Five-Digit Alarm KeypA - D - This is an enhanced 5 digit keypad which may be used with the Modular Alarm System. This switch will suit the Modular Burglar Alarm circuit. However, it also has other applications. The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13 terminals. The matrix type with 7 terminals will NOT do. Choose the five keys __ Designed by Andy Collison
FM Morse Code Keyer - Many no code Technician class amateurs who are struggling to learn 5 WPM code simply do not have any avenue to get the necessary on the air practice. Figure 1 is a simple circuit which will generate a 700 Hz tone into any FM transceiver allowing an amateur to practice CW with another amateur on a 2 meter simplex frequency __
Four Digit KeypA - D - This is an enhanced 4 digit keypad which may be used with the Modular Alarm System __ Designed by Ron J.
Four-Bit µP's A/D Converter Decodes Keypad's Input - 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 provid__ Circuit Design by Ryoden International Shanghai Ltd, Shanghai, China
Four-Digit Alarm Control KeypA - D - Alarm Control Keypads: 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. __ Designed by Ron J.
Four-Digit Keypad Controlled Switch - Universal Keypad-Controlled Switches: 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 relaybut you can use a multi-pole relay if you wish. __ Designed by Ron J.
Four-Digit Keypad Controlled Switchdb - This is a universal version of the Four-Digit Alarm Keypad. I have modified the design to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. It also means __
Greg is Chillin' With 50 Cent on His Tricked-Out Keyboard - 18-Jul-05 -Design News: For Greg Ruhlander's complete instructions on how to build your own computer keyboard with integrated am/fm radio, click here . Unable to function without his trusty portable am/fm radio at his side-especially while working-Greg hit upon the idea of integrating it directly into his computer's __ Gadget Freak
IBM PC Keyboard to Palmpilot Interface Why would you want to interface the Keyboard? The IBM keyboard can be a cheap alternative to a keyboard on a Microprocessor development system. Or maybe you want a remote terminal, just couple it with a LCD Module. Maybe you have a RS-232 Barcode Scanner or other input devices, which you want to use with existing software which only allows you to key in numbers or letters. You could design yourself a little box to convert RS-232 into a Keyboard Transmission, making it transparent to the software __ Designed by Craig Peacock
Improve On Low-Cost Keyboard - 10/30/03 EDN-Design Ideas You can easily improve on a previous Design Ideasto 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 val__ Circuit Design by Martin O'Hara, Telematica Systems Ltd, Cranfield, Bedfordshire, UK
Interfacing a 4X4 Keypad to a BS2 using a 74922 Encoder Chip - This is a pretty basic project, I had a little trouble understanding how the 74922 worked but I after an hour or so of looking at the data sheet and using my logic probe I understood completely. Here is a brief description of how the 74922 works. The chip scans the keypad waiting for a keypress. When a button is pressed pin 11 of the 74922 goes high. Then a 4 bit binary number corresponding to the button press is sent to pins 14-17 of the IC __ Designed by shaunwilson19 @ yahoo.com
IR Terminal, Remote - 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 Monat-Mesa Arizona
Keyboard Data Acquisition System is Cheap & Simple - 02/03/00 EDN-Design Ideas The most important criteria of a data-acquisition system for college science laboratories are simplicity and price rather than precision or speed. The data-acquisition system in Figure 1 offers adequate precision of less than 0.5% and speed of 1 Hz to replace the outdated laboratory chart recorder in studentCircuit Design Tom Lyons Fisher, Juniata College, Huntingdon, PA
Keyboard Data-Acquisition System Is Cheap & Simple - EDN-Design Ideas December 31, 1969 The most important criteria of a data-acquisition system for college science laboratories are simplicity and price rather than precision or speed. The data-acquisition system in Figure 1 offers adequate precision of less than 0.5% and speed of 1 Hz to replace the outdated laboratory chart recorder in student laboratories. You can install the system in 5 sec, operate it with a single toggle switch, and construct it for approximately $40. The only additional equipment necessary is a computer running Excel and an ATbus (not Universal serial bus), keyboard. __ Circuit Design by Tom Lyons Fisher, Juniata College, Huntingdon, PA
Keyboard links to microcomputer through one-wire interface - 09/29/05 EDN-Design Ideas Simplified, improved interface cuts keyboard I/O cost__ Circuit Design by Israel Schleicher, Prescott Valley, AZ
Keyboard Wedgie - A "keyboard wedge" is a device for connecting between a keyboard and computer for automatically entering information, as though it were typed, avoiding the need for a special program to be running on the computer. The Keyboard Wedgie is a lightweight version for entering binary data into a spreadsheet or other program. It uses a small PicAXE processor to measure a voltage with 10 bits resolution and enter that value, in binary, into a desktop computer, typically into a spreadsheet program. It replaces either an old serial keyboard or a USB keyboard and will work with another keyboard attached, in most cases. This abbreviated device can only punch three keys, the "0, " "1, " and "enter" keys, just enough to enter a binary value into sequential cells in a spreadsheet or lines in a text editor. Since the Keyboard Wedgie simulates key presses, it will work with just about any keyboard system without any knowledge of the signaling protocols. It, after all, just presses buttons. __ Contact: Charles Wenzel of Wenzel Associates, Inc.
