In this lesson, we will use a potentiometer module to turn on/off a LED module . Both modules are connected to Osoyoo Magic I/O board for Arduino.
A potentiometer is a simple knob that provides a variable resistance, which we can read into the Arduino board as an analog value.I n this example, that value controls the light brightness of LED module.
So what’s the difference between an analog value and a digital one? Simply put, digital means on/off, high/low voltage with just two states, i.e. either 0 or 1. But the data state of analog signals is a continuous range, for example, from 1 to 1023; Analog signals include those of light intensity, humidity, temperature, and so on.
In this lesson, a potentiometer, or pot, is used to change the PWM current in the circuit so the brightness of the LED will change accordingly. And since the pot is an analog device, the current change is smooth, thus the blink brightness will gradually get bigger or smaller instead of going through an obvious stepwise process.
What we mean by PWM here is the digitalization of analog signals, which is a process of approaching analog signals. Since the potentiometer inputs analog signals, it should be connected to analog ports, i.e. A0-A5, instead of digital ports.
Connect the Arduino board to your computer using the USB cable. The green power LED (labelled PWR) should go on.
In this example, let’s see how to use potentiometer to change the luminance of an LED and receive the data of the potentiometer in Serial Monitor to see its value change.
Declare two integer variables: Inputvalue, Output Value.
The potentiometer’s value is sent by the analog pin A0 to variable InputValue.
Set the following blocks to print ”Input:” and the InputValue, then jump to the next line automatically.
Click Variables category again, drag an OutputValue block to blank area as following picture:
Click Math category, find the Map block in Math category:
Convert the value from 0-1023 proportionally to that in the range 0-255, and assign it to OutputValue.
Set the following blocks to print”Output”and the OutputValue similarly.
Drag another AnalogWrite block from In/Out section, Set pin 9 as output, and add a Delay for 1 second.
Click Save after programming is done. Select the board type and serial port before uploading. For instause a Uno board, just select Arduino/Genuino Uno.
Next,upload the code. If the uploading fails, check and correct the code according to the prompts.Finally, the status will change to ‘Upload success!’.
As you see, the potentiometer is connected to pin A0 of the Osoyoo Uno board, which can measure voltages from 0V to 5V. The corresponding returned value is from 0 to 1024. The measurement accuracy for voltage change is relatively high.
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