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2-Wire Keypad Interface Using a 555 Timer. Part 1 Theory and Schematic - Keypads are a very commonly used input device in microcontroller-based systems. In a keypad, multiple switches are arranged in rows and columns so that they could be interfaced to a microcontroller with a minimum number of I/O pins. For example, a 12-key keypad is arranged in a 4×3 format, which allows to interface the 12 keys to a microcontroller with only 7 connections. __ Designed by Radio LocMan
4 Digit KeypA - D - This is an enhanced 4 digit keypad which may be used with the Modular Alarm System __ Designed by Ron J.
4 Digit Keypad 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.
4-Bit µPs A/D Converter Decodes Keypads 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
4-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.
4-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.
5 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
5-Digit Alarm Control KeypA - D - Alarm Control Keypads: This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit codewill energize the relay. Entering the Full Five-Digit codewill de-energize it. __ Designed by Ron J.
7 Segment Display & 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
A 4-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.
A 4-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.
A 5-Digit Alarm Control KeypA - D - Alarm Control Keypads: This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit codewill energize the relay. Entering the Full Five-Digit codewill de-energize it. __ Designed by Ron J.
A Current Limiting Bench Power Supply - Power Supply Circuits: 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) you power-up a project for the first time or soak-test a piece of equipment. __ Designed by Ron J.
A Decimal to BCD Decoder - Miscellaneous: This is a keypad circuit that will convert the decimal value of any keypad switchinto its BCD equivalent. __ Designed by Ron J.
A 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
Alarm control keypA - D - 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.
An Add-On Current Limiter for Your PS - U - Power Supply Circuits: This circuit allows you to set a limit on the maximum output current available from your PSU. It's very useful when you power-up a project for the first timeor carry out a soak-test. By setting an upper limit on the current available from your PSUyou can protect both your power supplyand any device connected to it. It offers a simple and cheap alternative to the Current Limiting Power Supply. __ Designed by Ron J.
An Alarm Power Supply with Battery Back-up - Power Supply Circuits: 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. __ Designed by Ron J.
AT89C2051/4051 Scanning 7 Segment Display & 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
AVR 2x16 LCD & 4x4 keypad driver - Connect some 2x16 characters LCD display and 4x4 keypad with AVR microcontroller __ Designed by © Vassilis Serasidis
Camera serializer/deserializer chip set reduces wire count for keypA - D - 28-Apr-05 EDN-Design Ideas Keypad interconnect needs just four wires__ Circuit Design by Wallace Ly, National Semiconductor Corp
Car Door Keypad using LIN network - Automotive, car and motorcycle electronic circuit diagrams / circuit schematics __
Connect a 4×3 matrix keyboard to a microcontroller using two I/O pins - 05/08/13 EDN-Design Ideas To connect a 4×3 keyboard requires seven digital I/O pins. This becomes a problem when the project is based on a low-pin-count MCU or when the MCU being used does not have enough free I/O pins. __ Circuit Design by Aruna Rubasinghe
Connecting AT90S2313 with LCD display 2x16 char & 4x4 keypA - D - Connect some 2x16 characters LCD display and 4x4 keypad with AVR microcontroller __ Designed by © Vassilis Serasidis
Data-Acquisition System Is Cheap & Simple - 12/31/69 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 rep__ Circuit Design by Tom Lyons Fisher, Juniata College, Huntingdon, PA
Decimal to BCD Convertor - This circuit will provide an output in Binary Coded Decimal from any of the input switches. The input switches may be expanded to 16 switches, providing a Hexadecimal to BCD conversion __ Designed by Ron J.
Decimal to BCD Decoder - Miscellaneous: This is a keypad circuit that will convert the decimal value of any keypad switchinto its BCD equivalent. __ Designed by Ron J.
Digital Keypad Combination Lock - This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be __ Designed by Aaron Cake
Digital Keypad Combination Lock - This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be __ Designed by Aaron Cake
DMX PC Keyboard Interface - This is the Design for a DMX512 to computer keyboard interface. It sits in line on the computer keyboard and on the DMX 512 chain. Decoding The Lighting data and ifone it's set channels is set above 1/2 value this unit will output a sequence of keyboard keys to the connected PC. __ Designed by Paul Harris
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