Arduino Intermediate Kit Tutorial 9: Light Regulator

The light regulator is a device with which you can control brightness of the light. In this session, we’ll show you how to control brightness of the light with an analog rotation sensor. The light will turn from dark to bright or the other way along with the change of the rotation angle. The bigger the rotation angle is, the brighter the LED light is, and vice versa. You can make a light regulator for your own light at home.

The rotation sensor can also be used to control the rotation angle of a steering gear. you can also use it to control the rotational speed of a DC motor. You can find many uses for the rotation sensor.

COMPONENTS

1× Digital Piranha LED-R
1× Analog Rotation Sensor
1× DFRduion UNO R3 (similar as Arduino UNO)
1× IO Expansion Shield for Arduino V7.1

HARDWARE CONNECTION
Attach the potentiometer to analog pin 0
Attach the Digital piranha LED-R to analog pin 10

See the diagram below for reference:

Be sure that your power, ground and signal connections are correct or you risk damaging your components.

When you have connected the components and checked your connections, plug the Arduino in to your PC with the USB cable so you can upload a program.

CODE INPUT

Sample Code 6-1:

// Item Six—Light –regulator
int potPin = 0;                   // Analog Rotation Sensor shall be attached to analog pin NO.0
int ledPin = 10;                  // LED shall be attached to digital pin No.10

void setup() {
       pinMode(ledPin, OUTPUT);
}

void loop() {
  int sensorValue = analogRead(potPin);    // collect value at analog pin No.0       
  // A value between 0 and 1023 to mapped to a value between 0 and 255
int outputValue = map(sensorValue, 0, 1023, 0, 255);   
analogWrite(ledPin, outputValue);   //write corresponding value for LED
  delay(2);                     
}  

CODE REVIEW
We have used the “map” function. The map function is used to map a value within a range to one within another range. Let’s examine it a little closer:

The function’s syntax is as follows:
map(value, fromLow, fromHigh, toLow, toHigh)

The function maps a value between "fromLow” and “fromHigh” to one between “toLow” and “toHigh”.

Meanings of parameters included in the map function:

value： value needs to be mapped

fromLow： lower limit of the current range

fromHigh： upper limit of the current range

toLow： lower limit of the target range

toHigh： upper limit of the target range

One advantage of map function is that the lower limit of both ranges can be a number bigger than their upper limits:
y = map(x, 1, 50, 50, 1); 

The value included in the map function can also be a negative number:
y = map(x, 1, 50, 50, -100);
    
Let’s reexamine the code:
    int outputValue = map(sensorValue, 0, 1023, 0, 255);
The above code is used to map a value (0~1023) read from the analog pin to one used in the PMW pin (0~255).

If you have any questions, please feel free to comment.
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