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

glowing pendulum block activity

Construct a pendulum that glows using acceleration.

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

Turn on all the LEDs.

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)

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

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)
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.

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)
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.

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)
basic.forever(() => {
    let 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.

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)
basic.forever(() => {
    let acceleration = input.acceleration(Dimension.Y);
    acceleration = Math.abs(acceleration);
    acceleration = acceleration / 4;
});

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

basic.showLeds(`
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    # # # # #
    `)
basic.forever(() => {
    let acceleration = input.acceleration(Dimension.Y);
    acceleration = Math.abs(acceleration);
    acceleration = acceleration / 4;
    led.setBrightness(acceleration)
});

~avatar avatar

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

~