ELM415

Elm Electronics – Circuits for the Hobbyist

< http://www.elmelectronics.com/ >

Connection Diagram

PDIP and SOIC

(top view)

1

2

3

4

8

7

6

5

Up/Down Interface

Many modern control circuits use the value from

a digital counter to directly determine a setting or

position. Manipulating this value under computer

control is not difficult, but when one has to interface

with a human operator, several other factors must be

considered. Human interfaces often require that the

circuit respond to changes in a setting – up or down,

left or right, clockwise or counterclockwise. These

controls need a simple interface, which the ELM415

provides.

This 8 pin integrated circuit contains all the

timing and logic that is necessary to interface two

pushbuttons to most counter type interfaces. It reads

the position of the switches and translates that into

an appropriate signal for a counter to either

increment or decrement, which in turn controls the

output variable. Logic to filter out contact bounce, to

sense when both keys are pressed simultaneously,

to invert the count output, and to provide continuous

pulses if an input pushbutton stays pressed are all

included.

UpSw

Up/Down

Count

Description

• Digital audio potentiometer controls

• Variable voltage or temperature circuits

• Motor positioning controls

• Single-stepping control circuits

• Reset circuits

Applications

Block Diagram

1 of 5

• Low power CMOS design – typically 1mA at 5V

• Wide supply range – 3.0 to 5.5 volt operation

• Fully debounced switch inputs

• Internal pullup resistors provided

• Protection from simultaneous key presses

• High current drive outputs – up to 25 mA

• User selectable automatic repeat function

• Selectable Count output polarity

Features

ELM415DSA

DownSw

Repeat

Invert

5

Count

Logic

4

Invert

UpSw

7

DownSw

Debounce

Circuit

2

Up/Down

6

3

Debounce

Circuit

Latch

reset

set

Pulse

Generator

Output

Control

Repeat