I have a damaged RC drone/quad. It has an all in one FC/ESC. The "all in one" is brand new.
One of its motors is twitchy/does not spin. That motor is tested to be good. I tested it by swapping a new motor and saw the same result (twitchey ness).
The drone software is able to view the microprocessor that controls the bad motor. It looks fine.
The motor has three wires on it. Each wire is connected to a pad where there are 2 MOSFETs per pad. One will switch the negative, one will switch the positive. There is probably a chip to switch these in sequence and measure back EMF. There appears to be no damage visually. No motor pad is shorted to ground or positive battery terminal.
When the motor is powered, it twitches. Again, it is not a motor problem, it is an ESC problem in the fc/"all in one". I have read elsewhere that if a single wire is bad on the three phases going to the motor, the result will be twitchiness. That is not the case, all the wires have good solder joints.
I also tested that if the motor is disconnected, there is no short between any of the three ESC pads. I tested that none of the three ESC pads has a short to either the positive or negative terminals leading to the battery.
I want to narrow down to which of the three ESC pads is bad in need of further debugging. If it is a bad MOSFET that will not switch on on say pad one, then I can replace it and hope all is well. It is a small "all in one."
I have a hot air station and oscilloscope. I wanted to minimize desoldering any components, especially those feeding ESC pads that are in good shape.
I also have a "smoke stopper". If I power the FC and spin the motor, it will twitch and then the stopper will shut off power (keeping the smoke in.) I do not remember any particular ESCs being warm to the touch after this has happened.
Using my oscilloscope, I am how wondering how I can connect it to the three phases/pads along with the connected motor and see what trace is "not like the others" and then pull MOSFETs and check components along that channel.
I envision that once connected, I can power the ESC, see the motor twitch, and then look at what trace is missing on the scope. I can then check MOSFETs along that channel as well as.
How can I attach my oscilloscope to the twitchy motor to locate what to do next? Where would ground connect? Should I add resistors between the scope probe and motor lead? I do not want to damage the scope with back EMF or high voltages. The drone uses a 12 volt battery.
My hope is to see just enough to narrow to a channel. I suppose if all looks the same then it is the controller along that channel.