LED Strip Light Meter

Code

The code in the editor below is ready to run! Plug your Code Lab in to your computer's USB port with the cable and hit 'Upload Your Code!' to see what it does. Change something in the code, like a delay or pin number. Try to add something new to the program - it's yours to tinker with! You can always press the 'Restore' button to return the code to the working example.


/* Create an LED 'light meter' that lights more pixels when there is less light on the sensor */ #include "LEDStrip.h" //The LEDStrip.h library gives your code access to special functions exclusive to the LED Strip LEDStrip strip = LEDStrip(50, 13, 12); //Set up the strip by defining how many pixels (50) and which pins of the microchip are used (always 13 and 12 on Code Lab) void setup() { pinMode(A2,INPUT); //light sensor } void loop() { int pixelCount = analogRead(A2); //create a variable named pixelCount that is an integer and checks the reading from port A2 pixelCount = map(pixelCount,0,1023,49,0); //'map' the readings from A2 onto the pixels of the LED strip //Now a reading of 0 on the light sensor = 49 on the LED strip. A light reading of 1023 = 0. A reading of 512 = 25 strip.clear(); //clear the strip before you start showing the pixels on it /* Create a variable i that has a starting value of 0 and, as long as i is less than pixelCount, run the code between the curly braces, then increase the value of the 'i' variable by 1*/ for(int i = 0; i < pixelCount; i++){ strip.setPixel(i,200); //Use the variable 'i' to set which LED pixel is being lit up } strip.draw(); //send the setPixel data to the LED strip } // (c) 2021 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense
 

Walkthrough Video

Watch the video for a line-by-line explanation of how the example program works. Then you'll be ready to make some changes of your own!

Video Notes for Code Lab Users:

  • You will use “50” instead of “15” as the first argument in your LEDStrip function.

  • The second and third arguments of the LEDStrip function (13 and 12) do not need to change. These connections are permanently set on Code Lab.

  • Your “map” function has an argument of 49 instead of 14 because you have 50 LEDs on your Code Lab. The video references an LED strip with only 15 LEDs.

  • The video walks through an example using a light value of 500. With Code Lab, this will translate to about 25 LED pixels lit, not 7.

Use this spectrum to estimate the color values you'll need for your 'setPixel' arguments to achieve your favorite color!

This graphic shows how some of the values from the light sensor will 'map' onto the number of LED strip pixels.

Challenges

Can you complete the challenges? Change the code in your code editor above. Upload your code to see the effect when you're finished. Complete a challenge? Check it off the list!

Concepts

These are the new code concepts covered in this example program. To become a great coder, read through these concepts to learn new vocabulary.

Quiz

If you're having trouble, try to run an experimental program or look at the example code to help you find the answer.

1. Which syntax ends the entire 'void loop' function?




2. Which syntax ends a single code command?