of only the results stored in the storage register. If two
shots are fired and stored, the average is of the two. If five
shots are fired and stored, the average is of the five.
Putting It Together
The templates associated with this project are
available at the article link. When called for, cut them out
and glue them to their respective parts. Drill out the holes
called for on the templates. You can then remove the
templates by using hot water. If the 1/8” drill is too tight
for the dowel, use a number 30 drill.
Solder in the pre-programmed PIC16F916 noting the
square pad is pin 1. Solder in the two switches. Solder in
C3. Solder in the two resistors and the two LEDs, noting
that the square pad is + and the long lead of the LED.
Solder in the LCD, then IC4 noting its flat.
Using the templates, drill the holes in the top of the
box for the screws and switches. Drill out the holes for the
five-pin DIN jack. Drill the screw holes with a 1/8” drill.
They will self-thread using a 1/4” 6-32 screw.
Cut the five different colored wire wrap wires to 4”
and solder to the lugs of the jack. The unit does not have
an on-off switch, but is turned on and off by plugging the
cable into the display box.
You may wonder why I didn’t use a phone jack and
cable. I tried, but the phone cord picked up too much
ambient noise and caused either sensor to fire the other
when triggered. A shielded conductor solved the problem.
The reason there’s a crazy numbing system of the jacks
and plugs is because that is what is printed on the jacks
Pin 1: Red wire from + pad (nine volts +)
Pin 2: White wire from W pad (signals
from sensor 1)
Pin 3: Short wire to pin 6 (ground)
Pin 4: Yellow wire from Y pad (signals
from sensor 2)
Pin 5: Orange wire from pad 5 (five volts regulated)
Pin 6: Green wire for - pad (battery -)
Solder the wires to the above pads. Place two 3/8”
spacers over the two holes next to the switches. Using
two 1/2” 6-32 screws, affix the board to the lid of the box.
The screws should self-thread or you can tap the board.
Screw the lid to the bottom of the box. I tacked the wires
coming from the jack to the box with hot glue to act as a
strain relief. The extra pads under the LCD are
programming pins for those who wish to change the
program (see Figure 1). The cable coming from the box is
a programming cable I used for developing the software.
The cable length is 10’. Disassemble the plugs and put
the black strain relief on each end of the cable. Strip both
ends of the wire about 1/2” and remove the tin foil. Strip
each wire 1/6” of an inch and tin. Solder the wires to the
DIN plug in the following order:
Pin 1: Red wire (nine volts +)
Pin 2: White wire (signals from sensor 1)
Pin 3: Ground wire (shield ground)
Pin 4: Yellow wire (signals from sensor 2)
Pin 5: Orange wire (five volts regulated)
As mentioned, the microprocessors are pre-programmed. Solder IC1 and IC2, noting the
square pad is pin 1. Solder in R1, R3, and
R2. R2 should be rotated so that its
adjustment is toward the bottom of the
board. Solder in C1, C2, and C3. Solder in
the photodetector. The vacant holes are for
programming the micro. The pads marked +,
- , TP1, and P (pulse) will be used later (refer
to Figure 2).
Drill a 1/4” hole in the bottom center of
the black box. Using Gorilla® glue, attach a
1/4 x 20 hex nut to the inside for the tripod
20 March 2017
■ FIGURE 1. Chronograph display.
■ Lug view.
■ Lug view
Complete kits are available through the Nuts & Volts webstore
along with all the necessary pre-programmed microcontrollers.
ExpressPCB (www.express pcb.com) was used to design the
boards and draw the schematic. These files are available along
with the microprocessor's code at the article link.