How to Use Other Potentiometers with MgcSTEM PWM Products

1. Potentiometer Compatibility

The P pin is designed to read a voltage signal. Almost any potentiometer can be used with an MgcSTEM PWM controller module, as long as it provides a valid speed control voltage signal to the P pin.

2. Recommended Potentiometer Resistance and Wiring

We generally recommend using a 5 kΩ or 10 kΩ potentiometer.

Connect the potentiometer as follows:

• Connect one of the two outer terminals to 0V (GND).

• Connect the other outer terminal to +5V.

• Connect the middle terminal (wiper) to the P pin for the speed control signal.

3. Input Voltage Range

The controller accepts an input signal ranging from 0V to 5V, with an effective speed control range of 1V to 4V.

Do not apply a voltage higher than 5V to the signal pin, as this may damage the controller.

4. Speed Signal Detection at Power-Up

This is the most important point to note.

When the PWM controller powers on, it checks the input signal voltage. The controller will only enter potentiometer-based speed control mode if the detected voltage is above 0.3V. Once this condition is met, the potentiometer speed control function is enabled.

Therefore, do not turn the potentiometer all the way down to its minimum position before powering on the controller. Make sure the voltage at the P pin remains above 0.3V during startup.

To avoid this issue, you can add a resistor in series with the potentiometer circuit so that the voltage at the P pin does not drop to 0V, even when the potentiometer is turned to its minimum position.

5. Output Behavior at Different Input Voltages

The motor output responds to the voltage at the P pin as follows:

• P pin voltage ≤ 1V: The motor output is zero.

• P pin voltage ≥ 4V: The PWM output duty cycle reaches 100%, allowing the motor to operate at full power.

• P pin voltage between 1V and 4V: The motor speed changes linearly with the input voltage.

Important Notes

Please follow the specifications and wiring instructions above when using a different potentiometer with an MgcSTEM PWM controller. Incorrect wiring or failure to meet the startup voltage requirement may prevent the speed control function from working properly.