Sensored has stopped working.

[RudolfXC]

[QUOTE=pugs;684805]

Originally Posted by RudolfXC

If there is more than one FET for each pole of the motor then if one had gone open circuit, it would tesk OK, and the others would still work and drive the motor, just less efficiently,

Not quite no, it cant switch the open fet at low speed so the motor wont turn unless you spin it to help it on its way, had a few like this, once its up and running the other fets do the work so yeah this is right once its up and running

I was only quoting what would happen if there were say 3 FETs per output and only one was open circuit drain to source. As they are in parallel, the other 2 would still work and drive the motor as normally but would just get warmer. This was the case years ago with brushed ESCs.

[pugs]

I was only quoting what would happen if there were say 3 FETs per output and only one was open circuit drain to source. As they are in parallel, the other 2 would still work and drive the motor as normally but would just get warmer. This was the case years ago with brushed ESCs.[/QUOTE]

Yeah I know what you are saying buddy, but for some reason on brushless it cant turn the motor to start, I am not sure why exactly but I think it reads as a sensor fault when the motor don't turn first time, hence why if you spin it first it works

[imull]

Originally Posted by pugs

Not quite buddy, because with the meter you are reading the ground and output leg of the fet when testing through the motor and battery wires you would need to test from ground, output and the gate leg with a meter to find the open fet properly as it might not show just from ground and output.

Even then it might read the board on the gate leg or switching leg and give a false reading

OK, I stand corrected. I would have thought that you'd need to test the gate out of circuit though, as they too are in parallel and therefore the only way of testing it is in isolation?

[Cardnim]

Well, I dont even pretend to understand the last few posts guys - but you obviously all know what you are talking about and Im very grateful for your expert help and advice.

So, raced with the setup last night, and also did those new test that iMull recommended.

Test results.
- i placed the red probe onto the +ve battery lead (not connected to battery)
- multimeter set to 2000K ohms
- readout was +1
- black probe touched each of the motor wires in turn (motor was connected but not powered): all showed readouts of 0.03

- then switched so the black probe was on the -ve battery lead
- red probe touched each of the 3 motor wires
- +1 constant (didnt change when probe touched or not)

...does this tell us anything else?

One last thing to add:
- the car last night was running without a sensor lead in
- first qualifying went fine
- near end of 2nd qualifying it sporadically lost power, so it was "stuttering"
- by 3rd qualifying and final this stuttering had worsened into the car running at low speeds despite the throttle being full forward.

No real heat from motor or esc
esc software was updated and all settings were good
transmitter batteries new
batteries in car fully charged

Sorry for all this hassle guys, but any idea what might be wrong?

Thanks so much.

[pugs]

OK, I stand corrected. I would have thought that you'd need to test the gate out of circuit though, as they too are in parallel and therefore the only way of testing it is in isolation?[/QUOTE]

Use an analogue meter to trigger them, like you can a transistor, not read with a digital meter, not 100% but it should show up a suspect fet the best way is out of the circuit though yeah

[Cardnim]

So it might not be the FETS after all - is that what we are thinking now?
And Im assuming that means it ISNT fixable?

[pugs]

One last thing to add:
- the car last night was running without a sensor lead in
- first qualifying went fine
- near end of 2nd qualifying it sporadically lost power, so it was "stuttering"
- by 3rd qualifying and final this stuttering had worsened into the car running at low speeds despite the throttle being full forward.

No real heat from motor or esc
esc software was updated and all settings were good
transmitter batteries new
batteries in car fully charged

Sorry for all this hassle guys, but any idea what might be wrong?

Thanks so much. [/QUOTE]

Educated guess, stuttering in sensorless mode, no drive without spinning the motor in sensored mode = fets...... about 90% sure of it buddy, yes its fixable if you have a fet board