Keypad Circuits
Page 4
Key Pads:
#'s - C D - I
K - L M - Z
Last Updated on:
Wednesday, November 29, 2017 05:40 AM
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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Scheme improves on low-cost keyboard - 30-Oct-03 Issue of EDN You can
easily improve on a previous Design Idea 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..... [Design Idea by Martin O'Hara, Telematica Systems Ltd,
Cranfield, Bedfordshire, UK] |
Security Circuit 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..... EDN is
migrating links. This link is not verified. Search the "title" + "EDN" for new
link. |
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Security Keypad - 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. (11/04) |
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. (added circuit 5/06) |
Ser-Key 10-Key Serial Keypad Encoder - (electronic circuit added 4/05)
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Single-wire keypad interface frees microcontroller-I/O pins - 31-Mar-05
Issue of EDN Using this interface topology, you can reduce the number of keypad
interface wires to just one and thus save critical microcontroller I/O ports.....
[Design Idea by Israel Schleicher, Prescott Valley, AZ; Edited by Brad Thompson] |
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..... [Jonathan A. Buzzard] |
TB056: Demonstrating the *set_report* Request: With PS/2® to USB Keyboard Translator
Example - Microchip Application Note Published 4-May-04 (app note
added 2/06) |
Touch Keypad - 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.....(circuit added 08/08/08) [Luhan
Monat - Mesa Arizona] |
Two-wire, four-by-four-key keyboard interface saves - 08/17/06 EDN-Design
Ideas.....You can use a microcontroller that includes an ADC to design a two-wire-plusground
keyboard interface. For example, you can use a resistive voltage divider to identify a
pressed key (Reference 1). A microcontroller’s integrated ADC typicallyou can use a
microcontroller that includes an ADC to design a two-wire-plusground keyboard
interface. For example, you can use a resistive voltage divider to identify a pressed
key (Reference 1). A microcontroller’s integrated ADC typically..... [Design Idea by
Stefano Salvatori, University of Rome, Rome, Italy; and Gabriele Di Nucci, EngSistemi,
Rome, Italy] |
White LED driver backlights LCD and keypad - 13-Nov-03 Issue of EDN
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..... [Design Idea by Fabien Franc, Catalyst Semiconductor,
Sunnyvale, CA] |
White LED driver provides 64 step logarithmic dimming - 10-Jun-04 Issue of
EDN 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..... [Design Idea by
William Hadden, Maxim Integrated Products, Sunnyvale, CA] |
Wired USB Keyboard - (application / block diagram added 6/07) |
XY Keypad uses µC'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,..... [Design Idea by James Mears, National Semiconductor, Tacoma, WA] |
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Key
Pads: #'s - C
D - I K - L
M - Z |
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