A call to analogWrite() is on a scale of 0 - 255, such that analogWrite(255) requests a 100% duty cycle (always on), and analogWrite(127) is a 50% duty cycle (on half the time) for example. The Arduino can send PWM signal with the analogWrite() function. The Arduino UNO it has 6 digital pins that can be used as PWM outputs (3, 5, 6, 9, 10, and 11). If you repeat this on-off pattern fast enough with an LED for example, the result is as if the signal is a steady voltage between 0 and 5v controlling the brightness of the LED. To get varying analog values, you change, or modulate, that pulse width. The duration of "on time" is called the pulse width. The analogWrite function has nothing to do with the analog pins. You do not need to call pinMode () to set the pin as an output before calling analogWrite (). Unlike the PWM pins, DAC0 and DAC1 are Digital to Analog converters, and act as true analog outputs. This on-off pattern can simulate voltages in between full on (5 Volts) and off (0 Volts) by changing the portion of the time the signal spends on versus the time that the signal spends off. The Arduino DUE supports analogWrite () on pins 2 through 13, plus pins DAC0 and DAC1. Just imagine a switch to open and close very quickly.ĭigital control is used to create a square wave, a signal switched between on and off. The longer the switch is on compared to the off periods, the higher the total power supplied to the load. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. Pulse Width Modulation, or PWM, is a technique for getting analog results with digital means.
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