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

glowing pendulum activity

construct a pendulum that glows using acceleration. #docs

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Welcome! This guided activity will teach how to construct a pendulum that glows using acceleration. Let's get started!

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To create a new script, go to the Create Code page and tap New Project under Touch Develop.

Create a forever loop that will constantly display the appropriate brightness on the LED display.

basic.forever(() => {
})

Now let's measure the acceleration on the y axis and store that value in a variable. The input->acceleration("y") function will provide the value.

basic.forever(() => {
    let acceleration = input.acceleration("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.

basic.forever(() => {
    let acceleration1 = input.acceleration("y")
    acceleration1 = math.abs(acceleration1)
})

The function input->acceleration("y") returns a number between 0 and 1024. We want to use this value for the brightness of the micro:bit, but the led->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.

basic.forever(() => {
    let acceleration2 = input.acceleration("y")
    acceleration2 = math.abs(acceleration2)
    acceleration2 = acceleration2 / 4
})

Now let's use our acceleration value to set the brightness on the BBC micro:bit.

basic.forever(() => {
    let acceleration3 = input.acceleration("y")
    acceleration3 = math.abs(acceleration3)
    acceleration3 = acceleration3 / 4
    led.setBrightness(acceleration3)
})

Let's show what the brightness of the micro:bit is by turning all the LEDs on!

basic.forever(() => {
    let acceleration4 = input.acceleration("y")
    acceleration4 = math.abs(acceleration4)
    acceleration4 = acceleration4 / 4
    led.setBrightness(acceleration4)
    led.plotAll()
})

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Excellent, you're ready to continue with the challenges!

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