Hello, I am using the Mini Carrier Board PRO v2 for a boat, but when measuring current from Mission Planner, the measurement gets stuck at one value and does not want to go up to its actual measurement. For example, when I accelerate my motor, I read up to 9.7A in Mission Planner, but I am at 25A when measuring with other equipment. I am using the parameters indicated by the manufacturer. Does anyone have any idea what might be happening?
Set LOG_DISARMED,1 and do the test again please.
Provide the .bin log file that is produced.
Remember to set LOG_DISARMED,0 later when we’ve solved the issue.
What was the voltage doing while the current was increasing?
Here is the file, when the motor is on, the voltage decrees a little but when it’s stop it gets to its normal voltage.
Thank you very much
The voltage and current match behaviours given the throttle input in this log.
The throttle output goes very quickly to maximum (or near to maximum) and current follows this. It would be handy to see a gradual increase in throttle to see if current tops out at some point.
Keep in mind the current scale is showing +8.7 amps and can go all the way down to -12.41 - a difference of 21 amps.
I cant see a reason in parameters why there would be that offset, it’s like you’ve got the battery current sensor wired in one of the motor wires.
The battery positive and negative (and nothing else) should be connected to the large input pads of the power distribution board. All speed controllers and every other accessory should be connected to the smaller output pads on the sides of the power distribution board.
Can you show a picture or detailed diagram of how everything is wired up.
Just throwing something out there:
BATT_AMP_OFFSET 0.350000
BATT_AMP_PERVLT 35.798599
So, 35.8 a/v x 0.35v = 12.49a.
Would it be worth just setting the offset to 0?
Hi Allister, I was thinking about that too, but I concluded it’s not valid (so far).
The Kore carrier has an offset too: BATT_AMP_OFFSET,0.37
But this just improves the current calibration, so at idle you might see a 100mA or similar instead of a large value and resultant bad battery messages. It doesnt give us a 68.5 A/v x 0.37 = 25.345A offset. More like a 0.37A offset. I mention that because I’m familiar with using the Kore carriers and yet to get hold of an Airbot Systems carrier, but I think one might be showing up soon.
I just checked the parameter description and it reads like your theory, so I’m going to check the code now and see what it does.
I’m still suspecting the PDB is positioned wrong in the wiring layout.
EDIT:
The code says it’s the analog current signal minus the offset then multiplied
// read current
_state.current_amps = (_curr_pin_analog_source->voltage_average() - _curr_amp_offset) * _curr_amp_per_volt;
So it’s something like (1.2v - 0.35) x 35.79 = 30.42A
assuming the current sensor signal was 1.2v as an example
instead of this with no offset: 1.2v x 35.79 = 42.95A
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This is the connection of the PDB with the sensor, and the motor is indeed connected positive and negative to the connectors on the sides.
So your battery is connected exactly as indicated in this diagram?
And only the battery should be connected there.
Any other speed controllers, BEC’s for servos, accessories, should all be connected to the smaller ± pads along the sides.
I think that is what you are saying. That would be correct and doesn’t explain the -12 amps before arming.
Maybe a photo would be best.
Unless the sensor is faulty I cant see how it would produce a negative current with a typical setup.
There are ESCs that give back power to the battery during braking, but that’s momentary, not continual.
I assume that terminal block at the right side would connect to the ± output tabs.
Maybe a photo of you test setup would help clarify things.
Thanks for the explanation. It was just coincidence then that the two values equalled ~12.4. That math as you have it would be a good addition to the wiki.