1. Hexadecimal Keypad Hardware Description Internal Organization
Doug Butterworth AIM: Epor Phone:
Hardware Description
Internal Organization
The Circuit in Action
Signal Bouncing

2. Hardware Description:
16-Button Numeric Keypad
Rugged black plastic
4 x 4 Matrix Type
8-position solder pad
Contact rating: 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)

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

4. Circuit Diagram 1
Row 1 2 3 A

5. Hex Keypad: The Movie!

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

7. 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.

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

9. Signal Bouncing On the Keypad
(Wow!)

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