|
 |
Circuits designed by David Johnson, P.E.
Last Updated on:
Saturday, December 23, 2017 03:21 PM
List of Dave's Circuit Designs
The contents & graphics
of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB
SITE server |
|
|
|
|
More
Timer Circuits
Garage Door Timer,
May 15, 2011 The
circuit below is designed to automatically close a garage door, if it was left open
for a long period of time. A reed relay and magnet combination sense when the
door is fully open. |
|
 |
An ultra low power voltage comparator oscillator and two 74HC4040 ICs
are used to generate the time delay. A jumper or a switch can be used to
select a time of 30 minutes, one hour or two hours. The circuit draws only
about 2ua so a pair of AA alkaline cells would keep the unit running for many years. |
| Magnet
+ Reed Relay Switch |
|
|
|
Click
on Drawing Below to view PDF version of Schematic |
|
 |
|
|
|
|
