pxt-calliope/docs/lessons/glowing-pendulum/activity.md

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2016-03-26 00:47:20 +01:00
# glowing pendulum block activity
Construct a pendulum that glows using acceleration.
To create a new script, go to the [Create Code](/microbit/create-code) page and tap `New Project` under `Block Editor`.
Welcome! This activity will teach how to construct a pendulum that glows using acceleration. Let's get started!
Create a **forever** loop that will constantly display the appropriate brightness on the LED display.
```blocks
basic.forever(() => {
})
```
Now let's measure the acceleration on the `y` axis and store that value in a variable. The `acceleration(y)` function will provide the value.
![](/static/mb/blocks/lessons/glowing-pendulum-1.png)
```blocks
basic.forever(() => {
let acceleration = input.acceleration(Dimension.Y);
});
```
Since the micro:bit will be swinging back and forth, the acceleration will only be positive half of the time. Thus, to always get a positive value, we want to take the absolute value of the acceleration.
![](/static/mb/blocks/lessons/glowing-pendulum-2.png)
```blocks
let acceleration = 0;
basic.forever(() => {
acceleration = input.acceleration(Dimension.Y);
acceleration = Math.abs(acceleration)
});
```
The function `acceleration(y)` returns a number between 0 and 1024. We want to use this value for the brightness of the micro:bit, but the `set brightness()` only accepts a value between 0 and 256. Thus, we need to divide the acceleration by 4 to ensure we will be in the appropriate range.
![](/static/mb/blocks/lessons/glowing-pendulum-3.png)
Now let's use our acceleration value to set the brightness on the micro:bit.
![](/static/mb/blocks/lessons/glowing-pendulum-4.png)
Let's show what the brightness of the micro:bit is by turning all the LEDs on!
![](/static/mb/blocks/lessons/glowing-pendulum-5.png)
### ~avatar avatar
Excellent, you're ready to continue with the [challenges](/microbit/lessons/glowing-pendulum/challenges)!
### ~