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Keypad Circuits

Key Pads:   #'s - D      E - K      L - Z

Last Updated: October 24, 2017 02:55 PM

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

LCD 2x16 characters &  4x4 keypad assembly example -  Connect some 2x16 characters LCD display and 4x4 keypad with AVR microcontroller __ Designed by Jerry Meng

Low Cost AT Keyboard Translator -  This Low-cost project takes the complex scan codes from a PC keyboard and spits out standard ACCII codes.  It's just the shot for use with the BASIC stamp and PIC series of microcontrollers but has lots of other uses as well.___ SiliconChip

Low-power keypad consumes only 100 nA -  24-Jan-02 EDN-Design Ideas Often in the use of products with keypads, one orkeys become "stuck" or are being pressed.  For example, a cell phone in the bottom of a purse or in a hip pocket could have one orof its keys inadvertently pressed and held down for a considerable period.  Depending on the circuit design and implementation of the keypad interface, this condition could cause excess current to flow,__ Circuit Design by Mike Mitchell, Texas Instruments, Dallas, TX

MIDI-Mate: a MIDI Interface for PCs -  Easy-to-build project connects to your PC's sound card to provide full MIDI input and output ports.___ SiliconChip

More-MIDI -  A low-cost MIDI expander box___ SiliconChip

Novel Idea Implements Low-Cost Keyboard -  3-Apr-03 EDN-Design Ideas Many applications that use a microcontroller also use a keyboard.  If your application uses a relatively powerful microcontroller, you can use several free I/O pins or an unused input with an ADC to effect an easy keyboard connection.  But, if the microcontroller in your system has too few free I/O pins and no on-chip ADC, you can be in trouble__ Circuit Design by Jean-Jacques Thevenin, Thomson Plasma, Moirans, France

One-wire keypad interface frees microcontroller-I/O pins -  03/31/05  EDN-Design Ideas Using this interface topology, you can reduce the number of keypad interface wires to just one and thus save critical microcontroller I/O ports__ Circuit Design by Israel Schleicher, Prescott Valley AZ

PS/2 Keylogger based on PIC12F675 -  This is a keylogger based on PIC12F675 with 64K eeprom (24LC512).  When keylogger is connected between PC and keyboard it will record every keypress to memory.  By pressing a button recorded data will be sent back to PC so user can read it.  No need __

Remote Infrared Terminal -  This unit provide 2 way IR communications using a numeric keypad and an LCD display.  Data is sent and recieved in ASCII with no regard to what the data means to any particular device __ Designed by Luhan MonatMesa Arizona

RS-232C port scans remote keypA - D -  12/04/97 EDN-Design Ideas In many embedded or control applications, you might prefer to use a small, customized keypad with your PC-based system rather than a full-fledged alphanumeric keyboard.  You may also need to locate the keypad some distance from the system hardware.  If you have__ Circuit Design by SK Shenoy, NPOL, Kochi, India

Scanning 7-Segment & KeypA - D -  Since the output buffer ofP1 can sink 20mA (each output pin, but maximum IOL for all outputs was limited at 80mA) , thus we can use P1 to drive LED display directly.  As shown in the circuit, Two common-anode 7-segment LEDs are connected to P1 with 180 Ohms current limiting resistor.  Each segment of two LED __ Designed by Wichit Sirichote

Scheme improves on low-cost keyboard -  30-Oct-03 EDN-Design Ideas You can easily improve on a previous Design Ideas to produce a slightly simpler resistor arrangement with better timing balance between switches, using a single resistor value(Reference 1, Figure 1].  The use of a single resistor value, RS, in a series chain for the switch resistors gives the timing parameters a simpler format and should reduce bill-of-materials cost__ Circuit Design by Martin O'Hara, Telematica Systems Ltd, Cranfield, Bedfordshire, UK

Security Eschews Sophistication -  05/26/94 EDN-Design Ideas Because of the many states involved in implementing sequential combination locks, most designers use a microcontroller or a PLD.  But for those die-hard discrete designers who don't want to bother with debugging programs, here's a dead-simple circuit that verifies a security code's entry from a 10-digit keypad__ Circuit Design by Design Idea EDN Design Idea -- 05/26/94  I-Cheng Chen, AEG, Ajax, ON, Canada

Security KeypA - D -  This Electronic Code Lock uses a 12-keys keypad is used to enter a password and open an electrick lock or any other device with a signal.  Uses an 8-pin PIC 12F629.   __ Designed by Jose Pino

Security Keypad II -  An improved version that can be used on security vaults, Doors with electric latches, Alarms, Safety devices and many other uses.  It uses an HITACHI LCD (16x1 or 8x1) and a matrix keypad.  The HEX code is available for 16F84A and 16F628.   __ Designed by Jose Pino

Ser-Key 10-Key Serial Keypad Encoder -  Schematic only, no circuit description __ Designed by Reynold's Elec

