Power Profiler Kit II : reverse current and and disable leds

[BramPeeters]

Hi, 

I just got a power profiler kit II and I want to use it in an battery based application, where there is also the possibility that current will flow in the opposite direction. Eg when an usb cable is plugged in to transmit updates).

What will happen in case such a reverse current goes through the profiler ? Possibilities I can thing of, in order from good to bad:

- it will nicely show negative currents (one can dream right)

-  it will just show 0 but let the reverse current pass,

- it blocks reverse currents

- you will get magic smoke 

- ....

The magic smoke would be bad, I can foresee a bypass switch but it is a given that I am going to forget to toggle it in the heat of the moment. A diode has too much voltage drop, maybe an ideal diode would do the trick ? Anyone already tried something like that ?  

And is there a way to disable the led lightshow that I am missing ? I can't find it in the options. I also tried looking at the github page to see if the source code for the firmware is there to make a build without the led. but I only see the hex image. If there is no other way i will desolder the leds but I am hoping I am missing a less drastic solution. (imho blinking is for things that need someones attention, like a firetruck or something, nor for steady state. And even those should be discrete, not blinding floodlights ;p .).

Apart from that it seems like a nice addition to the toolbox

[PaKa]

The magic smoke is very likely and negative current is clearly listed as not supported for the PPK2, it's not designed to support it.

The source code is closed source so if you don't want the light then duct tape may be a less intrusive option than desoldering components.

[BramPeeters]

I imagine it is mostly for battery fed applications that you will use this kind of tool, so I am probably not the only one running into the issue. What I did for now as a workaround was replace the battery with a bench supply with a voltage high enough so the there will not be any charging going on.

But looking at the schematic I think it might be just fine with reverse currents for battery charging purposes (not for something that eg pushes a  fixed 1A current through it) . The input/output connection will be there (maybe through a 1K resister, but that is not a problem except that it wont charge very well :) ). And the signal amplification will not work but i am hoping nothing will be bbq'ed there. You just get a 0 on the signal to the processor. 

But a confirmation from someone a bit more knowledgeable than me on the electronics side would be nice :).

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And the duct tape is not very practical unless you wrap it up like an xmas present as he light is coming from everywhere.

I already removed the standard lightbars  and put a single small led over the green trace/3v3 to  I get some gentle feedback when the board has power, but as soon as it connects with the app it is 'visually silent'. 

Removing the mosfets  Q1b, Q15a, A15b would be another option and probably a lot easier to get of than the ledbars, but then you will not be able to foresee any feedback. 

Removing only Q1b, Q15a and leaving Q15B will give you the bright green feedback but nothing after connecting, and maybe combine this with a higher resistor value on R94/R97 to turn down the intensity of the led. That would probably be a nice workaround too and you still have the lightbars should you even feel the need to go to disco mode again :) 

[PaKa]

So the hardware guide specifically says no reverse current so you will not get a statement that is OK to do.

Modifying the board is of course up to you but it does void any warranties of course.