Light Sensor Tone control

Duration: 30 - 45 minutes

playing tones with light sensor

The micro:bit LEDs Light Sensors

• the micro:bit can detect external light level intensity reaching the LEDs
• the light level block reports a reading of values 0 (dark) to 255 (bright)
• a Forever Loop is required to continually measure the current light level and control the tone

Forever Loop

The forever loop really does run forever. The forever loop is useful when there is a need to continually check for an event or use a changing value in code.

Blocks

basic.forever(function () {})
input.lightLevel()
led.plotBarGraph(0, 255)
music.playTone(Note.C, music.beat(BeatFraction.Quarter))

Step 1: Create a light level detector

basic.forever(function () {
    led.plotBarGraph(input.lightLevel(), 255)
})

Build the blocks

• From Basic drag a forever loop block into the coding area
• From Led drag a plot bar graph block into the forever loop
• From Input drag a light level block into plot bar graph of

Set the plot bar graph value up to = 255

Step 2: Test the light required to move the bar graph height

graphing light input

Experiment to see the effect on graph height when the plot bar graph value up to is changed

255 is the maximum light input reading, try numbers smaller than 255 Find a value that allows the graph to show 1 - 5 bars

music.playTone(261, music.beat(BeatFraction.Half))

music.playTone(261, music.beat(BeatFraction.Half))

Step 3: Multiply Frequency using Math blocks

input.onButtonPressed(Button.A, function () {
    music.playTone(261 * 2, music.beat(BeatFraction.Half))
})

Create a play tone block using a Math section, multiplication block to set tone

Next

Add a B button block that multiplies the 261 tone by a number other than 2 to set tone

Download the code to the micro:bit

Test the sound for multiples of the 261Hz C frequency

Step 4: Control the Frequency with the light input

basic.forever(function () {
    music.playTone(input.lightLevel() * 25, music.beat(BeatFraction.Quarter))
})

Create a forever loop containing a play tone block

Set tone, using Math multiplication block that multiplies light level input by 25 or experiment with multipliers larger and smaller than 25

Test light tone control on the guitar Cover the LEDs with your hand to vary light detected to control the tone

Good work, this guitar is sounding good!

Challenge: Create a variable for the light level multiplier that you can change using buttons (optional)