Hexadecimal Keypad Hardware Description Internal Organization Doug Butterworth Email: epor@psu.edu AIM: Epor55 Phone: 814.217.2466 Hardware Description Internal Organization The Circuit in Action Signal Bouncing

Hardware Description: 16-Button Numeric Keypad Rugged black plastic 4 x 4 Matrix Type 8-position solder pad Contact rating: 24VDC @ 20mA Contact resistance: 200 Ohms max. Life test: 1,000,000 life cycles per key Size: 3.0"L x 2.8"W x 0.6"H $7.95 from                        Links: Product Page Technical Documentation(pretty under whelming)

Internal Organization Output organization Output pin # Symbol Pin 1 Row 2 Pin 2 Row 3 Pin 3 Col 1 Pin 4 Row 4 Pin 5 Col 2 Pin 6 Col 3 Pin 7 Col 4 Pin 8 Row 1 When a button is pushed, the associated row and column pin for that button are connected together.

Circuit Diagram 1 Row 1 2 3 A

Hex Keypad: The Movie!

Uses Wired into a keypad encoder. (presentation 19 with Anthony Dotterer) Xilinx Use your imagination…

Signal Bouncing Background Theory: Nearly all mechanical switches generate some bounce. After switched, they actually open and close several times before settling down to their new position. Can Last as little as a fraction of a millisecond to as long as 50 ms. Only very high quality switches generate little or no bounce.

Signal Bouncing (Simulated by touching a wire to a alligator clip)

Signal Bouncing On the Keypad (Wow!)

How to prevent: Use an RC network to slow either the rising or falling edge of the event. Buy a really good switch!