Information for V1 timer boards
Here is a picture of the bare
board and a completed board for
In order to complete the project
you will need to add the following components:
- Right angle, PC board mount DB-25 male connector (unless you buy the
kit that includes the connector)
- Five 10K-Ohm resistors (Radio Shack #271-1335, $0.99 for a 5 pack)
- Start switch
- Lane sensors (see parts list above or discussions on the forum for suggestions)
- Hookup wire for start switch and lane sensors
- +5 volt power supply
You may not need the resistors OR the 5 volt power supply if your computer
has built-in pull-up resistors. Unfortunately there is no real way to
know if your computer has the built-in resistors. Some do, some don't.
If your computer does not have pull-up resistors your timer may operate
erratically or it may give sluggish results.
Refer to the completed
board photo as necessary:
- Make sure you insert all components on the BLANK side of the board.
The side with the traces is only used to solder parts in place. There
should be no components on the solder side (the side with the traces).
- Insert the pins of the DB-25 connector through the holes and solder
the pins in place. It is not necessary to solder every pin. You
can simply solder all the pins with traces to them, plus a few on the opposite
end of the connector to help hold it in place. In order to keep the
board cost low I elected not to put a solder mask on the board. Make sure
that you don't accidentally solder bridge between two pins or between a
pin and a trace. This is especially easy to do near pin 2, pin 9, and
- Next insert the resistors into the holes in the middle of the board.
Resistors are not polarized so it doesn't matter which end goes which
way. Flip the board over and solder each resistor in place. Again, make
sure that you do not solder bridge between a pin and an ajoining trace.
Clip off any excess resistor leads that are sticking out of the back of
- Solder wires onto the ends of the phototransistors for each lane. Use
one color of wire for the emitter and a different color for the collector
on each sensor. This will make the next step MUCH easier and less
error prone. Use just enough wire to reach from the back of your PC to the
track. I would use no more than 3 to 5 feet of wire on
each phototransistor. Each sensor should have the same amount of wire
as all the others for proper timing (electricity travels about 9 inches
per nanosecond so if one wire is 9 inches shorter than another, the timing
will be off by 1 nanosecond between the two sensors). Also solder
(or otherwise attach) a wire to each side of the start gate switch. Remember
to leave enough wire to stretch all the way to the top of the track.
- Refering to the solder side of the board, note that there are 5 rows
of two holes each on the right side of the board. These are the connections
for the start gate (at the top, notice the word "start" above
the top row of holes) and the lane sensors (rows 2-5 = lanes 1-4 respectively).
On the right side of the rows is the word "emitter" which
indicates where the emitter from each sensor should be connected (the
wire from the collector goes in the other hole in each row). Flip
the board back over so you are looking at the component (blank) side and
then run the wires through the board and solder them in place making sure
to connect the emitter to the correct side on each row. Alternately,
you can solder a connector in place (as in the photo) and then connect
the wires to that so that you can attach and remove the sensors easily.
While you are at it, solder the wire from the start gate to the top
row of holes (polarity does not matter for the start gate, either wire in
either hole will work).
- Now hook up a regulated 5 volt power supply to the board. Again
refering to the solder side, note the markings for "+5" and "GND"
which indicate where the +5 line and the ground line from the power
supply should be connected. Note that the power supply is not hooked up
in the photo.
- Now, DOUBLE CHECK EVERYTHING!!! I refuse to be held responsible
for damage to your computer if you have not connected things correctly and
double checked your work. Make sure you have the +5 and ground from
the power supply connected correctly. Plug in the power supply and
check the voltages with a meter to confirm this. While you are at it, check
that the various pins on the DB-25 change state properly when you cover
and uncover the phototransistors. You should be able to check this
quite easily using a volt meter.
- ONLY after you have checked EVERYTHING and then DOUBLE
CHECKED everything should you attach the circuit to your PC. Run
the pinewood software and use the diagnostics screen to confirm that each
of the bits changes state properly when you cover and uncover each phototransistor.
Also check that the start gate switch changes states correctly. If
not, carefuly review the instructions above to make sure you haven't missed
anything. Check closely for phototransistors that are not hooked up correctly
(emitter and collector reversed).