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.

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How to Use ESP32's Input Only Pins with Keypad Library

I am tring to use 1x4 keypad with ESP32. I am using this keypad and this ESP32 (30 pins) also I am using this keypad library I have only free those pins 14,15,34,36 (VN) ,39 (VP) on ESP32. the others ...
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Problem with TTP229-BSF using Arduino Uno

I'm trying to use a 16-channel capacitive touch sensor named TTP229-BSF with an Arduino Uno. I use the following code it works correctly when i touch directly but when i place two 4 mm plexiglass pads ...
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strange behavior of 3x4 keypad [closed]

hi i tried to use the keypad.h library for sending a pressed key to serial port of esp32 by Arduino platform but it didn't work and it only detected rows. so i tried to write a function for running ...
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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 ...
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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 ...
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4 votes
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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 ...
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Keypad interfacing on microcontroller

I am extremely new to dealing with microcontrollers and programming in general. The picture below is a circuit board using a PIC18F4520 microcontroller. As of now, I am focused on the 4x4 matrix ...
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2 votes
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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 ...
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Make a faux call on old 1950s touch tone phone [closed]

I have a 1950s ice cream shop and just bought a vintage touch tone phone. It works if I connect it to a phone line but I won't be doing this. What I really want to do is pre-record messages that will ...
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Error in LCD while interfacing with ATmega 32

I am trying to interface a normal keypad and LCD .where for example if i press '1' in keypad it will show 'one' in the display . if i press '=' it will show 'EQUAL' in Display . i developed below code ...
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Touch pad Document

I tear down one touch pad and wonder what technology they used. I am sharing picture of it. Any one know what is used for touch sense ? (my guess is capacitive). I am planning to design one by myself. ...
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Combining interrupts and debouncing on a keypad

I would like to interrupt a program when a key is pressed on a keypad, and figure out which key has been pressed. I do not care much for ghosting effects, this is supposed to be operated with one ...
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Setting Pulldown on the PMOD Pins (Nexys A7)

Ive created a keypad scanning project with Verilog. The waveform works great! But it did not work in practice. Through troubleshooting I found that it will work if I add external pulldown resistors to ...
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Problem with Keypad exercise on STM32 (Nucleo-F103RB)

I try to learn STM32 MCU programming and at the beginning I'd like to mark, that't I'm totally begginer in it, so please forgive me some mistakes (also language mistakes). So I'm using STM32F103RBT6 (...
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Using an MCP23008 IC with a 4X4 matrix keypad on a Raspberry Pi [closed]

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 ...
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Raspberry Pi sometimes detects wrong keypad number

I am using a 3 x 4 Sparkfun keypad connected to a Raspberry Pi. The issue I am facing is that 40% of the time wrong keypad numbers get detected after pressing the button. For example, when I press &...
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Resistor Keyboard Vs Matrix Keyboard

I'm part way through my prototye macro keyboard which currently consists of 4 keypads with 16 keys on each - so 64 keys in total. The method I'm using is the 3 wire, resistor based one.R1,R2,R3 and ...
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Keypad schematic - is it correct?

What do you think of this schematic for my Arduino keypad? Are the diodes pointing the right way? I will make col1 "high" and then check pins ...
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Why are my keypad pins more than total number of columns and rows?

I have newly bought the following keypad with 4 rows and 3 columns from a not well-recognized shop. But I am wondering, why it has 10 pins in spite of 7 pins (total number of rows and columns). ...
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Interfacing 4*4 keypad avr-gcc [duplicate]

I have this function for a 4x4 keypad: ...
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2 answers
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avr-gcc keypad interfacing code problem

I have this function to read key press from a 4x3 key-board: ...
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NVG compatibility LED Lights

For an avionics application I need to make a keypanel which has NVG compatible LED lights behind its keys. I am trying to understand how does the NVG compatibility (Night vision Goggles) relates to ...
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keypad debouncer configuration RC Value

I have keypad with for buttons and common signal connected to ground.. I noticed two configuration for debouncing as shown bellow.. Question: - Will the both configuration work correctly? when ...
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Keypad saved shifting display using Verilog

I'm designing a number exchange module, and so far I've been able to make it display on Seven Segment Display (S-S-D), like if I press 0 it shows 0... etc. I'm using 2 sets of 4-bits S-S-D (Common ...
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How do you make crossing wires not connect in EAGLE? [closed]

I am brand new to PCB designing (started yesterday) and am doing it as a fun little side project. My goal is to produce a working PCB that has a very basic function. My problem is this: I have no ...
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2 votes
3 answers
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Clean/repair/replace the carbon pill of a rubber keypad

I have several devices (calculators, remote controllers, …) with rubber keypads where some keys are dysfunctioning. As I understand it, this is because of the carbon pill since things work fine if I ...
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how rubber keypad works [closed]

