pxt-microbit/docs/reference/input/acceleration.md

Acceleration

Get the acceleration value (milli g-force) in one of three dimensions, or the combined force in all directions (x, y, and z).

Find the acceleration of the @boardname@ (how fast it is speeding up or slowing down).

input.acceleration(Dimension.X);

~hint

You measure acceleration with the milli-g, which is 1/1000 of a g. A g is as much acceleration as you get from Earth's gravity.

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Parameters

• dimension: the direction you are checking for acceleration, or the total strength of force.

x: acceleration in the left and right direction.
y: acceleration in the forward and backward direction.
z: acceleration in the up and down direction.
strength: the resulting strength of acceleration from all three dimensions (directions).

~hint

Forces in space

Since we don't live on a flat world, forces happen in three dimensional space. If the movement of an object isn't exactly in the direction of one axis, we need a way to calculate its acceleration from the values measured for all the axes together.

If you put your @boardname@ on a level table and push it diagonally, you have an acceleration in two dimensions. You can find the acceleration in that direction just like how you calculate the long side of a triangle using the two shorter sides (X and Y):

strength2D = Math.sqrt((accelX * accelX) + (accelY * accelY))

If you decide to lift your @boardname@ off the table, then you've just added another dimension, so insert the acceleration value for the Z axis into the equation:

strength3D = Math.sqrt((accelX * accelX) + (accelY * accelY) + (accelZ * accelZ))

This calculation is called the Euclidean norm of acceleration.

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Returns

• a number that means the amount of acceleration. When the @boardname@ is lying flat on a surface with the screen pointing up, x is 0, y is 0, z is -1023, and strength is 1023.

Example: bar chart

This example shows the acceleration of the @boardname@ with a bar graph.

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

Example: quake meter

Every 5 seconds, with the @boardname@ facing upward on a flat surface, show how much the earth is shaking (if at all).

basic.forever(() => {
    basic.showNumber(input.acceleration(Dimension.Strength))
    basic.pause(5000)
})

See also

set accelerometer range, compass heading, light level