Brushed Motors: Can They Recover From Turtle Mode?

Turtle mode is a feature in Betaflight that allows users to flip over their upside-down drone without having to manually pick it up. However, this feature only works with brushless motors that support the DShot ESC protocol, which brushed motors do not. While it is possible to run brushed motors in reverse, it is more taxing on the brushes and will shorten their lifespan.

Brushed motors don't support DShot, so Turtle mode won't work

Brushed motors don't support Turtle mode, a feature in Betaflight that allows users to flip over their upside-down drone without having to manually pick it up. This is because Turtle mode only works with the DShot ESC protocol, which brushed motors don't support.

DShot is a protocol that allows the flight controller to send commands to the electronic speed controller (ESC) to control the speed of the drone's motors. The protocol is designed to be fast, reliable, and efficient, making it ideal for use in drones and other unmanned aerial vehicles.

Brushed motors, on the other hand, typically have only one MOSFET controlling each motor, which means they can only spin in one direction. Enabling reversible brushed motors would require more transistors per motor, taking up valuable board space and adding unnecessary complexity.

While brushed motors offer advantages such as better manoeuvrability in tight spaces and quieter operation, they don't support Turtle mode due to their lack of compatibility with the DShot protocol. This is a key consideration for drone enthusiasts, especially those who fly their drones indoors, as it can save them from having to walk over and manually flip their drones after a crash.

While it may be technically possible to enable Turtle mode on brushed motors by adding more transistors and modifying the firmware, it is not a common practice and could potentially void the warranty or cause unforeseen issues. Therefore, for those who want the benefits of Turtle mode, brushless motors are a more suitable option.

Brushed motors are controlled by one MOSFET, so they can only spin in one direction

To enable a brushed motor to spin in both directions, additional transistors would be required. However, this would increase the complexity and cost of the system, and the additional components may not be justified for many applications.

In contrast, brushless DC motors use transistors in the electronic control circuitry to apply and remove power to the rotor's wire, producing an alternating current that enables continuous rotation in either direction. Brushless motors offer higher torque-to-power ratios, higher speeds, and more precise control compared to brushed motors. They also have a longer operational life due to the absence of brushes, which can wear out over time.

While brushed motors are limited to spinning in one direction, they have several advantages over brushless motors. Brushed motors are typically lower in cost and simpler to control. They are also quieter, making them more suitable for use in public spaces or when trying to minimise noise for others in the household. Additionally, brushed motors are generally less abusive on batteries, providing longer flight times.

Brushed motors wear out faster than brushless motors

Brushed motors have been in production for over a century and are known for their simplistic design. They utilize a pair of carbon brushes to deliver power to the motor. The brushes cause friction, meaning some of the energy supplied is used to overcome that friction. Friction also causes a loss of voltage, which reduces the amount of energy driving the tool. This is especially important for battery-powered tools, which have a finite amount of power available per charge.

Brushless motors, on the other hand, do not have physical brushes and commutators. They use a hall effect sensor and a control circuit to ensure the opposing magnetic poles of the stator and rotor always align. This design is more efficient, as it turns more of the electricity produced into usable energy. Brushless motors also don't suffer from the same levels of drag and associated heat build, meaning they can reach their desired speed more quickly, run faster for longer, and usually deliver more torque for equivalent power consumption.

The lack of brushes and commutators in brushless motors also means there are no replaceable parts, so they are maintenance-free. They also tend to have a significantly longer working life. Brushed motors, on the other hand, require more maintenance and can be inconvenient to fix, as power tool manufacturers don't always make it easy to access a given tool's motor. Eventually, commutators can wear out, and the construction of a motor may not make replacement feasible.

Brushed motors are less powerful than brushless motors

The primary difference between brushed and brushless motors is that brushed motors are mechanically driven, while brushless motors are electronically driven. In brushed motors, the stationary part, or stator, contains permanent magnets, while the moving part, or rotor, contains electromagnets. The rotor becomes electromagnetic when powered, and the carbon brushes deliver power to the commutator ring, which then activates the rotor.

Brushless motors, on the other hand, have a more complex design. They use a hall effect sensor and a control circuit to ensure the opposing magnetic poles of the stator and rotor always align. This allows brushless motors to generate more torque than brushed motors.

The design of brushed motors, with their carbon brushes, also causes friction, which results in energy loss. This friction also leads to a loss of voltage, reducing the amount of energy driving the tool or appliance. In contrast, brushless motors do not have brushes, resulting in less friction and more efficient energy use. This increased efficiency means that brushless motors can run longer on the same battery power.

Additionally, the brushes in brushed motors eventually wear out due to the friction, requiring more maintenance and replacement parts. This adds to the overall cost of ownership. Brushless motors, on the other hand, are maintenance-free and tend to have a longer working life.

While brushed motors are less powerful, they do have some advantages. They are typically less expensive than brushless motors and are suitable for use in momentary short bursts or when the appliance is used only occasionally. Brushed motors are also preferred in extreme operating conditions as they do not require sensors or control circuits that may fail in harsh weather.

Brushed motors are quieter than brushless motors

The difference in noise level between brushed and brushless motors is particularly noticeable when flying a drone indoors. The quieter brushless motors are more acceptable in public spaces and less likely to annoy others in the same household.

In addition to being quieter, brushless motors offer several other advantages over brushed motors. They produce less heat, are more energy-efficient, require less maintenance, and have a higher power-to-weight ratio. However, they also tend to be more expensive.

While brushed motors may be cheaper and better suited for some specific use cases, such as indoor drone racing, the overall superiority of brushless motors in terms of noise, efficiency, and maintenance makes them the preferred choice for most applications.

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