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Keypad Circuits   Page 1
Key Pads:  #'s - C      D - I      K - L      M - Z
Last Updated on: Friday, October 03, 2014 10:37 AM
 


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

A Current Limiting Bench Power Supply -  This is a 1-amp variable-voltage PSU. It adjusts from about 3v to 24v: and has the added feature that you can limit the maximum output current.  This is invaluable when (for example).... [Circuit Designed by Ron J.]
µC implements Pushbutton Light Dimmers -  06/18/98 EDN-Design Ideas.....A project required building a synchronous-demodulator circuit to track a line drawn on paper.….File contains several circuits, scroll to find this one..... [Design Idea by William Grill, Riverhead Systems, Littleton, CO]
µC Provides Wireless Keypad Control -  10/08/98 EDN-Design Ideas.....Portable systems, such as telephone handsets, make extensive use of low-dropout (LDO]regulators. se components provide noise-sensitive parts with a stable power-supply line.....Scroll to find this specific article..... [Design Idea by Lloyd Khuc, Motorola Inc, Austin, TX]
2 Way IR Term -  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.
…..... [Luhan Monat - Mesa Arizona]
3 wire 4 by 4 key keyboard interface saves power -  08/17/06 EDN-Design Ideas.....Resistor matrix and microcontroller encode keypad..... EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
4 Digit Keypad -  (electronic design added 9/02)

4-Digit Alarm Control Keypad -  This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Pressing a single key will energize the relay. Entering the Four-Digit code of your choice will de-energize it.  (Circuit design added 08/08/08)
4-Digit Keypad Controlled Switch -  This is a Universal version of the Four-Digit Alarm Control Keypad. I have modified the design to free up the relay contacts.  This allows the circuit to operate as a general-purpose switch. I've used a SPCO/SPDT relay, but you can use a multi-pole relay if you wish.  (Circuit design added 05/06/07)
5 Bit µP's A/D Converter Decodes Keypad's Inputs -  10/13/94 EDN-Design Ideas.....Fig 1 shows a Mitsubishi M50927-XXXSP/FP 4-bit microcontroller decoding a 4×4 keypad using only four digital I/O lines instead of eight. Saving four of a 4-bit µC's precious I/O lines couild be significant.  4-bit µC's ADC provides  key to  savings.  µC's output lines, F1 through F4, energize  keypad's column lines one at a time via 74HC4049 buffer/driver..... [Design Idea by Ryoden International (Shanghai) Ltd, Shanghai, China]
5-Digit Alarm Control Keypad -  This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit code, will energize the relay. Entering the Full Five-Digit code, will de-energize it.  (Circuit design added 08/08/08)
A 4-Digit Alarm Control Keypad -  This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Pressing a single key will energize the relay. Entering the Four-Digit code of your choice will de-energize it…. [Designer Ron J.]
A 5-Digit Alarm Control Keypad -  This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit code, will energize the relay. Entering the Full Five-Digit code, will de-energize it.  (Circuit design added 08/08/08) [Circuit Designed by Ron J.]
A Decimal to BCD Decoder -  This circuit will take the input from a keypad with up to 16 buttons, and convert it into a ''latched'' BCD output….. [Circuit Designed by Andy Collison]
A Transformerless Power Supply -  This circuit will supply up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance, so it doesn't generate very much heat. The circuit was designed to provide a cheap, compact power supply for Cmos logic circuits that require only a few milliamps. The logic circuits were then used to control mains equipment, using an optically-isolated triac..... [Circuit Designed by Ron J.]
Alarm control keypad -  The IC is a quad 2 input "AND" gate, a CMOS 4081. These gates only produce a HIGH output, when BOTH the inputs are HIGH. When the key wired to 'E' is pressed, current through R1 and D1 switchs Q5 on.The relay energises; and Q5 is 'latched on' by R8. Thus, the Alarm is set by pressing a single key,say one of the two non-numeric symbols..... [Ron J.'s circuit
An Add-On Current Limiter For Your PSU -  This circuit allows you to set a limit on the maximum output current available from your PSU. It's very useful when…. [Ron J.'s circuit]
An Alarm Power Supply With Battery Back-up -  This Power Supply is suitable for the Modular Burglar Alarm. However, it has other applications. It is designed to provide an output of 12-volts, with a current of up to 1-amp. In the event of mains failure, the back-up battery takes over automatically. When the mains is restored, the battery recharges.... [Circuit by Ron J.]
AN528: Implementing Wake-Up on Keystroke -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN529: Multiplexing LED Drive & 4x4 Keypad Sampling -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN552: Implementing Wake Up on Keystroke -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN557: Four Channel Digital Voltmeter with Display & Keyboard -  Microchip Application Note Published 27-May-05.....[App Note]
AN-734: MF2 Compatible Keyboard with COP8 MicroControllers -  National Semiconductor Application Note  (app note added 2/06)
AT89C2051/4051scanning 7 Segment Display & Keypad -  (circuit / schematic design added 6/06)
AVR 2x16 LCD & 4x4 keypad driver -  A very simple circuit to experiment with AT90S2313, 2x16 LCD display and 4x4 keypad. The clock based on 4 MHz crystal, but you can use anyone crystal between 1-4 MHz. The keys with the name "A", "B"....."F" are typed to the LCD with numbers 10-16. Because the AVR have only 15 I/O pins we are working the LCD display with 4-bit databus. The 4 resistors (10K) are to protect the AVR from the shortcuts as the coloumn of the keypad is change.....(circuits added 05/09)
Camera serializer/deserializer chip set reduces wire count for keypad -  28-Apr-05 Issue of EDN  Keypad interconnect needs just four wires..... [Design Idea by Wallace Ly, National Semiconductor Corp; Edited by Brad Thompson]
Connect a 2x16 characters LCD display to a 4x4 keypad -  Connect some 2x16 characters LCD display and 4x4 keypad with AVR microcontroller  (electronic design added 03/04/05)

Key Pads:  #'s - C      D - I      K - L      M - Z

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