116 lines
3.6 KiB
Markdown
116 lines
3.6 KiB
Markdown
# Light Sensor Tone control
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### @description micro:bit guitar: using light sensor to control tone
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### ~avatar avatar
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Use the Light Sensor to the control tone for this [Theremin](https://en.wikipedia.org/wiki/Theremin) inspired guitar
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* **Concepts:**
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* Inputs
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* Light Intensity
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* Tone/Frequency
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* Ratio Mapping
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* Forever Loop
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* Math (multiplication) with code properties
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### ~
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## Duration: 30 - 45 minutes
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*playing tones with light sensor*
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https://youtu.be/2cKg9pokVC4
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## The micro:bit LEDs Light Sensors
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- the micro:bit can detect external light level intensity reaching the LEDs
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- the light level block reports a reading of values 0 (*dark*) to 255 (*bright*)
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- a **Forever Loop** is required to continually measure the current light level and control the tone
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## Forever Loop
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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.
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## Blocks
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```cards
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basic.forever(() => {})
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input.lightLevel()
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led.plotBarGraph(0, 255)
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music.playTone(Note.C, music.beat(BeatFraction.Quarter))
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```
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## Step 1: Create a light level detector
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```blocks
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basic.forever(() => {
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led.plotBarGraph(input.lightLevel(), 255)
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})
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```
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**Build the blocks**
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* From **Basic** drag a **forever loop** block into the coding area
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* From **Led** drag a **plot bar graph** block into the **forever loop**
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* From **Input** drag a **light level** block into **plot bar graph *of***
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**Set the *plot bar graph* value *up to* = *255* **
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## Step 2: Test the light required to move the bar graph height
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*graphing light input*
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https://youtu.be/pqU7bTcfQ_s
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Experiment to see the effect on graph height when the **plot bar graph** value ***up to*** is changed
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**255 is the maximum light input reading**, try numbers smaller than 255
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**Find a value** that allows the graph to show 1 - 5 bars
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### ~hint
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### Frequency
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**Frequency** measured in Hz which are cycles per second or vibrations per second
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* A healthy human ear can detect frequencies in the range of 20Hz to 20,000Hz.
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* The micro:bit + headphones reliably produce detectable output ~50Hz - 6,000Hz.
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**261Hz** represents a C note
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```blocks
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music.playTone(261, music.beat(BeatFraction.Half))
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```
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**play tone** blocks can specify a numeric **Frequency**
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by replacing the letter **C** note with a **number** block that has the value it represents
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```blocks
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music.playTone(261, music.beat(BeatFraction.Half))
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```
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### ~
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## Step 3: Multiply Frequency using Math blocks
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```blocks
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input.onButtonPressed(Button.A, () => {
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music.playTone(261 * 2, music.beat(BeatFraction.Half))
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})
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```
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Create a **play tone** block using a **Math** section, **multiplication** block to set *tone*
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### Next
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**Add** a **B** button block that multiplies the **261** tone by a number other than 2 to set tone
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**Download the code to the micro:bit**
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**Test the sound for multiples of the 261Hz *C* frequency**
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## Step 4: Control the Frequency with the light input
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```blocks
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basic.forever(() => {
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music.playTone(input.lightLevel() * 25, music.beat(BeatFraction.Quarter))
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})
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```
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**Create a *forever loop* containing a *play tone* block**
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**Set *tone*, using *Math* multiplication block that multiplies *light level* input by 25**
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or experiment with multipliers larger and smaller than 25
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**Test light tone control on the guitar**
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Cover the LEDs with your hand to vary light detected to control the tone
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## Good work, this guitar is sounding good!
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**Challenge:** Create a variable for the light level multiplier that you can change using buttons (optional)
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### ~button /projects/guitar/accelerometer
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NEXT: Accelerometer Beat control
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### ~
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