This creates a wave which varies between -127 and 127. To get our sine wave to fill this range we first multiply the sine wave by 127 (A). However, on the Arduino the duty cycle of a PWM signal is set by an integer between 0 and 255. A typical sine wave varies between 1 and -1 centered at 0. Next up is A which is known as the amplitude or scaling factor of the wave and C which represents the offset. In the above formula N represents the total number of samples it will take to traverse a full cycle of the sine wave. I used a 47K ohm resistor and a 0.1uF capacitor to accomplish this. This should give me a good balance between stability and low settling time. After the experiments in my last post I settled on an RC value of 0.005 (or 0.0047 more accurately). To get started I set up an RC Low Pass Filter. The Filter Low Pass Filter With RC=0.0047 If you are interested in creating an audio oscillator using your Arduino I would recommend looking into off-board DACs (Digital to Analog Converters) which use serial communication with the board to provide much higher output speeds and resolutions. An LFO or envelope generator though are still realistic goals. However, the idea of creating an full audio oscillator with this method is an impossibility. This means we can push our samples much closer than the normal settling time discussed in my last post. One nice thing about the sine wave is that the changes in voltage through the wave are continuous. I’ve had some success creating “relatively” clean 100Hz waves but going much higher than this results in the wave breaking down entirely. The fewer cycles you have per wave the more misshapen your output wave will be. As an example if I wanted a sin wave with a frequency of 100Hz I would only be able to use approximately 10 PWM cycles per sine wave. The Arduino has a maximum PWM frequency of 980Hz which is quite low, especially when working in the audio space. Know Thy Limitsīefore I go to far into this project I want to talk a little bit about the limitations of the Arduino.

I’m going to focus on creating a workable 10Hz sine wave and then in forthcoming posts I’ll look at manipulating the frequency and modelling more interesting wave-forms. I want to get my Arduino outputting sine waves. Today it’s time to apply those basics to something a little more interesting. I’ve spent the last few weeks going over the fundamentals of PWM and implementing them on my Arduino Uno.

Arduino multisim 11