Here, we're using a flex sensor as part of a voltage divider circuit. A voltage divider outputs a percentage of the incoming voltage. In this case, one resistor is fixed, the other varies. As the sensor bends, its resistance increases, and the measured voltage decreases. When it is straightened, its resistance decreases, and the measured voltage increases.
This method is used in the Power Glove BLE MIDI project (learn guide coming soon) to read analog values with the Feather Sense board as the fingers are bent.
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