Accelerometer Beat Control

Use the Accelerometer to control guitar tempo

  • Concepts:
    • Gravity
    • Acceleration
    • X, Y, Z coordinates
    • Tempo
    • Beat
    • Mapping
    • Graphing
    • Absolute value

Duration: 30 - 45 minutes

accelerometer controlled tempo

Blocks

input.acceleration(Dimension.Y)
music.setTempo(120)
pins.map(0, 0, 1023,60, 320)
Math.abs(1)

Accelerometer, gravity and tilting!

The micro:bit contains an accelerometer sensor that is able to measure forces applied to the board. On earth, we are subject to the gravity force which pulls us to the ground!

When the micro:bit is flat on a table, with the screen pointing up, the gravity force is aligned with the Z axis of the micro:bit.

micro:bit x, y, z axis image

If you tilt it up and down, the force will align with the Y axis – this is how we can detect tilting!!! If the force along Y grows, the micro:bit is tilting more and more vertically!

Measuring Acceleration along different coordinates (X, Y, Z axis)

The acceleration block approximately measures milli-g, which is 1/1000 of a g or the acceleration of gravity.

Step 1: Graphing acceleration

basic.forever(() => {
    led.plotBarGraph(input.acceleration(Dimension.Y), 1023)
})

Create the code that measures the change in the Y axis acceleration as a graph on the LEDs

Download the code to the micro:bit

Test the movements that move the graph from 1 to 5 bars on the LEDs

Extra

Try graphing the acceleration along the X and Z axis. Can you explain the differences?

Mapping

It is common to map one standard to another - such as with temperature
Fahrenheit to Celsius

Step 2: Mapping acceleration to Beat

micro:bit sensors produce signal values between 0 to 1023. The map block converts the signal to a desired range.

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
         music.playTone(Note.C, music.beat(BeatFraction.Quarter));
})

Create the code that Maps Y axis acceleration as tempo

Download the code to the micro:bit on the guitar

Test the movements that speed and slow the tempo

Step 3: Combine with light sensor tone control

Put it all together!

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
        music.playTone(
            input.lightLevel() * 25,
            music.beat(BeatFraction.Quarter)
        );
})

Combine the code above with the light sensor tone control code from the previous activity

Download the code to the micro:bit on the guitar

Now play the guitar adjusting tone and tempo using the light sensor and accelerometer!

NEXT: Pin Press on/off