What is the correct way to connect the AttoPilot 180A ground wire without causing a ground loop when using two separately fed 6Ss into a PDB while only sensing one of the packs (I only want to monitor 1 pack)? Pixhawk is powered via the top power port using the original Pixhawk PM via a separate 3S (I’m not running the Pixhawk from the PDB).
I have hit a massive dead end after trawling the forums for hours, help greatly appreciated.
For the reasons and difficulty of having a good reliable power module measuring high currents, voltage, I built AirbotPower board that may interest you,
Looks terrific Hugues, however we need a 10s (50V) solution. Is there any way you can easily modify the board to allow 10s?
The limitation to 8S has to do with the voltage measurement resistor divider which scales the input voltage in the range which is admissible by the Pixhawk ADC, i.e. max 3.3V.
The IC components on board can work with a VCC max of 42V (which should be 10S) but you'd have a saturation of the voltage measurement output between 33V and 42V...
Unfortunately I produce this board in very little volume and can't afford a redesign for 10S. It would be too expensive.
Understood, but can I add a resistor to scale the incoming 10S voltage into the 8S range perhaps?
You could indeed try that but I do not know how easy it would be to solder such small SMDs on the board and to intercept traces.
I was thinking just bring the 8s feed down to 10s into your sensor's pins, and scale it up again with the divider on APM, or, if your sensor would output, say, 4.2v on a 42v reading, place a resistor in between your sensor output and the APM power module port for V to bring it down to 3.3. I'm clearly not an electronics guy, but maybe it can work?
yes that could work. But doing so, you have to be careful not to introduce any inductance or capacitance otherwise it could make the voltage reading fluctuate (like what happens with the attopilot module when adding a resistyor divider on the output). So keep all wires short.
I'd like to know this too -I have 6 Attopilots, 3 90A and 3 180A and they're notoriously inaccurate. I spend hours changing settings, testing, measuring, calibrating, poring over the spec sheets and they still give too low amps at low draw and too high amps on the top end. After a flight, my OSD would show 4400mah used, while the charger reports 5200mah used, and it varies depending on how I fly.
I'm at the point of going back to the traditional cheapy 3dr-like current sensors.
I must be doing something wrong!?
Your post makes me think perhaps I have a ground loop and the actual voltage reading from the I and V pins are corrupted.
I think your issue may have to do with configuration of the sensor via mission planner. Check out http://ardupilot.org/copter/docs/common-using-a-current-sensor.html (scroll down and click "next video".
In addition check all your connections (solder) on the Attopilot and make sure no solder is spilling from one circuit on the G V I pins.
You may want to read my post above for a possible option?
Thanks Tony, that's how I always connect the attopilot up, except the mission planner configuration simply does not work - I have to modify the parameters direcly, especially when installing on an APM 2.6+. Same story with pixhawk.
I simply can't get it to accurately read!