Brushed motors and brushless motors are two common types of motor used in FPV drones (quadcopters). In this article we are going to discuss the differences between them and why you might want to use one over the other.
The majority of FPV drones use brushless motors because they are way more powerful and durable than brushed motors. However you can still sometimes see brushed motors used in micro and nano drones due to low cost and compactness.
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Construction Differences of Brushed and Brushless Motors
The working principles of brushed and brushless motors are the same, both are based on electromagnetism.
When the motor windings (coils) become energized by current, it creates a temporary magnetic field that repels against or attracts the permanent magnets inside the motor. By alternating the current, you can create a continuous magnetic force that spins the motor around the shaft.
However the construction of the two motor types are very different.
A “brushed” motor has a rotating stator (wire coils) which acts as an electromagnet with two poles. The shell is stationary (not moving) therefore brushed motors can often be mounted without using any screws.
A “brushless” motor uses a permanent magnet and accomplishes the switching by electronically switching the polarity, instead of brushes, hence the name “brushless”. Because of the moving motor bell, the motor is usually mounted by the base using screws.
Advantages of Brushed Motors
- Inexpensive to make
- Can be made in small package
- Favourable in extreme environments due to lack of electronics
- Replaceable brushes for extended life
- Two wire control – control is simple; Brushless motors have 3 wires and require speed controller to work
- No speed controller is required for fixed speed
Popular applications: fan motors, power tools, small motorized toys and computer peripherals.
Advantages of Brushless Motors over Brushed
- No brushes – lower maintenance and longer durability
- More efficient – less energy wasted as heat
- Better speed and torque due to the absence of brushes, because brush friction increases with speed
- Wider speed range
- Better heat dissipation due to the construction compared to brushed motors
- More cost effective for high speed/power operations
Popular applications: radio controlled model airplanes and drones, electric vehicles and industrial machinery that requires high rotation speed and power
Usage of Motors in Drones
Brushless motors are the more popular choice for FPV drones. They are used in almost all types of drones and sizes, including giant heavy lifter to those lower power micro drones that runs on1S LiPo batteries.
With that said, you can still see brushed motors being used in some nano drones that runs on 1S LiPo. Brushless motors are way more flexible as they support much higher voltages, from 1S up to 12S. For example, the popular motors we use on 5″ FPV drones are normally rated for 4S to 6S.
You can check out this table to find out which motor sizes are popular for all sizes of FPV drone here.
Here are the popular brushed motor sizes used in the RC hobby. They are basically size indicators – first two digits are the diameter (e.g. 60=6mm), last two digits are the height (e.g. 15=15mm). Bigger motor = more power.
- 6015
- 7016
- 7020
- 8020
- 8520
3 comments
The sad thing about small brushed motors in RC models is their fragile nature by design. Brushes are tiny springs and copper strips which bend and broke on slight crashes. And even without bashing they wear off fast. From my practice with toy grade and custom made brushed quadcopters with 720 to 8520 brushed motors, small brushed motors got worn beyond repair in a few days of casual flying. Like in after a week or two a month when you run through 6-8 batteries in a day. Even “good” quality motors from western RC shops died in a month. Got very disappointed several times when one of quad brushed motors suddenly died at field without a reason on second-third battery when their “working hours” are exceeded. That convinced me to drop brushed quads completely and move to brushless motors completely. Which works for years while are not bent or smashed into pieces. Response time and power is another argument for brushless motors. And for some time brushless motors already works on 1S batteries with very acceptable flight time. Which eliminated the need for brushed motors completely.
Mike,
Brushed motors use PWM to adjust speed. You’d want to ask for a PWM speed controller.
Bash
Hi Oscar,
Thanks for your brilliant and clear explanations on so many aspects of Drones and flying. I’m a complete novice in the field although I’ve been flying regular RC airplanes in my young days, about 40 years ago.
I recently was cought by the flying fever again and got some parts through banggood, aliexpress and hobbyking and now I’ve built myself a flying F450 drone with NAZA-M and Radiolink. Meanwhile I’m studying the possibility to build something small to fly inside and got some brushed motors and Eangine AIO receiver/controller/esc., and 3D-printed a small fram. One of the big difficulties for me was to find out what to look for when you want to build a brushed-motor quad. In the brushless area it’s clear that there are ESC’s required to generate the CW/CCW pulse, but for brushed motors I’ve not been able to discover what terminology I should look for to make sure my flight controller can control the motors. How is it called when the motors can be connected directly to the FC, what type of device is necessary to connect the PWM output of an FC to a brushed motor, especially for these small Tinywhoop motors. Do you have to take care of ‘protocols’ like DShot, etc, or is that specific for brushless systems.
It would be great if you could give this a thought and maybe add some of the ansers to this tutorial for novices as me.
Thanks
Mike