Press on the keyboard, how does he connect the circuit of this key? Two thin films, coated with conductive rubber circuit, with a thin film in the middle, with holes, used to isolate two thin films ...
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how to mount a flat keypad on a panel

Flat Keypad or Membrane Keypads are cheap and beautiful Keyboad that can be used in systems. but the question is how can they be mounted in a box or panel?
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I designed a touch PCB keypad what can I do for silking and covering

I want to design a custom keypad for my board. I put my board in a Plastic box 15cm x 19cm and the box has a simple box door. I want to put a keypad and a 2x16 character LCD in this door to control ...
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8051 program not processing keypad matrix correctly

I made myself a small PCB (measuring about 6cm by 5cm). This is what is supposed to happen: Upon power-up, the LED goes red to indicate that the unit is ready for input. I then press any key down (...
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1 vote
1 answer
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Silicone rubber keypad PCB design

I have a question regarding PCB design and rubber keypad contacts. I did this circuit for prototyping a piano keybed but some contacts seem to be unstable: when pressed it switches from 0 to 1 ...
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Learning the Art of Electronics - keypad schematic

The image below is an extract from the schematic for the keypad referred to on page 620 of LAoE. What does the symbol connecting switch S4 to pin 11 of U7 and connecting pins 6 and 11 of U7 mean in ...
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Learning the Art of Electronics - keypad

Has anyone found ordering information or the schematic referred to on Page 620 of Learning the Art of Electronics? Page 620 of LAoE says, "The keypad is not a standard commercial part. See Appendix E ...
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Connect 4x4 keypad to esp8266 I2C

I want to connect 4x4 keypad to nodemcu, but some of the pins on board are already in use. For LCD I have used I2C backpack, and have an extra lying around. Can it be used to connect keypad to nodemcu ...
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Altium keypad footprints custom pad DRC errors

I've created a rubber keypad switch footprints which is a simple contact pad design. First I used arcs and tracks to get a outline and then converted them to top copper region(two seperate regions). ...
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Wake up ESP-32 using matrix keypad

I want to realize a wireless keypad using ESP-32 and a matrix 4x3 keypad, connected via Bluetooth Low Energy to a master unit. I want to use deep sleep mode of ESP-32 when the keypad is not used but I ...
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11 votes
3 answers
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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 ...
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Weak key fob signal

I have a VW Golf 5 from 2004. I have bought it about 4 years a go. I have 2 pairs of keys. With the first one, I could never open the car remotely. The second one worked quite well but its range ...
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2 votes
2 answers
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Would it be possible to replace/wire the buttons on a keypad with buttons from this old phone?

Sorry I know the title's a little rough, but hopefully some pictures will help I have this keypad Here it is the front panel removed (note that each metal node is a button in itself, you can press ...
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9 votes
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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 ...
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Reducing the number of pins needed to read a 12-key keypad where the buttons are grounded?

Unfortunately, I'm not sure what the right question is; I'have a 12-key keypad. I wanted to utilise a matrix based approach, except that they all seem to be connected in such a way, that they're ...
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MULTICOMP MCAK304NBWB KEYPAD: What are the pins 8 and 9 connected to?

According to the datasheet, the 7 pins are from the 4 rows and 3 columns. What are the other 2 pins connected to ? The image shows 9 pin outs.
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-3 votes
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Can I achieve debounce using a zener diode?

I am interfacing a 4x3 keypad with LPC1778 using GPIO pins. These pins are 5V tolerant. Can I use zener diodes in the debouncing circuit? Can I use zener diodes like this?
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15 votes
1 answer
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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 ...
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Detect position of walkers along a path using IR transceivers

I am working on a project that the position of people walking along a path needs to be known. I'm a hobbyist so I don't know what options I may have. I want to use IR sender and receivers to ...
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Calculator with MSP430 in Assembly Language

I am programming a calculator in assembly language with the MSP430g2553. I have a 4x4 membrane keypad and an 2x16 LCD. I already can display numbers in the LCD with the keypad. The issue is that the ...
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col not declared issue{Verilog}

I am having a problem here can't make this code compile. It is a 4x4 keypad scanner with a 20ms debouncer. It gives error "Error: 'col' has not been declared" Any suggestion? ...
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vhdl code interfacing keypad with fpga

...
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4x4 keyboard matrix not generating unique keycodes

I have a 4x4 keybord matrix fsm scanner but it generates only high keycode setting all last 4 bits to 1 and second and fourth digits to high. Is there anything wrong in my code here? ...
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How to initiate a call on a GSM module from DTMF tones

Can someone tell me if it is possible to make a call from a GSM module using only the DTMF tones that a keypad puts out? If not, can someone explain how I would make the call using only the keypad, ...
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