User’s Guide for the 4 x 3 Rigid Matrix Keypad Module

## 1. Technical Overview

The keypad utilizes a matrix circuit to minimize the number of pins required on your microcontroller. Instead of 12 individual wires (one for each key), it uses a grid of 4 rows and 3 columns, requiring only 7 interface pins.

Specifications

• Key Layout: 0–9, *, # (12 keys total)

• Switch Type: Tactile mechanical buttons

• Operating Voltage: 3.0V to 12V DC

• Pin Pitch: 2.54mm (0.1″) — Breadboard friendly

• Dimensions: Approximately 70mm x 52mm

## 2. Pinout & Wiring Diagram

When looking at the solder pads on the bottom of the module from left to right, the standard configuration is as follows:

Note: Some variations include two extra pins on the far ends for mounting or ground shielding. Only the 7 pins connected to the green PCB traces are required for operation.

## 3. Installation & Connection

A. Hardware Setup

1. Soldering: Solder a 7-pin male header to the green PCB pads.

2. Mounting: Use the four corner mounting holes to secure the keypad to your chassis or project box.

3. Connecting to Microcontroller (e.g., Arduino):

   • Connect Row Pins (1–4) to Digital Pins 9, 8, 7, 6.

   • Connect Column Pins (5–7) to Digital Pins 5, 4, 3.

B. Software Setup

To read the inputs, you must use a “scanning” algorithm. For Arduino users, the Keypad.h library is recommended.

Basic Code Implementation:

#include <Keypad.h>

const byte ROWS = 4; 
const byte COLS = 3; 

char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};

byte rowPins[ROWS] = {9, 8, 7, 6}; 
byte colPins[COLS] = {5, 4, 3}; 

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {
  Serial.begin(9600);
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    Serial.println(key);
  }
}

## 4. Operating Instructions

• Single Key Entry: Press the desired button firmly. The “tactile” click confirms the connection has been made.

• Multiple Key Presses: This module does not support “n-key rollover.” Pressing multiple keys simultaneously may result in “ghosting,” where the controller registers an incorrect third key.

• Cleaning: Use compressed air to remove dust between the buttons. If keys become “sticky” electronically, use a drop of 90% Isopropyl Alcohol on the switch and press it several times while powered off.

## 5. Troubleshooting