Adafruit
Adafruit 12-Key Capacitive Touch Sensor Breakout - MPR121
The Adafruit MPR121 Capacitive Touch Sensor Breakout provides 12 channels of capacitive touch sensing over I2C. The MPR121 handles all the capacitive filteri...
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The Adafruit MPR121 Capacitive Touch Sensor Breakout provides 12 channels of capacitive touch sensing over I2C. The MPR121 handles all the capacitive filtering internally and can be configured for varying sensitivity levels, making it far easier to use than raw analog capacitive sensing.
With four selectable I2C addresses via the ADDR pin, you can connect up to four breakouts on a single bus for a total of 48 touch pads. The board includes a 3V regulator and I2C level shifting for safe use with both 3.3V and 5V microcontrollers, plus an IRQ LED that blinks when touches are detected for easy visual debugging.
Key Features
- 12 Touch Channels – Independent capacitive touch inputs with built-in filtering
- I2C Interface – 4 selectable addresses for up to 48 pads on one bus
- 3/5V Compatible – Onboard 3V regulator and I2C level shifting
- IRQ LED – Visual indicator blinks on touch detection
- Configurable Sensitivity – Adjustable filtering and threshold settings
- Compact Breakout – Pre-soldered MPR121 chip ready for breadboarding
Also Available
- MPR121 Capacitive Touch Shield for Arduino – Shield format with alligator clip pads
Ideal For
- Interactive touch interfaces and control panels
- Musical instruments and touch-based triggers
- Proximity sensing and gesture detection
- Replacing mechanical buttons with touch pads
Package Contents
- 1× Adafruit MPR121 12-key capacitive touch sensor breakout (assembled)
- 1× 0.1" header strip
Specifications
- Sensor Chip – MPR121
- Touch Channels – 12
- Interface – I2C (4 selectable addresses)
- Logic Level – 3.3V or 5V
Jargon buster
Plain-language definitions for the technical terms used above.
- alligator clip
- An alligator clip is a spring-loaded metal clip used to make temporary electrical connections to wires, terminals or test points. It is useful for quick bench testing, but it is less secure than a screw terminal or locking connector.
- breakout
- A breakout board carries a small or fine-pitched component and brings its connections out to standard, breadboard- and header-friendly pins. Describing a part as a breakout means it can be wired into a project without soldering directly to the component's tiny contacts.
- capacitive sensing
- Capacitive sensing detects changes in electrical capacitance caused by a nearby object or material, such as a finger, water, or moisture in soil. It is used for touch buttons, proximity detection, and liquid or moisture-level sensing, and it matters because it can work without exposed metal contacts, avoiding the corrosion that bare probes suffer in damp conditions.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- IRQ
- IRQ (interrupt request) is a signal line a device uses to alert a microcontroller that something needs attention, so the microcontroller does not have to poll continuously. Wiring an IRQ pin to a free input lets code respond promptly to events such as new data being ready.
- LED
- A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.
- Shield
- An add-on board that plugs into a main controller board to give it extra features such as sensing, motor control or communication. Knowing a product supports shields helps you judge whether it can connect neatly into an existing maker-board setup.
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