Circuits for photocell lego tank, Jim Mahoney, Oct 2012


=== left motor driver (see e.g. http://embedded-lab.com/blog/?p=1159 )

                                   ---| diode >|----
                                   |               |
                            /--------[ DC motor ] ------[ 9V DC ]
                            |NPN
   arduino ---[ 1K Ohm] --- |transistor
   PWM out                  \------------[ground]
   pin 9


=== right motor driver
                                   ---| diode >|----
                                   |               |
                            /--------[ DC motor ] ------[ 9V DC ]
                            |NPN
   arduino ---[ 1K Ohm] --- |transistor
   PWM out                  \------------[ground]
   pin 11


=== left photocell (voltage divider; see http://learn.adafruit.com/photocells )

                     ---[ photocell ]---[ 5V DC]
                     |
   arduino ----------|
   analog in         |
   pin A1            ---[ 10K Ohm]------[ ground ]


=== right photocell (voltage divider)

                     ---[ photocell ]---[ 5V DC]
                     |
   arduino ----------|
   analog in         |
   pin A3            ---[ 10K Ohm]------[ ground ]

=== push button (see http://www.ladyada.net/learn/arduino/lesson5.html )

                                  -----[ switch ]---[ 5V DC]
                                  |
   arduino ---------[ 100 Ohm] ---|
   digital in                     |
   pin 2                          -----[ 10K Ohm ]---[ ground]