In the STEM ROV : Propeller making, second post of the STM ROV production sharing series, it mentions that STEM thrusters generally use carbon brush motors due to cost and complexity considerations.
The speed of the carbon brush motor depends on its working voltage. Therefore, the specifications of carbon brush motors usually indicate the number of thousand revolutions per minute at a few volts. Although there is no KV formula for brushless motors, the speed basically increases as the working voltage increases. The running direction of the carbon brush motor is related to the polarity of the working voltage, so the electrode on the back of the carbon brush motor will be marked with the positive position, as shown in the figure below. To change the speed of the carbon brush motor, the operating voltage must be changed. To change the direction of the carbon brush motor, it is necessary to change the polarity of the operating voltage. For brushless motors, the speed and steering are adjusted by the Electronic Speed Controller ESC under a certain working voltage.
STEM ROV controllers are actually rare, and makers usually develop their own circuit boards. For the promotion of STEM ROV, the ROV MAKER team launched the STEM ROV controller that is easy to assemble!!
This controller uses a PWM board to control the carbon brush motor. The scientific name of PWM is Pluse Width Modulation, which is the baseband modulation method in digital communication. Later, it was widely used to control the brightness of the backlight of the mobile phone screen. By adjusting the change in the width of the positive voltage in the PWM cycle signal, the average output voltage is controlled to change the speed of the carbon brush motor. The PWM board designed by ROV MAKER support joystick or knob to control the rotataion speed and direction of the carbon brush motor.
In the design of the controller, the PWM board controls horizontal thruster by joystick. This is because the rocking of the joystick makes the ROV more maneuverable in the horizontal direction, regardless of whether it moves forward/backward or turn around in place. The PWM board controls the vertical thruster by a knob. This is because surface/dive is relatively less frequent, and it is more desirable to maintain the depth within a range at ordinary times.
Following is the STEM ROV controller product links for your referernce :
The ROV MAKER team provides the following videos to share how to assemble the STEM ROV controller t for teaching reference in schools !!