1 Motor 1 Scope - brushless motor, oscilloscope, and a cordless screwdriver

Support my work / pawelspychalski
Our adventure with ESC and brushless motors continues. This time let's connect a BLDC to a cordless screwdriver and an oscilloscope to see how the Back-EMF traces look and how they depend on the rotation speed. Science, mates, science!
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[@baxbanni2226]

I like your hands-on engineering! 👍👍

[@power-max]

All you would need to do is connect 3 1K resistors between the 3 phases and create a virtual ground. The resistors do add a load of 1000 ohms to the 3 phases, however.

[@lasersbee]

You could extrapolate the RPM of the motor by the Frequency of the waves.

[@sjeses]

(1/wave time)*60 = RPM

[@carbidedge]

Super, More videos like this please, Pawel.

[@dutchmetalmaniac]

a new use for my scope. (now i can measure my wind generators 👍) NICE

[@tomascancelliere4348]

Can you share all your important settings for doing this?

[@marhar2]

I would like a video on determining kvm. I have some old motors given to me and would find it very useful to know. (BTW I have the same scope as Pawel. Therefore I am cool!)

[@pablofpv]

Nice scope, I did similar experiments a while back and also used a drill at a known RPM and voltage output of each coil to calculate the Kv of my motors and also some I rewound by hand.Surprisingly accurate enough ,I was basically trying to lower the Kv of motors I had and it did work ,but it was a lot of effort!There are links to video's if you search for radiocontrolinfo/Brushless Motor Kv - Measure a Motor’s Kv 😀

[@MCsCreations]

Pretty interesting, Pawel!!! 😃 There's a video from Great Scott! where he modified a brushless motor to use as a crank generator. Didn't work very well. 😬 Anyway, stay safe there with your family! 🖖😊

[@Siamect]

You don't need a tacho. You see the frequency on the scope.

[@kennethholland1502]

Exactly

[@FPVUniversity]

and some math since electrical RPM is not the sam as physical one. For the simplicity of the video I just ignored that

[@FPV_Thrills]

​@@FPVUniversity what?electrical RPM? is not rpm on oscilloscope .

[@sjeses]

@@FPVUniversity there is a phase shift, but the frequency is related to how many magnets pass the coil in one rotation

[@wavesummit]

Interesting, ive been dealing with a noise on throttle issue, tried LC filters, different capacitors, 12v linear board. Tried two rush vtx, changed the FC from clracing to matek F7. Replaced the hakrc blheli32 with a GS spedix. The issue still persisted. As a last resort I swapped the emax ls 2400kv motor with an old racerstar motor and the noise was gone. After seeing your video I wonder if something went wrong with the motor wires, wonder if I could see something wrong on the oscilloscope by using a drill and turning it like you did.

[@typxxilps]

Could you check all 3 phases at once if you would power the oscilloscope from a battery ? then it should be floating and no ground at all, therefore no short possible - or did I make a mistake ? thx, great idea, will try that out when my loto OSC482 will arrive or tomorrow when I am back in the shed and have the owon vds1022i which has an isolated channel and is battery powered by the tablet connected, but just 2 channel only and the older 8'' android tablet running android 6 for the hscope app.

[@FPV_Thrills]

Why you need thaometer if you have oscilloscop? Just frequency divide by number of magnets

[@yakubyusuf1648]

Can someone tell me the frequency

[@tinochoolun4397]

to pawel nice vdo and explanation also . so i have a question for you what happen if one coil in one phase is missing [burn out] any reply is welcome good job man

[@mattraymond2935]

ESC testing on O scope?

[@IanF-FPV]

I hope Bosch is sponsoring this video🤔🤭

[@LydellAaron]

What model of drill do you have? Online suggests typical cordless drills to output 500 to 2000 RPM. I estimate your motor around 1000-2000KV?

[@FPVUniversity]

The drill is some cheap Bosch. No idea about the model. And motor is 950KV IIRC

[@specialseraphim7]

can we please try this for an esc, so that we could actually see the pwm waveforms?🥺

[@FPVUniversity]

The thing is, that you will not really see waveforms you expect. Scope will show both PWM signal and back-emf. Tried that, huge mess