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Circuits designed by David Johnson, P.E.
Last Updated on: Wednesday, October 18, 2017 05:04 AM

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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

Garage Door Timer designed by David Johnson May 15, 2011

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