Hey All,
I just got two new UNO SMD R2 from sparkfun. I discovered a very bad bug on my boards. It seems that something is allowing 5V on to the 3.3V power rail (might have blown a nice new IMU too... 
This is observed on both boards so it is not a fluke. Can anyone else confirm this on their SMD R2?
TL::DR 5V showing up on 3.3V pin.
Thanks,
Chris
On my Ard. Uno the pin 3V3, without any loads, has 3,31 Volts...
Is this with USB power or power jack?
Have you checked the voltage from your USB/what's coming from the DC power supply.
This happens with both USB and external DC power jack. I'm having some issues troubleshooting as the UNO SMD R2 eagle files are not available, only the R1 is posted right now. 5V DC bus voltage is 4.97, 3.3V bus is 4.93 unfortunately.
Anyone knows what's the difference between 'SMD' and 'SMD R2'?
As far as I know:
Uno: Original board
Uno R2/Uno SMD: ICSP connector and pulldown resistor
Uno SMD R2: ???????????
Both of those circuits show the 3v3 regulator is used with USB or External power.
Don't suppose there is anything plugged in.
I would also check on the connector where the 5v and 3.3v pins are right next to each other.
I have an R2 version and it seems to be fine.
I can post some pics if you need.
Mark
Sorry for the long delay in response, went on vacation.
Anywho: this is not an UNO R2, this is an UNO SMD R2. I've posted pictures below:
Has anyone ever seen these before? I'm just looking for a parts list or schematic. I think there might be a 5.5v regulator in place of the 3.3v regulator as the two busses are not shorted together (testing with my meter).
I think there might be a 5.5v regulator in place of the 3.3v regulator as the two busses are not shorted together (testing with my meter).
That would be a rather rude error on arduino's part!
I would contact sparkfun's customer service, they are pretty good about rectifying such problems if indeed it was an assembly error.
Lefty
Gents
I have highlighted the regulators on the UNO picture...yes its not a R2 but my R2 has the bits in the same place as the picture.
The 5v reg has
07AB
N06
markings
The3v3 has
LPFL
on it.
hope this helps.
Mark
I've just purchased an Uno smd version. I found that the 3.3v pin is actually at 5.0v, even with a load on it.
I had a closer look at the 3.3v regulator (LP2985) and it's marked "LOUA", same as the one in the post by creeg2 above.
According to the datasheet at national semiconductor (http://www.national.com/ds/LP/LP2985.pdf), this is a 5.0v regulator, which explains why I'm not seeing 3.3v.
I've emailed the vendor where I purchased it, we'll see what can be done about it.
Is this the design in question (realizing the parts issue appears to be solved...)
No, I guess not, that was not the SMD design. Thought I had it for reference.
