ELM334
Garage Doorman
Description
The ELM334 is an integrated circuit for remotely
monitoring the position of electrical contacts (on a
garage door, for example) and reporting the position
by way of coloured LEDs. A two-wire interface is all
that is needed to convey the position of the door to
two remotely located LEDs, and to also provide
pushbutton control for an electric opener if desired.
This circuit is able to monitor the state of one or
two position sensing switches, provide debouncing
of the signals, and to generate an alternating
(flashing) output when the position changes. In
addition, there is a separate pushbutton input that
may be used to control an electric garage door
opener, or possibly trigger an alarm.
Several examples of how the ELM334 might be
used are provided in the Example Applications
section.
Features
• Low power CMOS design
• Wide supply range - 3.0 to 5.5 volt operation
• Simultaneous monitoring of three inputs
• Fully debounced inputs
• Two wire interface to LEDs
• Stuck button protection on the control output
• Pulsed control output
Connection Diagram
PDIP and SOIC
(top view)
V
DD
1
2
3
4
8
7
6
5
V
SS
OpenSw
ClosedSw
Control
Applications
• Garage door monitoring and control
• Remote signalling and acknowledgement
• Remote alarm circuits
RLED
GLED
PB
Block Diagram
V
DD
RLED
2
Debounce
Timers
Drive
Logic
V
DD
Debounce
Timers
V
DD
7
OpenSw
GLED
3
6
ClosedSw
PB
4
Debounce
Timers
Pulse
Generator
5
Control
ELM334DSC
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