3×4 Flexible Keypad

Wiring Connections:

• Pin 1: Connect to a digital input pin (row 1).
• Pin 2: Connect to a digital input pin (row 2).
• Pin 3: Connect to a digital input pin (row 3).
• Pin 4: Connect to a digital input pin (row 4).
• Pin 5: Connect to a digital input pin (column 1).
• Pin 6: Connect to a digital input pin (column 2).
• Pin 7: Connect to a digital input pin (column 3).

Power:

• Operating Voltage: The keypad itself does not require a dedicated power supply; it works passively by creating connections between rows and columns when a key is pressed.
• Current Consumption: Negligible, as the keypad does not consume power on its own.

Input and Output:

• Input:
  • Pressing a Key: When a key is pressed, it creates a connection between the corresponding row and column.
  • Microcontroller: The microcontroller detects which row and column are connected, determining the pressed key.
• Output:
  • Key Press Detection: The microcontroller interprets the row and column signals to identify the key that has been pressed.

Physical Characteristics:

• Dimensions: Typically around 70 mm x 50 mm, although sizes can vary slightly between manufacturers.
• Thickness: Extremely thin, usually less than 1 mm, making it flexible.
• Weight: Very light, often less than 5 grams.
• Color: Typically black with white printed numbers and symbols.
• Cable Length: The flat ribbon cable is usually around 70 mm long.

Technical Specifications:

• Key Contact Resistance: Typically less than 200 ohms, depending on the key and the pressure applied.
• Life Span: Each key is rated for over 1 million presses.
• Operating Temperature: Usually between -20°C to +60°C, making it suitable for most indoor environments.
• Connection Type: Simple row-column matrix, allowing for easy detection of key presses through digital I/O pins.

Additional Features:

• Flexible and Durable: The keypad is designed to withstand repeated bending and pressing, making it reliable for long-term use.
• Customizable: Some keypads may allow for custom printing of symbols or numbers, depending on the manufacturer.
• Easy Integration: Compatible with a wide range of microcontrollers, including Arduino, Raspberry Pi, and other development platforms.

How to Use:

• Connection:
  • Attach the Keypad: Use the adhesive backing to mount the keypad onto the desired surface.
  • Connect the Ribbon Cable: Insert the ribbon cable into the appropriate pins on your microcontroller or development board. Ensure the pins match the correct rows and columns as per your wiring.
• Programming:
  • Initialize Pins: In your code, designate the connected pins as input pins. Pull-up resistors may be used to avoid floating pins.
  • Scan for Key Presses: Create a loop that scans the rows and columns to detect when a key is pressed. This is typically done by setting columns as outputs and rows as inputs, then cycling through the columns while reading the row states.
  • Identify Key: Use the row and column that is activated to determine which key has been pressed. A simple lookup table can be used to map row-column combinations to specific keys.
  • Debounce Handling: Implement a debounce routine to avoid detecting multiple presses from a single key press due to noise or quick contact.
• Example Application:
  • Inputting Data: Use the keypad in a project where users need to enter numeric data, such as a passcode or a phone number.
  • Menu Navigation: Utilize the keys to navigate through menus in an embedded system, providing simple user interaction without needing a full keyboard.

The 3×4 Flexible Keypad is an excellent choice for projects requiring a simple and effective user input method. Its flexible design and straightforward operation make it ideal for embedded systems, access control, and any application where numeric input is needed.