 5V regulator or power supply on the 5V and GND pins of the 5-pin bent header. This should bypass your internal regulators.
I was using 7.4 lipo and 6V
I was using 7.4 lipo and 6V 4xAA, both are hot when connected. Maybe will take closer look tonight.
