Running an outrunner motor without ESC?

Being as an outrunner is AC with three wires and a battery is two wires DC: A) It'll be a challenge to figure which wires to hook where... B) You'll effectively create a direct short frying your battery and motor... C) If you're using lipos, you'll have a handy fire for toasting marshmallows...

PCPhill

On the other hand, people have been doing this with BRUSHED can motors for years in RC gliders with a switch to turn the motor on and off, and in FreeFlight, the battery determines your motor run. This is with NiCad or NiMh cells, LiPos would be a one flight only deal as they'd be discharged too low.

If its a brushless, it won't run at all.

Just sit there and get very hot and smell bad.

I think you're right. Back to the drawing board.

Thanks to both.

Wan

The reason, of course, is such that an electric motor needs a rotating electro-magnetic field to work. In a brushed motor there are the changing contacts via the brushes that switch the coils in use and thus the field, but in a brushless there are none. The rotating magnetic field is produced by the controller, that senses the rpm of the motor and switches current through the _three_ coils at proper pace to make the motor turn.

It would be possible to make circuitry that does the thing. However, a brushless controller is by far the simplest and cheapest way to make the motor run. In free-flight electric models people use controllers to make the motor run, even while they do not have RC. They just use elecronic timers intended to drive servos that actuate triggers to change control surface positions, and consider the speed controller as one additional servo to control.

-Tapio-

| It would be possible to make circuitry that does the thing. However, a | brushless controller is by far the simplest and cheapest way to make the | motor run.

Well, the *simplest* way to make the motor run would be to hook it to a 3 phase AC power supply -- since a brushless motor is identical to a

3 phase AC motor. (You probably want to drop it down from 110v or 220v, however.) You might even be able to make it run on standard 1 phase AC, just like you can often make a 3 phase motor run (inefficiently) on 1 phase AC, but that's not usually a good idea.

As for the circuitry needed to make it run from a DC supply, of course it's possible to make it -- it's in a brushless ESC. But just buying a brushless ESC off the shelf is certainly easier than making your own, though there are instructions for making brushless ESCs out there, and you could just use those, but rip out the part that decodes the servo signal and hardwire full throttle in there.

Though if you don't need speed control, it would be a lot simpler to just use a brushed motor. Run at full speed, good brushless motors aren't much more efficient (when you consider the ESC too) than good brushed motors. Brushed motors just get a bad rap because we spend too much time dealing with ones that aren't good :)

(But brushless motors are generally more efficient when run at partial throttle than similar brushed motors run at partial throttle -- that's important too.)

Thanks, Doug.

Maybe there's hope yet. I will try some of your suggestions.

Wan