Why brushless motors have 3 wires

Stepper motors require a sequence of pulses across each wire in order to move. Both motors are part of a RC car and those are DC. The motor should work fine without it. Do not connect the case ground black wire directly to your power ground or signal ground on your controller.

The method or noise reduction shown at the Pololu link Dannyv provided is more common for our robotics applications. Wherever you got your motors from, they may have been intended for an application where the motor case would be grounded to the frame of whatever they were installed in.

Brushless motors will last longer, spin faster, and help batteries last longer. They have three wires instead of two. There are two types: inrunner and outrunner. Brushless inrunners are very similar from the outside to a brushed DC motor in terms of size.

They are usually mounted on a circuit board like a servo motor with a gear box. They spin very fast and have to be geared down like a brushed dc motor. They are different than a brushed dc motor in that they are stronger, more efficient and last longer. They can be matched to a wider variety of propellers or loads by adjusting the gearing.

The five wires coming off the circuit board are the same as those coming off the ESC attached to the brushed dc motor and the servo motor circuit board 2 for power in and 3 go to the arduino. The pulses mean the same as the brushless dc motor. The only difference is that at maximum RPM, there are still pulses. There is not one long pulse like the brushed dc motor. The only physical difference is that there are three wires into the motor you may not be able to see them when it is mounted on a circuit board.

The outrunner is already the standard motor in laser printers, copy machines, fax machines, scanners, blue ray players, cd players, where a very precise, constant speed is needed.

It is also found in model helicopters, RC airplanes and other variable speed applications where there are light weight requirements.

It is totally different than all other motors. It appears to be falling apart like a vacuum cleaner motor. You don't need to tear these apart. Look at these wikicommons pictures. After the retaining ring is removed, the entire assembly that spins can be removed. There may be some resistance that feels like removing magnets from each other.

Underneath the cup of all outrunner brushless motors is a series of coils. On some motors, between the coils, are hall effect probes. Hall effect probes detect the spinning magnetic field and provide a pulse out of the brushless motors to the electronics. From this pulse the electronics can precisely control the speed of the motor. Variable speed motors don't necessary have the hall effect probes. The electronics in the ESC pulses the motor to tell it's initial direction and some other feed back system humans using RC or an autopilot reading accelerometers or gyros adjusts the speed.

Parts of the motor are often attached to a circuit board. Magnets are attached on the inside of the can that spins with the shaft.. All brushless motors have a spinning umbrella. Inside the umbrella is a permanent magnet. It looks like one continuous round magnet. However it is more like series of magnets.

Brushless outrunners are always built on a circuit board. This makes them cheaper. The circuit board for this CD motor has no electronics on it. A ribbon cable attaches 11 wires to another controller circuit board. But often the controller is built onto the same circuit board. The circuit boards interface with a controller in two ways. Fixed speed motors have a cable that contains power, inputs motor on, motor half speed and an output pulse related to the motors motion.

Variable speed motors typically have no circuitry directly associated with the motor. Instead there are typically three wires coming out that attach to an "Electronic Speed Controller. Usually the winding resistance is very low indeed a few hundredths of an ohm. MarkT: RC brushless motors are for driving propellers rather than wheels as there is no way to reverse under load with such sensorless BLDC motors. On RC planes, the Outrunner-model is preferred.

So saying that BLDC is not good for driving wheels, is not correct. It depends on the chemistry of the battery cells and their capacity. There is no answer for such a vague question.