2d. On the underside of the board, connect the resistors, triacs,
and ribbon cable header following the schematic. I simply bent and
soldered down the uncut leads, rather than the usual method of
trimming leads and connecting with insulated wire. Apologies to
any professional electrical engineers who are nauseated by this.
2e. Connect the speedometer sensor’s 2 wires to power (5V)
and one of the Arduino’s interrupt pins, D2 or D3 (I used D3).
Also tie that same pin to ground with the 1kΩ resistor; otherwise,
your sensor might detect nonexistent ghost bikes in your vicinity.
Different ProtoShields have different layouts, so you should make
these connections wherever it makes sense for your board.
On the one shown here, made by MAKE intern Kris Magri, the
speedo connects to one end of the 5V rail and an adjacent hole,
which is wired up to D3 on the underside. The 1kΩ resistor fits
into the row of 100Ω resistors and connects to ground.
On my v. 1 ProtoShield, the power, ground, and D3 pins all sit on
the BlueSMiRF header, so I plugged the speedo in there. This
project doesn’t use Bluetooth, and the BlueSMiRF header was
a handy place to connect.
2f. Connect the EL wire power supply’s black wire to the board’s
ground rail and its red wire to both adjacent pins at the end of the
ribbon header, bridging the 3 pads underneath. This divides the
power so that one ribbon wire feeds the left digit and the other
feeds the right.
2g. Use electrical tape to insulate all exposed conductors, and
shrink any heat-shrink tubing you’ve applied.
2h. Solder one lead from each digit (either lead) to individual wires of the ribbon cable. These are the
grounds. You can be systematic and plan ahead which pin goes to which numeral, but we decided not
to keep track and to make the associations later in the software.