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PWM

The PWM signal controls the amount of energy delivered to the device, usually a DC motor, LED light, bulb, etc. To control voltage, instead of using inefficient resistance-based voltage dividers (the remaining part of the voltage is distracted as heat), PWM is based on approximating the energy delivered to the device with periodical switching on and off. Only two voltages are delivered to the device: low (0V) and HIGH (Vcc). One can observe it, e.g. when dimming the LED when recorded with a high fps camera: the LED light flashes with the PWM signal frequency.
PWM controls, in fact, the ratio between HIGH and LOW signals in one period: the higher the ratio, the more energy is being delivered to the device. It is called a duty cycle. A perfect square wave signal, usually referenced as a clock signal, has a duty cycle of 50% (or 0.5); thus, its energy is half of the energy that can be carried when the signal is HIGH all the time.

Some devices are fragile to the changes and cannot accept instant on and off. For this reason, we can use a capacitor that acts as an intermediate accumulator of the energy and thus flattens the characteristics.
en/iot-open/embeddedcommunicationprotocols2/pwm.1692614276.txt.gz · Last modified: 2023/08/21 07:37 (external edit)
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