I was able to achieve quite a high frequency with this, if I remember correctly almost 100kHz with lower delay-times (I know delays shouldn't be there :)). I stored the values for the sine curve in an array which was created initially. I connected it to the 8 pins of the D port on the arduino (digital pins 0 - 7) so that I could address all the pins simultaneously. It gave a resolution of 1/256*5V, but you could use fewer resistors giving lower resolution. I used the arduino to produce sine waveforms once, using a bunch of 10k and 20k resistors to make an 8 bit resistor ladder. When PWM, DELAY, PWM, DELAY are executed in a loop, the result of this exercise is the brightness of the LED dimming from full brightness to off and repeat.Right now Im accessing an array and using the analogwrite command. In the sketch, we set the PWM from 100% duty cycle to 0% duty cycle in half step with a 200ms delay between each step in a loop. In the example, the value 127 translate to 50% duty cycle. The first parameter is the pin number and the second parameter is the duty cycle from 0 to 255 representing 0% to 100% duty cycle. The analogWrite() function shown above takes two parameters. Once PIN3 is configured as OUTPUT, we can then use analogWrite() as a PWM pin. The above code instructs the STEMTera™ Breadboard to set PIN3 as OUTPUT. The first parameter is the pin number and the second parameter is the mode of the pin. The pinMode() function shown above takes two parameters. In order to turn on the LED, we need to instruct the STEMTera™ Breadboard to set PIN3 to OUTPUT in the setup() function. Understanding the PWM Sketchįrom the circuit, we know that PIN3 of the STEMTera™ Breadboard is connected to the 220Ω resistor and the Red LED. During this stage both yellow LEDs on the STEMTera™ Breadboard will start blinking indicating the Arduino IDE is uploading the sketch to the STEMTera™ Breadboard. After the compilation is completed, the Arduino IDE will start to upload the compiled sketch into the STEMTera™ Breadboard. Once saved, the Arduino IDE will start to compile the sketch. Enter Excercise_2 into the filename field and click save. Void setup () Ĭlick Upload, and the Arduino IDE will prompt you to Save sketch folder as. If you have already done exercise 1, just skip to Write and Upload section. PIN 3, 5, 6, 9, 10 and 11 only.įor this exercise we will be using the same circuit as the one we used for exercise 1. Only PIN with a label ~ can perform as a PWM pin. Not every PIN on the STEMTera™ Breadboard can be used for PWM. 100% duty cycle will have the LED turned ON in full brightness and a 50% duty cycle will have the LED turned ON in half brightness. Furthermore, you should keep in mind that this is a basic. If you don't have one, you can add an external DAC of some sort, which will then generate a true analog output. A 100% duty cycle means the signal is ON all the time.īy varying the duty cycle of a signal, we can control the percentage of ON time for a circuit, hence indirectly control, for example, the brightness of an LED. For that purpose, the Arduino acts as a very basic function generator that can continuously output one of three waveforms: Make sure you use an Arduino with a built-in DAC. The second signal is 30% duty cycle because its ON time is 30% of a cycle and its OFF time is 70% of a cycle. From the above image, the first signal is shown as 10% duty cycle, which means its ON time is 10% of a cycle and its OFF time is 90% of a cycle. In digital electronics, when a signal is at 5V, we call this ON, and when a signal is at 0V, we call this OFF. The duty cycle describes the amount of on-time as a percentage of the total time of a cycle. 1000 Hz frequency would be 1000 cycles per second). The frequency determines how fast the PWM completes a cycle (i.e. Even though this is a modulation technique for encoding information for transmission, it is widely used in controlling the brightness of an LED and the speed of a motor.Ī PWM signal consists of two main components that define its behavior: frequency and duty cycle. Pulse width modulation is a modulation technique used to encode a message into a pulsing signal. | Next Page ❯ Exercise 2 - Pulse Width Modulation (PWM)
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