Focshield v2.0.4 current sense challenges - ina240

Hey everyone,

I’ve been trying to get current sensing working with the focshield v2.0.4 + as5048a + gm3506 gimbal motor.
I haven’t been able to get it working - but have been getting an error during the alignment process - “CS: Err align B”.
I started digging around a bit and have come to discover that the INA240A2 for phase A is working as expected - but the INA240A2 for phase B is not working as expected (e.g. I believe it should output ~1.6V when there is no Vdiff across IN+ and IN- , but it tends to read somewhere between 0.8-1.2V instead of ~1.6). It also doesn’t appear to respond properly when there is a Vdiff (e.g. its output doesn’t change when there is ~1.2-3mv across IN+ and IN-)
Is this a simple case of the INA240A2 for phase B being broken?

If it is broken, would y’all recommend I upgrade to the Focshield v3?

Thanks in advance!

Hi @eplamers,

It could be, it seems reasonable to consider it being out of order.
The voltage of the 0 Vdiff should be the same as the half of the 3.3V range so around 1.6V. And even if there is some offset, say its at 1.5V or 1.7V, that is fine. But it should be static, it should not vary between 0.8 and 1.2V.

The change of 3mV should result in 50*3 = 150mV (0.15V) at the output of the ina240a2. So if it doesn’t change the chances are that there is something wrong.
Does the phase A sensor respond as expected to these types of tests?

They both (v3 or v2) will be able to do the job for you in your setup, provided that they function correctly :D.
So which ever one you can get hold of will do. :smiley:

Hey @Antun_Skuric

Yes that is correct, the phase A sensor is responding as expected!
Thanks for the feedback, this is my first time working with the INA240 so I wanted to make sure I wasn’t missing something.