RoboNova Tilt Sensor

S-Fd and S-Bk are two mercury tilt switches.
                                                     A/D input 
When upright, both switches are open,              = 1.56v
when on front, right switch is closed,             = 1.93v
when on back, left (purple lead) switch is closed, = 3.4v
when upside down, both switches are closed         = 0v

  _______._________ 5v
         |
         /
         \
         / 4k7
         \
         |
     ____._____.______ A/D input
    |          |
    /          /
    \          \
    / 10k      / 2k7
    \          \
    |          |
    o          o
    ./ S-Bk    ./ S-Fd
    |          |
 ___.__________.____ 0v