|Problem: Need circuit to automatically close the garage door after it is left open for a given period of
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 timer. The 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.
This commercial devices, shown above, contains a battery powered circuit which uses a tilt switch to
detect the horizontal orientation of the garage door. It has a timer and a RF
transmitter to send a command to the opener to close the door after a period of time.