Using variables and while loops to create a cascade effect on your LEDs!

# Duration: 1 hour

## Blocks

while (true) {
}
loops.pause(0)
lights.setLevel(AnalogPin.A0, 0)

## Step 1: Creating your variables

We are going to control the brightness of each LED on the board in a special way. In this step, we create 5 different variables to control each LED. We’ll be controlling each separately from each other!

Variables act as places to keep values that are changed and used many times. Let’s make some variables now.

1. From VARIABLES, click Make a Variable and name it brightness_0.
2. Do this 5 more times, using these names for the variables: brightness_1,brightness_2, brightness_3, brightness_4, and brightness_5.

## Step 2: Setting up your variables

The next thing we need to do is make a starting value for our variables. This allows our program to begin using our variables. Variables are nice because we don’t have to type in an actual value, like 92 or 0, every time we need our program to use a value. The variable holds the value for us. Handy!

1. From CONTROL, drag an ||loops:on start|| block into your workspace.
2. From VARIABLES, drag a ||set|| block into your ||loops:on start|| block.
let item = 0

### Build the block…

From the dropdown in ||set||, select brightness_0 to replace item.

Setting brightness_0 to 0 tells any code that uses the variable that the starting value is 0. Let’s repeat this step for the other 5 variables you created earlier!

let brightness_0 = 0
let brightness_1 = 0
let brightness_2 = 0
let brightness_3 = 0
let brightness_4 = 0
let brightness_5 = 0

## Step 3: Controlling LED 0

Now that the variables are properly defined, let’s start coding the LED lights! we’ll begin with the LED on the very left side.

1. From CONTROL, drag a ||loops:forever|| loop into your workspace.
2. From CONTROL, drag a ||loops:while|| loop and nest it inside your forever loop.
loops.forever(function () {
while (true) {
}
})

### Build the block…

1. From MATH, drag a ||math:(0 == 0)|| into the place of the true of the while loop.
2. From VARIABLES, drag a brightness_0 variable into the left side of the equation.
3. Change the sign from = to <=.
4. Type in 255 for the righthand side.

Now that the while loop is set up, let’s next make the loop do some work.

From LIGHTS, drag a ||lights:set to|| block into the while loop.

let brightness_0 = 0
loops.forever(function () {
while (brightness_0 <= 255) {
lights.setLevel(AnalogPin.A0, 255)
}
})
brightness_0 = 0

### Build the block…

1. From PINS under Advanced, drag a ||pins:D0|| block to replace the ||pins:A0|| inside your blue block. The ||pins:D0|| pin will control LED 0.
2. From VARIABLES drag a brightness_0 into the right side of your ||lights:set D0|| block.
3. From CONTROL, drag a ||loops:pause|| block and place it under your ||lights:set D0|| block inside your ||loops:while|| loop. Change the value to 15 milliseconds.
4. From VARIABLES, drag a ||set|| block and place it under your ||loops:pause|| block.
let brightness_0 = 0
let item = 0
loops.forever(function() {
while (brightness_0 <= 255) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
item = 0
}
})
brightness_0 = 0

### Build the block…

1. Select brightness_0 from the dropdown of variables to change item name in your variable.
2. From MATH, drag out a ||math:0 + 0|| block and place it inside the ||set|| block.
3. From VARIABLES, drag a brightness_0 into the left side of your addition block.
4. Change the value of 0 on the right side to 10.
let brightness_0 = 0
loops.forever(function() {
while (brightness_0 <= 255) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 + 10
}
})
brightness_0 = 0

Let’s run the code now. What do you see? Does your first LED light up and fade in? To make it disappear, we’ll need another ||loops:while|| loop that does almost the same thing, but have it run it with a different condition. Let’s make an identical block to the one which does the fade in, but this time we’ll need to change some values to have it fade out instead of fading in.

When you create your second ||loops:while|| loop, make sure it’s still in your ||loops:forever|| loop under your previous ||loops:while|| loop.

Using nearly the same steps as above, we’ll code the next block. There are some differences in the some of steps here compared to the steps above. Let’s see what gets modified as we build the new block.

### Build the block…

1. Create another ||loops:while|| loop like you just did before.
2. Change the operation in the conditon from = to >=.
3. Change the sign of for the addition of brightness_0 to a subtraction, so that it reads brightness_0 - 10.
let brightness_0 = 0
while (brightness_0 >= 0) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 - 10
}
brightness_0 = 0

Run your code now. Does your LED fade in and out? Here’s what the complete control block should look like!

let brightness_0 = 0
loops.forever(function () {
while (brightness_0 <= 255) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 + 10
}
while (brightness_0 >= 0) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 - 10
}
})
brightness_0 = 0

We’ll repeat the blocks we made to control LED 0 for every variable and every LED, so that we can have each light up. We’ll make changes to each and insert some pause blocks to sequence the flashing of each LED so that they all work in succession.

Before moving on to code the next LEDs, let’s add one more thing to our current code.

Inside the forever loop and under your ||loops:while|| loops, add a ||loops:pause|| block and type in 1500 for the value instead of 100.

let brightness_0 = 0
loops.forever(function () {
while (brightness_0 <= 255) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 + 10
}
while (brightness_0 >= 0) {
lights.setLevel(DigitalPin.D0, brightness_0)
loops.pause(15)
brightness_0 = brightness_0 -10
}
loops.pause(1500)
})
brightness_0 = 0

This seems like a long time to wait. But, to make sure the LED stays off and turns on only after every other LED has lit up, we need to have the loop pause temporarily until 1500 milliseconds (1.5 seconds) have gone by.