Electronics > Projects, Designs, and Technical Stuff

Hobbyist RC plane brushless DC motor

(1/5) > >>

cyberfish:
Does anyone have experience driving hobbyist RC plane use brushless DC motors?

I have this one: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7520

Seems like it has 12 solenoids, so 4 electrical revolutions per mechanical revolution (but that shouldn't matter, right?).

And I can't seem to drive it properly.

With power supply set to 0.5A limit, I tried giving it this pattern by hand -

UL, VH (U phase low, V phase high, W phase floating)
UL, WH
VL, WH
VL, UH
WL, UH
WL, VH

But it just doesn't want to turn. It would snap to first position, then when I apply subsequent steps, it would move a little, around the current position. Way less than how much they should move, and in seemingly random direction each time.

Anyone wants to take a guess as to what may be going on?

Thanks

scrat:
The sequence seems right for making the motor rotate.

I think it's not so easy to apply the steps manually...
What is your setup? Switches? Wires and hands?
If you use switches, then a free-wheeling diode should be put there, but I think that, however, current has the time to go to zero while switching from one phase to the other, So rotor could place itself in a quite random position at every phase change.

If you really need this, try making a little 3-phase inverter. You can find one already done on CD players or computer fans. Computer fans have a controller that takes simply a DC voltage, and does the switching for you.

Simon:
do you need such accuracy in an RC plane ? surely your adding extra weight as oposed to a brushed motor ?

scrat:
Brushless DC aren't very accurate motors, in fact they are the ones used for low-cost high-reliability applications (e.g. PC fans) because of their lack of brushes (which, besides poor duration, produce sparks and so great noise).

Constructively they are little different from brushless AC motors (they can even be the same) but they are driven in a DC-like way (a DC current for one third of a period each phase).

Simon:
Oh well whats the point then ? your adding extra weight to a plane

Navigation

[0] Message Index

[#] Next page