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Membrane 4x4 Matrix Keypad
The Membrane 4×4 Matrix Keypad is a compact, ultra-thin 16-button input device designed for microcontroller projects. Featuring keys 0–9, A–D, *, and #, it uses a row-column matrix scanning method that requires only 8 GPIO pins to read all 16 keys — making it ideal for Arduino, ESP32, Raspberry Pi, and similar platforms. The adhesive backing allows quick, tool-free mounting on enclosures, panels, or prototyping surfaces.
Κύρια Χαρακτηριστικά / Key Features
- 4×4 Matrix Layout: 16 keys (0–9, A–D, *, #) in a 4-row × 4-column grid → only 8 GPIO pins needed, saving precious microcontroller I/O resources.
- Operating Voltage 3V–5V DC: Compatible with both 3.3V and 5V logic systems → works directly with Arduino UNO/Mega (5V) and ESP32/Raspberry Pi (3.3V) without level shifting.
- Direct GPIO Interface: No I2C, SPI or special protocol required → rows are driven as outputs, columns read as inputs via simple matrix scanning firmware.
- Ultra-Thin Membrane Construction: Flexible, low-profile design → fits neatly inside enclosures where rigid keypads would not.
- Adhesive Backing: Peel-and-stick mounting → no screws or brackets needed, ideal for permanent installations.
- Key Bounce Time ≤ 5 ms: Low bounce ensures reliable debounce handling in firmware.
- 1,000,000 Closures Life Expectancy: Rated for one million actuations per key → long service life for frequent-use applications.
- Female 2.54 mm Pitch Connector: Standard pitch connector → directly compatible with jumper wires and breadboard setups.
Pinout & Wiring
The keypad exposes an 8-pin ribbon cable with a 2.54 mm female connector. The first 4 pins correspond to Rows (R1–R4) and the last 4 pins to Columns (C1–C4).
| Pin | Symbol | Description |
|---|---|---|
| 1 | R1 | Row 1 — connect to microcontroller output GPIO |
| 2 | R2 | Row 2 — connect to microcontroller output GPIO |
| 3 | R3 | Row 3 — connect to microcontroller output GPIO |
| 4 | R4 | Row 4 — connect to microcontroller output GPIO |
| 5 | C1 | Column 1 — connect to microcontroller input GPIO (with pull-up) |
| 6 | C2 | Column 2 — connect to microcontroller input GPIO (with pull-up) |
| 7 | C3 | Column 3 — connect to microcontroller input GPIO (with pull-up) |
| 8 | C4 | Column 4 — connect to microcontroller input GPIO (with pull-up) |
Wiring note: Connect R1–R4 to 4 digital output pins and C1–C4 to 4 digital input pins (enable internal pull-ups). For Arduino, use the Keypad library for plug-and-play scanning. Example: R1→D9, R2→D8, R3→D7, R4→D6, C1→D5, C2→D4, C3→D3, C4→D2.
Compatibility
- Arduino UNO / Nano / Mega: 5V GPIO — fully compatible, use internal pull-ups via
pinMode(pin, INPUT_PULLUP). - ESP32 / ESP8266: 3.3V GPIO — compatible within the 3V–5V operating range; use 3.3V-tolerant pins.
- Raspberry Pi (any model): 3.3V GPIO — compatible; use RPi.GPIO or gpiozero library for matrix scanning.
- STM32 / Nucleo boards: 3.3V GPIO — compatible with standard matrix keypad libraries.
Τυπικές Εφαρμογές / Typical Applications
- PIN entry and password protection systems for Arduino-based security projects
- Menu navigation and parameter selection in embedded control panels
- Numeric input for LCD-based calculators or data loggers
- Access control systems (door locks, alarm panels)
- Robot control interfaces and tele-operation panels
- Educational projects for learning GPIO matrix scanning and debounce techniques
Τεχνικά Χαρακτηριστικά / Technical Specifications
| Parameter | Value |
|---|---|
| Interface | Direct GPIO (Row-Column Matrix Scanning) |
| Operating Voltage | 3V – 5V DC |
| Maximum Voltage (per key) | 24V DC |
| Maximum Current (per key) | 30 mA |
| Key Layout | 4×4 (16 keys: 0–9, A–D, *, #) |
| Pins Required | 8 GPIO (4 rows + 4 columns) |
| Connector Pitch | Female 2.54 mm |
| Key Bounce Time | ≤ 5 ms |
| Life Expectancy | 1,000,000 closures per key |
| Insulation Resistance | 100 MΩ @ 100V |
| Dielectric Withstand | 250V RMS @ 60Hz, 1 min |
| Operating Temperature | 0°C to 50°C |
| Keypad Dimensions | 69 mm × 79 mm |
| Cable Dimensions | 20 mm × 88 mm |
| Mounting | Adhesive backing (peel-and-stick) |
Συχνές Ερωτήσεις / FAQ
Q: Do I need a special library to use this keypad with Arduino?
A: Yes — the free Keypad library by Mark Stanley & Alexander Brevig (available in the Arduino Library Manager) handles all row/column scanning and debouncing automatically, so you only need to define your pin mapping and key map array.
Q: Can two keys be pressed simultaneously (N-key rollover)?
A: Standard membrane matrix keypads do not support true N-key rollover. Simultaneous key presses may cause phantom key readings. For single-key input applications (PIN entry, menu navigation) this is not an issue.
Package Contents: 1× Membrane 4×4 Matrix Keypad with pre-attached 8-pin ribbon cable (female 2.54 mm connector).