KeyLock - Press four keys in specific order, and relay will turn on for about to 5 seconds and that is it. But first you must memorize your code following this way: press and hold button (button on pin 3) , so long until Led goes ON. Now, when. __ Designed by © Ivica Novakovic
Keypad Access - Dual programmable keypad code lock. Open electrical doors with your secret code only! __ Designed by Michel Bavin
Keypad Circuit-with Parallel Code Entry - Universal Keypad-Controlled Switches: This is a universal four-digit keypad-operated switchwith a difference. Instead of entering the security code one number at a timethe four keypad buttons must be pressed simultaneously. Split the code between two separately located keypadsand two people will have to be present in order to operate the switch. Each person can have a different three-digit code. __ Designed by Ron J.
Keypad Combination Lock - A digital combination lock using a push button keypad. The combination can be changed and the lock has an entry delay. __ Designed by Andy Collison
Keypad Control for Multiple Appliances - This circuit employs DTMF technique to switch on/off up to ten appliances. It can be modified to operate up to 100 appliances using the same keypad. The controller uses telephone-type keypad with...___ Electronics Projects for You
Keypad Controlled Switch No.2 - Universal Keypad-Controlled Switches: This is a simplified version of the 4-Digit Keypad Controlled 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.
Keypad Electronic Door Release - 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 __ Designed by Ron J.
Keypad Encoder ComMands Tape Transport - 09/02/96 EDN-Design Ideas Sometimes, using a component in an application other than its intended application can yield savings in design time, component count, cost, and complexity. The MM74C922N, originally designed to detect, debounce, and encode 16-key switch matrices, contains most of the elements needed for a full-function magnetic-tape-transport motion-control circuit (Figure 1). The IC replaces more than nine packages of CD4000 flip-flops and random logic and provIdeas everything but a motion-sensing circuit. __ Circuit Design by James Mears, National Semiconductor Corp, Tacoma, WA
Keypad engine immobiliser - There's no need for a hidden "kill" switch.___ SiliconChip
Keypad Operated Switch No.2 - 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
Keypad Project - Interfacing a 4X4 keypad to a BSII using a 74922 encoder chip. This is a great project for data entery, security keylocks, and much more. Only uses 5 I/O pins on the Stamp. __
Keypad sequence activates relay - 10/12/00 EDN-Design Ideas Today, it seems that µPs assume even the easiest tasks, such as activating a relay(for an alarm or access control, for example]via a keyboard command. However, a simpler and less expensive solution is available(Figure 1). Moreover, the method does not entail programming and the concomitant, almost inevitable,__ Circuit Design by JB Guiot, DCS AG, Allschwil, Switzerland
Keypad Decoder - decodes and generates a standard 4x3 keypad to produce a 4-bit binary output. __ Contact: P. Townshend EduTek Ltd
Key-Reading Saves I/O Pins - 6-Mar-03 EDN-Design Ideas Amplifiers perform precision divide-by-2 circuitSome microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses. Some alternative ways to read keys yieldfree pins. First, consider some ways to effect key reading. Table 1 presents a comparison of four methods with references to circuit configurations(figures 1, 2, 3, and 4]__ Circuit Design by Gustavo Santaolalla, Digital Precision Systems, Buenos Aires, Argentina