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Keypad Circuits   Page 1
Key Pads:  #'s - C      D -H      I - L      Ms      T - Z
Last Updated on: Tuesday, August 18, 2015 06:53 AM


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

C implements pushbutton light dimmer -  06/18/98 EDN Design Idea   (Several design ideas on this page, scroll to find this one)  Four ICs--a multiplier, a sync separator, an op Amp, and a dc-restore IC--along with a handful of passive components can implement a complete AGC and dc-restore circuit for video signals (Figure 1). . .  [by William Grill, Riverhead Systems, Littleton, CO]  

 

C Provides Wireless Keypad Control -  10/08/98 EDN Design Idea   (Several Design Ideas, scroll to find this one. )  The circuit in Figure 1 is a simple, 4X4 keypad remote-control system. A 68HC705J1A C, IC1 (Figure 1a), costs less than $1 and controls the keypad functions. When you depress any key, the C provides a 4-bit hex-data output and then enables a latch signal to latch the data into IC2. Next, the C enables IC2 to transmit the signal to the IC3 encoder to convert the 4-bit hex data to serial data to send to IC4. IC4, the RF data-transmitter module, mixes the serial data with the 315-MHz carrier frequency to transmit. . .  [by Lloyd Khuc, Motorola Inc, Austin, TX]

1-wire keypad interface frees microcontroller-I/O pins -  03/31/05  EDN Design Idea   Using this interface topology, you can reduce the number of keypad interface wires to just one and thus save critical microcontroller I/O ports. . .  [by Israel Schleicher, Prescott Valley AZ]

2 Way IR Terminal -  This unit provide 2 way IR communications using a numeric keypad and an LCD display. Data is sent and received in ASCII with no regard to what the data means to any particular device. . .  [Luhan Monat - Mesa Arizona ]

 

2 wire 4 by 4 key keyboard interface saves power -  08/17/06 EDN Design Idea   Resistor matrix and microcontroller encode keypad - You 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. . .  [by Stefano Salvatori, University of Rome, Rome, Italy, and Gabriele Di Nucci, EngSistemi, Rome, Italy]

 

4 Digit Keypad -  This is an enhanced 4 digit keypad which may be used with the Modular Alarm System. .[Circuit design 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 section - to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. I used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application. . . .  [Circuit design by Ron J.]

 

4-Bit Ps A/D Converter Decodes Keypads Input -  10/13/94 EDN Design Idea   Fig 1 shows a Mitsubishi M50927-XXXSP/FP 4-bit microcontroller decoding a 44 keypad using only four digital I/O lines instead of eight. Saving four of a 4-bit C's precious I/O lines could be significant. 4-bit C's ADC provide. . .  [by Ryoden International (Shanghai) Ltd, Shanghai, China]

 

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.   . . .  [Ron J.'s circuit]

 

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. . .  [Electronic design by Ron J.]

 

5 Digit Alarm Keypad -  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. . .  [Andy Collison's website]

 

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. . . .  [Ron J.'s circuit]

 

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. . . .  [Ron J.'s circuit]

 

A 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. . .  [Electronic design by 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. . . .  [Ron J.'s circuit]

 

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) you power-up a project for the first time or soak-test a piece of equipment. . . .  [Circuit design 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]

 

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