AB-026 has been updated to include one further method for stabilising DC motor speed, without the use of external sensors.
This final method uses a ‘Sample and Hold’ circuit to store the value of the motor’s back EMF – which is proportional to the motor speed. Comparing this value with the desired speed (set with potentiometers) we are able to adjust the PWM duty cycle to form a control loop.
Although this method is not suitable for motors with high inductance and has a narrow range of speed regulation, it is more efficient (in terms of power losses) and the measurement is not affected by the ambient temperature.
So to see the updated method, clicking the link below will take you straight to the new section!