Simple Circuit keypad operated switch -  I have modified the design to reduce the complexity of the circuitand the number of components required.  As a resultthe code is somewhat less secure.  However, there should be lots of situations where it will still be adequate.   __ Designed by Ron J

Single-wire keypad interface frees microcontroller-I/O pins -  31-Mar-05 EDN-Design Ideas Using this interface topology, you can reduce the number of keypad interface wires to just one and thus save critical microcontroller I/O ports__ Circuit Design by Israel Schleicher, Prescott Valley, AZ

Sun Type 5 keyboard on the PC -  Many people have dreamed of having their Sun Type 5 keyboard attached to their PC.  Now with this adapter, it is finally possible.  Because the standard Sun keyboards use TTL RS232 at 1200 bps to talk to the Suns, it's relatively easy to make them talk to any non-Sun computer by converting this to true RS232.  However PC's don't understand keyboards hooked up to serial ports without special drivers.  While such drivers do exist you will still need to keep a PC keyboard about if you want to change the BIOS setup etc __ Designed by Jonathan A. Buzzard

Touch sensistive touchpA - D -  This board layout was created using the SOIC version of a PIC16F627A without drawing the usual schematic first.  Most of the part values are etched on the Layout.  The SIP resistor packs I used are 10k ohm, some experimentation with this value may be useful __ Designed by Luhan Monat-Mesa Arizona

Two wire 4 by 4 key keyboard interface saves power -  08/17/06 EDN-Design Ideas Resistor matrix and microcontroller encode keypadYou can use a microcontroller that includes an ADC to design a two-wire-plus-ground keyboard interface.  For example, you can use a resistive voltage divider to identify a pressed key   (Reference 1).  A microcontroller's integrated ADC typically presents an input resistance on the order of hundreds of kilohms, and, for adequate accuracy, its keypad divider should comprise relatively low-value resistors of 10s of kilohms.  __ Circuit Design by Stefano Salvatori, University of Rome, Rome, Italy, and Gabriele Di Nucci, EngSistemi, Rome, Italy

Universal 4 Digit Keypad Operated Switch -  This is a universal version of the Four-Digit Alarm Keypad.  I've modified the design of the output sectionto free up the relay contacts.  This allows the circuit to operate as a general-purpose switch.  I used a SPCO/SPDT relaybut you can use a multi-pole relay if it suits your application.   __ Designed by Ron J

Water & vandal-proof keypad uses piezoelectric disc as sensor & buzzer -  04/21/14  EDN-Design Ideas An ingenious and low-cost method to create a rugged UI.  This design was done to get a sealed keypad for very wet environments (in my particular case, showers for swimming pools).  The keypad needed to be able to detect slight pressure on a stainless steel plate 0.4mm thick.  Apart from water protection, the solution offers an esthetical finish, as the user side is absolutely flat, with nothing visible other than the silkscreened print.  Another advantage of this type of keypad is that it is vandal-proof__ Circuit Design by Francesc Casanellas

White LED driver backlights LCD & keypA - D -  13-Nov-03 EDN-Design Ideas Designers widely use white LEDs to backlight color LCDs and keypads in handheld devices, such as cell phones, MP3 players, GPS navigators, and PDAs.  Their spectrum and brightness represent near-ideal light sources.  One possible configuration for a phone or a phone/PDA combination is to have a group of three LEDs to light the display and six LEDs for the keypad__ Circuit Design by Fabien Franc, Catalyst Semiconductor, Sunnyvale, CA

White LED driver provides 64 step logarithmic dimming -  10-Jun-04 EDN-Design Ideas The circuit of Figure 1 is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels.  The circuit drives as many as four white LEDs from a 3.3V source and adjusts the total LED current from 1 to 106 mA in 64 steps of 1 dB each.  The driver is a charge pump that mirrors the current ISET(sourced from IC3's SET terminal] to produce a current o__ Circuit Design by William Hadden, Maxim Integrated Products, Sunnyvale, CA

XY Keypad uses C's Serial Port -  10/10/96 EDN-Design Ideas Interfacing an X-Y keypad to a microcontroller usually uses a parallel port of 8 bits or more.  But with the circuit shown in Figure 1, a more efficient interface using a microcontroller's serial port reduces the number of connections required from eight to three.  This interface uses the MM74C922N, a National Semiconductor keypad encoder,__ Circuit Design by James Mears, National Semiconductor, Tacoma, WA

Sense multiple pushbuttons using only two wires -  Sense multiple pushbuttons using only two wires figure 1Keyboards and numeric keypads often provide the user interface for electronic equipment, but many applications require only a few pushbuttons. For those applications, you can monitor multiple pushbuttons over a single pair of wires (Figure 1). __ Designed by Bernhard Linke, Maxim Integrated Products Inc, Dallas, TX

Keypads:   #'s - D      E - K      L - Z


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