Discovered something new with my Phantom FC40

kitari · Feb 14, 2015

I went out for a quick flight today, and after the flight I disconnected the battery, turned off the Tx, and was walking back towards the house when a nice gust of wind hit the props and made them spin really fast. All of a sudden one of my lights lit up and my phantom made a solid beep sound. so I held it upright and it stopped. Now keep in mind that my battery is disconnected and my Tx is off, so how could this happen??? I've never heard of a phantom doing this, and it was very strange. Has anybody else experienced this? I'd do it again to show you guys, but I don't wanna risk messing up my phantom.

Woody · Feb 14, 2015

Sounds like a capacitor discharging.

kitari · Feb 14, 2015

Woody said:
Sounds like a capacitor discharging.

Ouch, that doesn't sound good, I hope it's ok. If something did mess up, maybe it won't be too expensive to fix.

sherpa · Feb 14, 2015

Maybe the wind turned one or more of the motors into a generator?

IflyinWY · Feb 15, 2015

It was The Men In Black screwing up and turning on their monitoring device after your flight.

Nidge · Feb 15, 2015

The motor became a simple Dynamo.
You can test this for yourself if you have a multimeter. Set the meter to AC and measure across any two of the three motor wires. Spin the prop by hand and you should see a reading on the multimeter. Now set the meter to measure DC voltage and place the probes across the two wires that connect the input of the ESC. Spin the prop by hand and again you should see a small voltage displayed on the meter. The ESC is working in reverse and converting the AC output of the motor into DC. If the motor spins fast enough it will produce enough current to momentarily energise the Phantom's electronics.

Regards

Nidge

Monte55 · Feb 15, 2015

I agree. I have an electric scooter. With the power switch off, if I push scooter forward the battery status lights on handlebar will glow a bit. What's odd is that it's easy to push forward but not backward.

kitari · Feb 15, 2015

Nidge said:
The motor became a simple Dynamo.
You can test this for yourself if you have a multimeter. Set the meter to AC and measure across any two of the three motor wires. Spin the prop by hand and you should see a reading on the multimeter. Now set the meter to measure DC voltage and place the probes across the two wires that connect the input of the ESC. Spin the prop by hand and again you should see a small voltage displayed on the meter. The ESC is working in reverse and converting the AC output of the motor into DC. If the motor spins fast enough it will produce enough current to momentarily energise the Phantom's electronics.

Regards

Nidge

Wow, that's pretty cool. I learn something new every day on this forum. I'll have to try that some time. I wonder if you could use those motors and props as a mini wind powered generator like sherpa was talking about? That could be useful right?

kitari · Feb 15, 2015

IflyinWY said:
It was The Men In Black screwing up and turning on their monitoring device after your flight.

:lol: Thanks, now I'm gonna have that song stuck in my head all day!

J.James · Jun 2, 2015

I attest that spinning the motors makes them work like a dynamo and generate electric. One time when a power wire broke off on the circuit board of my fc40 on night last summer. As it was plummeting back to earth I could see the lights come back on faintly as it was falling. When I got it back the next day there was also even one more file created on the flytrex after the one from the flight that ended when the power went out. It took me a bit to figure out that it had to of been from the props spining the motor being there was no way it was going to get power from the battery with one of the main leads off.

Then when we were riding back in the car and I was trying to get some of the mud off the props by holding it out the window of the car as we were driving it back to camp. It caused the start up beeps to happen and powered up with no battery in it.