diodes in place on the board first, observing the
polarities of the diodes. Next, solder the ICs, followed by
the jumper terminals, then the FET transistors, and the
battery snap wires with appropriate lengths to the off-board reset switch, input devices, and buzzer. Although I
allowed for it, I didn’t install a buzzer. If you prefer not to
install one, then you don’t have to solder FET T3 in place.
Now, insert the seven-segment displays onto the
circuit board from the foil side. With this side of the
board facing you, pin 1 [e] is indicated to the left and the
seven-segment display should be inserted with the
decimal point [DP] to the bottom right. Check all
soldering connections, etc., before inserting the battery.
The reset button is also the off button, and all displays
will turn off for storage.
If all wiring is correct, press the
reset button. All displays should be
off. Activate any of whatever
device input medium is used, and a
number 1 should appear on that
input display. Repeated activation
on any same input device should
do nothing more.
Now, activate any other input
device and a number 2 should
appear on its associated display,
and so on for all the other displays.
Pressing the reset button clears all
the displays; the unit is ready for
more use or can be placed in
The input device option that
you choose will most likely
determine your connection
method. I would suggest using
RCA plugs/jacks to provide for a
solid and bounce-free connection.
Not only would it be an easy
but both are readily available with
pre-assembled male-end cables in
The Finish Line
Hopefully, you will have a fun
application for this project and find
many ways to use it.
Perhaps in a future article, I’ll
cover adding a timer feature if
there is enough interest. Files to
make your own circuit boards are
available at the article link. Feel
free to contact me with questions.
32 March 2014