Minty Boost -> USB -> Arduino Fail

[thealy]

So I built up my Minty Boost, loaded 2 Duracells, and tested the voltages using my prehistoric analog meter, and outside pins test just below 5 volts; ground to middle pins just under 2V. Before connecting the USB plug, I wired from it to the Vin and ground on my Duemilanove board and got a pwer LED lit. So far so good. I connected the USB plug and tested the same voltages.

Now using a standard USB to "D" style - which works fine from laptop to Arduino for both power and data - I connected the Minty boost to the Arduino. No power LED. Am I doing something stupid here? Cable issues?

Just as an additional data point, I decided to try and see if it would charge and old Google Android phone I have. The second I plugged it in, it went dead - blank. I thought I roasted it, but after removing the battery and re-inserting, it seems like it was not permanently damaged. Not sure what that might suggest.

I can send photos if you suspect I messed up the assembly.

Thanks, Terry

[adafruit_support_bill]

Post photos of the front & back of the board & we'll check the assembly. Since the voltages checked out fine, you probably have everything in the right location. Why it fails to power the Arduino is the mystery.

Check to make sure you are using fresh batteries. Weak cells can produce the right voltage, but the output will drop as soon as you put a load on it. Also, measure the voltage on the Arduino +5v pin.

[thealy]

Strangely, this turned out to be a polarity issue. I had cut a standard USB -> "D" USB ("D" like the one on the Arduino) to fit my project inside a Otter Box. When I was checking voltages and such, I decided to flip polarity for the hell of it and it immediately worked fine. I can't understand this - a standard cable will no work - but realized that a standard power connector is better that using USB for my project anyhow. If I can't un-solder the USB plug I will have to buy another kit and leave it off.