Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [keypad]

Keypads are typically small 3x4 or 4x4 membrane button matrixes, used for phones or other devices needing numerical input. Similar to keyboards.

Keypads are typically small 3x4 or 4x4 membrane button matrixes, used for phones or other devices needing numerical input. Similar to keyboards.

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Studying the PCB of a 70s calculator. What were they thinking?

I've been studying the PCB from an ELSI 8002 calculator from 1974. I'm thinking of repurposing the case for a project, though now that I've fixed it (by re soldering the battery connectors) I don't know if I can bear to pull it apart. (sniff) Maybe,…
futurebird
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How does the telephone's keypad work?

I disassembled some old telephone and mobile phone. Every keypad is different, and yet, all of them have those "spirals" (see the image below) under the button or something similar. What I don't understand is how those "spirals" can put in contact…
Tripola
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Silicone Keypad Design Problems

My device uses a silicone keypad to detect a key press rather than a physical button. After setting up, it works smoothly, even without applying much pressure to the keypad. However, after a while ( say 2 months), you will need to apply much…
Paul A.
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A good circuit for a large number of push button inputs?

I'm planning to build a kid-friendly "universal remote" so the kids can turn on and off a myriad of IR-controlled devices with one or two easy presses... The remote is going to have maybe 20 big chunky buttons which, when pressed, with send the…
Brad
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4x4 matrix keypad interface with microcontroller

I am extremely new to microcontrollers and PIC programming. I need help in understanding how a 4x4 matrix keypad works. I know the 8 pins are used to determine which of the keys are pressed by the user but other than that, I am lost in the concept…
Fiidisks
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Using the right pins for keypad

I am using msp430g2553 microcontroller and a 4x4 HC543 keypad. I am using Energia IDE. I have connected the keypad from pin 2 through 9. My code is as follows: #include const byte ROWS = 4; //four rows const byte COLS = 4; //four…
AdityaGovardhan
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4x4 keypad to Microcontroller

I have 8pin 4x4 keyapd, and i want to connect it to my microcontroller, I've search over the net but i can't see its pin configuration. I have a problem connecting it because of that can someone help me. I have a picture of the keypad and pin…
NewInEverything
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Replacing a keypad on DYMO LetraTag

I'm rebuilding my label printer to become an Internet service using an ESP8266. It's a fun project, never mind the usefulness. The keypad will be removed and instead my MCU emulates keypresses. The keypad has: 8 pins that always have 3.2V (red…
mikabytes
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avr-gcc keypad interfacing code problem

I have this function to read key press from a 4x3 key-board: uint8_t GetKeyPressed() { uint8_t r,c; KEYPAD_PORT|= 0X0F; for(c=0;c<3;c++) { KEYPAD_DDR&=~(0X7F); KEYPAD_DDR|=(0X40>>c); for(r=0;r<4;r++) { …
Danial
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Which schematic is better for keypad connection to an MCU?

I have this three keypad connection sketches, all of which i've seen in various application, and some i've also used, but i want to know if there is any advantage of one over the other. The keypad will be connected directly to DIO pins of a PIC…
TiOLUWA
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Interfacing a keypad with a microcontroller

I am using a PIC16F877A, running at 20 MHz. I have two paralleled, 3 columns, 4 rows keypad. My setup is as follows: KR1 to KR4 are rows, KC1 to KC3 are columns, and they all go to the microcontroller. In the program, rows are set as digital…
abdullah kahraman
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MPS430 Launchpad Keypad

I tried to use my MSP430G2553 launchpad with a keypad…
Cagurtay
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Theory of operation of MM74C922N

I have been studying the datasheet of the MM74C922N , a 4x4 matrix keypad, but I cannot seem to understand how it works under the 'Theory of Operation'. I know it outputs a 4-bit binary code depending on the key pressed, but other than that, I don't…
BeatriceUK
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Membrane switch - 39 switches - 11 inputs and only 6 outputs to processor

I have reverse engineered a membrane keypad that connects to a microprocessor. I have no info on the keypad but it has 39 switches. The output of the keypad is an 11 way ribbon cable. This goes to a small PCB with resistors and diodes - nothing…
mike james
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Using an MCP23008 IC with a 4X4 matrix keypad on a Raspberry Pi

I want to be able to free up the native GPIO pins on my Raspberry Pi Zero. I know the MCP23008 gives me 8 extra pins, but I can't seem to find any resources on using the additional pins with a 4X4 matrix keypad.
Pekkle Juice
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