Steren ARD-020 Manual De Instrucciones página 56

When the pulse is active is half of the period of the signal or duty cycle parameter
is 50%, the effective voltage is half of the total input voltage.
When the duty cycle is reduced to 25%, the effective voltage is a quarter of the
total input voltage. Then the motor speed decreases.
Thus, by controlling the duty cycle or while the pulse is active (frequency), we
can control the DC motor speed.
A way to perform this check on Arduino, is using the PWM analog output.
You should remembered that the PWM output signal (pins 9, 10) is a constant
frequency signal (30769 Hz) and that only allows us to change the "duty cycle"
or the time that the pulse is active (on) or inactive (off), using the analogWrite()
function.
24 24