I am working on a project with a 3-Wheel Car: 1 Custer Wheel, and 2 DC Motors. I need to steer the car playing with the speeds of these two dc motors. If I would supply a constant voltage and current to the DC motors, is there an equation or maybe a source to know the exact degree of turning by assigning PWM to a certain value? Let's say I want to turn the car 30 Degrees to the left from the straight direction. Can I do calculations to find all of the PWM values or it can only be got through experiments? Thanks in Advance!

  • 2
    you cannot turn a motor a known amount without some kind of feedback
    – jsotola
    Dec 30, 2019 at 9:57
  • As my experience in RC robots as yours, you Can't, simply because the speed of the car rotating varies from a surface to another, on ceramic flat surface the robot will turn so fast,but on a carpet for example the robot will rotate slowly even the signals and the voltages were Similar. Jan 19, 2020 at 12:14
  • As @jsotola said, you would need a feedback, that means a sensor which tells you the angle of your car in order to reach the angle you want, for example use a magnetometer like the HMC5883L Jan 19, 2020 at 12:21

1 Answer 1


Basically you can't. PWM value required to turn to a specific degree will depend on motors, on voltage, on hardware, in the current velocity of the car and probably on the surface under the wheel. Also keep in mind that real cars don't turn like that (at a fixed angle). Instead, driver constantly adjusts the position of the steering wheel, while looking at the road (i.e.a feedback system). Same is for RC cars, operator smoothly deflects the joystick looking at the vehicle.

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