When building a quadcopter, you should test motor spin direction after connecting it to an ESC. If motors on your quadcopter rotate in the wrong direction, it will flip over when you try to take off.
What if my motors are spinning the wrong way?
It’s easy to change motor spin direction, so don’t worry about it when you are building your quadcopter. Just solder the wires up and finish the build, then check motor direction when you are done.
You can either reverse motor spin direction in the ESC settings, or simply swap two of the three motor wires. Check out this guide for more detail.
Using the Motor Tab in Betaflight
The easiest way is to test your motors using the motor tab in Betaflight. Many other flight software offer similar “motor testing” feature including KISS, FlightOne, Cleanflight and Butterflight. This is also available in ESC configurator – BLHeliSuite too.
Enable the checkbox “I understand…”, and increase the slider to spin up the motors.
You can test the motors one by one by putting a propeller on without screwing down the prop nut.
Touch the motor bell lightly with a finger when it’s spinning, and let your finger drag across the bell. You can tell which way the motor is turning as you should feel more resistance if the bell is spinning the opposite direction.
Arm and Check
If you don’t have access to motor testing function for some reasons, you can just try to arm the quad using your transmitter without props on. (Assuming you have finished building your quad, and you have the “motor stop” feature disabled)
Servo Tester or Radio Receiver
You could connect your ESC to a servo tester, or a radio receiver with PWM output. The motor spins as you increase PWM signal. This used to be a very convenient way to check if ESC and motors are working correctly.
However most ESC’s for racing drones these days don’t have a built-in 5V BEC anymore, so you have to somehow supply 5V to the servo tester or radio receiver. Anyway if you find this the easier solution, here is how to do it.
Connect the your ESC to the servo tester or RX (throttle channel).
The receiver or servo tester should be powered by the ESC. If it doesn’t have a 5V BEC, you can get 5V from a spare flight controller. Make sure ground is connected between these components.
Plug in the battery to your ESC and and increase throttle, you should now see the motor begin to spin.