Questions about motors in general

Hello, I’m doing a senior design project where we make an electric skateboard. I was thinking of using one of the motors from the selection here but I’m not super familiar with using motors in general. Would the 24V 37D Metal Gearmotors be enough to drive a skateboard with someone standing on it? I was also thinking the 12V might be enough depending on how much current the rest of the project needs. I also wanted to ask if these would be able to freely spin without damage to the motor when unpowered? I would assume that’d be the case but I just want to be sure. With the motor drivers on the website as well, I’m a little confused about the power and braking with them, if it is only powered by a battery ie only Vin is high and nothing else, would the motor driver put the motor into braking mode or allow it to freely spin?


Unfortunately, none of our motors would be appropriate directly handling a load that high.

Brushed DC gearmotors do not “freely spin” when power is disconnected; the torque required to manually rotate the output shaft will primarily depend on the motor’s cogging torque multiplied by the gear ratio. Turning an unpowered motor generally should not be a problem for the motor as long as you do not exceed recommended load limits (discussed in the product page documentation or datasheet), though that might not be possible for gearmotors with high gear ratios. Also, keep in mind that the generated voltage or current could be problematic for your electronics.

When a motor driver is in brake mode, it is shorting both of the motor outputs (high or low depending on the driver). A common reason for using this (instead of coast mode) is that brake mode makes the relationship between PWM duty cycle and motor speed more linear, but it will also make the motor difficult to turn when it is stopped. How much of a difference it makes will depend on the specific motor, but an easy quick test you can do to get a general idea for your motor is to connect the motor terminals to each other.

- Patrick