[crispy429]

Hi guys, just received my NO2C and assembled it yesterday, but when I connect it to the Arduino, the Arduino dies (I have it attached to computer and connected to TunerStudio). If I connect it a few pins at a time, it doesn't die until the +5V pin on the bottom of the NO2C contacts the Arduino. I've measured a 3Ω resistance across the +5v to GND, which seems strange to me... This is less than any resistor (though possibly not the resistor network) and larger than a short. I removed these 5 jumper pins to see if there was a bridge underneath before discovering that the plastic slides up (so checked the other jumpers as well). My current thought is that this is low enough for the NO2C to short the +5v and take power away from the Arduino and shuts it off.

I've tried supplying +12v to the NO2C and +5v to the Arduino through USB and DC, same behavior. I've checked for shorts and can't find anything obvious or under the jumper plastic. Any ideas of what the problem might be or what I can try to rule some stuff out?

Thanks,
~Chris

[turboedge]

The two components circled in red are not the same and have been put in each others place. They need swapped around.

[crispy429]

Ok good catch, I swapped those out and it’s still doing the same… any more ideas?

[turboedge]

I don't see any other soldering issues. other than the ground and 5v pins not being installed. Also the power regulator (the one by itself) will probably go into thermal shutdown with its tab removed like that. It needs to shed a fair amount of heat, but that's not the current issue. I'd suspect a diode in the wrong spot and/or incorrectly installed. Can we get some good top down pics?

[crispy429]

There's a weird thing going on with the two lower left diodes, are they connected in opposite directions? All numbers in the photo are resistance measured with the positive lead at the labeled resistance location. I noticed that on those bottom left diodes, the resistance is the same at the bottom left and top right of that set, which made me think they were connected and allowing flow through the same path, but the resistance is so similar to the other 'cross' direction that I can't think of a reason to have diodes organized this way.

EDIT: Understood about the power regulator. I thought it was an IGBT and read that you could carefully cut the tabs off with no issues and I'd like lots of clearance as it's going in a bike. I'll try some thermal paste and a tiny heat sink on it and see if that does the trick.

EDIT2: Looking at the part numbers of the diodes, I think I have D3 and D4 mixed up, I'll try swapping them.
EDIT3: Swapped them, no difference... Dang.

[crispy429]

Is there a schematic available for the PCB that I can use to check which pins should and shouldn’t be conducting?

Can anyone do me a favor and measure the resistance between +5v and GND on a working board? I feel like these shouldn’t be connected by such a small resistance, I get 3ohm on mine…

[crispy429]

All good! It was the USB cable not providing enough power and there would be a voltage drop momentarily. Works fine when plugged into the wall or on 12V power

[turboedge]

USB should provide enough power, something odd is happening there. If you are looking for schematics check wtmtronics.com/help you should find what you need there.

[crispy429]

Sorry, I should clarify - the USB cable setup I was using was insufficient. I have an extension from the computer to the front of my desk and a splitter with some keyboard/mouse dongles plugged in drawing some power, so the power was insufficient. I checked that this might be the cause back when the IGBT and power supply were swapped and it made no difference, but now with those corrected, plugging the Arduino directly to a USB port on the computer with nothing else drawing power works just fine.

Thanks!
~Chris