garage door reaches the top of its travel, it pushes against
the left end of the music wire which rotates the shaft of
SW2 by 90 degrees, causing it to close. When SW2
closes, it grounds the reset pin of the 4060 allowing the
count to start from zero.
I built the closer circuit on a small perf board
(RadioShack 276-148) shown in Figure 4. The perf board
and the manual controls were installed in a small ( 2. 5 x 2
x 1.5 inch) aluminum project box that I mounted on my
garage wall (Figure 5). This was a fun project to build. It’s
actually useful and it doesn’t even use a microcontroller!
Building Your Own
If you are thinking of building your own garage door
closer circuit, here are some things you should consider:
■ FIGURE 4. Garage door closer circuit mounted inside a
did not exceed the maximum operating voltage. When I
want to keep the garage door open for an extended
period — like when I am mowing the lawn or washing the
car — I can flip switch SW1 to the disable position. This
removes power from the closer circuit and lights a red
LED warning me the closer is disabled. Even when the
closer circuit is disabled, the garage door can still be
opened or closed by pressing pushbutton PB1. When you
think about it, the closer circuit is nothing more than a
fancy way of pressing the local pushbutton (PB1).
One thing I haven’t mentioned yet is how the closer
circuit detects when the garage door is open. This is done
via switch SW2 shown in Figure 3. I am using a normally-open rotary switch connected to a piece of music wire.
When the garage door is closed, SW2 is open and the
reset pin of the 4060 is pulled high by R1. When the
■ FIGURE 5.
• Check the voltage and current available at your
automatic garage door operator’s local pushbutton.
Depending on the voltage available, you may want to use
a 78L12 or 78L05 instead of the 78L15.
• Determine the voltage and duration of the pulse
needed to trigger your automatic garage door operator;
mine was 0.3V or less for 100 milliseconds.
• Note that a CMOS 4060 can operate from three to
15 volts. A 74HC4060, on the other hand, can operate
from two to six volts.
• The closing time for my circuit varies from three
minutes and 15 seconds in the summer to three minutes
and 45 seconds in the winter. I did not use temperature
stable components. If you want a more consistent closing
time, use temperature stable precision components for Ct
• Shorter closing delays can be achieved by using one
of the 4060’s less significant outputs — like Q12 or Q10 —
or by increasing the frequency of the oscillator.
• Longer closing delays can be obtained by
connecting the Q14 output of the 4060 to the clock input
of another counter — like a 4040, 12-stage binary counter.
If you do this, be sure to connect the reset pin of the
4040 to the reset pin of the 4060 so both chips start
counting from zero.
• I used a rotary
microswitch to detect
the garage door was
open because I
happened to have it
available. A magnetic
switch — like those used
as door and window
sensors in alarm systems
— would probably be
more reliable in the
QTY PART REFERENCE
1 100 µF, 35V C1
1 0.1 µF, 35V Ct
2 100K, 0.25W, 5% R1, Rt
1 2.2M, 0.25W, 5% R2
1 4.7K, 0.25W, 5% R3
1 1K, 0.25W, 5% R4
1 1N4001 D1
1 LED, red D2
1 2N3904 Q1
1 78L15 U1
1 4060 U2
1 DPST toggle SW1
1 Door sensor SW2
1 Pushbutton PB1
Hope you find this
circuit as handy as I do.